Dissertations / Theses on the topic 'Polymerization induced phase separation'
To see the other types of publications on this topic, follow the link: Polymerization induced phase separation.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Polymerization induced phase separation.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Oh, Junsuk. "Computational simulation and morphological analysis of polymerization-induced phase separation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0031/MQ64240.pdf.
Full text
2
Luo, Xiaofan. "Polymerization induced phase separation (PIPS) in epoxy/poly([epsilon]-caprolactone) systems." online version, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=case1189443918.
Full text
3
Luo, Xiaofan. "Polymerization Induced Phase Separation (PIPS) in Epoxy / Poly(ε-Caprolactone) Systems." Case Western Reserve University School of Graduate Studies / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=case1189443918.
Full text
4
Gao, Ziyao. "Study of Shape Memory Polymer Composites from Polymerization Induced Phase Separation Process." Thesis, University of Louisiana at Lafayette, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10681918.
Full textAbstract:
Polymer composites are taking the place of traditional materials in many fields. They are preferred in engineering structures due to the advantages in strength, stiffness, thermostability, corrosion resistance, and ductility at high temperatures. Study of PCL-based shape memory polymer composite can expand its application. And in order to fully understand SMP properties, a series of comprehensive testing is required.
Samples with different PCL percentages must be made by using a standard and optimized procedure to eliminate unwanted variables, and to ensure the amount of PCL in samples is the only variable.
The DSC test on the SMP samples shows that there are two transition phases. One is at 53 °C and indicated as PCL melting temperature; another one is at 138.5 °C, indicated to be the glass transition phase.
Shape memory behavior tests on the SMP samples show that the PCL-based polymer composite has significant shape recovery ability. The ability of recovery is proportional with the amount of PCL in the sample. And the recovery performance is shown in both strain and stress recovery.
The mechanical properties of SMP composite are determined by compression tests. Tests are performed on each specimen with different PCL percentages. The maximum compressive stress is higher in specimens that have a higher amount of PCL, and this result agrees with results from the shape memory test.
Finally, the SMP composites are observed with SEM. A unique globule structure is shown in the specimens regardless of their PCL percentages. This globule structure is totally different from the structure in pure epoxy. The reason for this difference is still unknown and needs to be determined with further research.
5
Lee, Jeongwoo. "Fabrication of polymer/metal oxide composites through polymerization-induced phase separation and characterization of their mechanical and electrochemical properties." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1446217264.
Full text
6
Elhaj, Ahmed. "Porous Polymeric Monoliths by Less Common Pathways : Preparation and Characterization." Doctoral thesis, Umeå universitet, Kemiska institutionen, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-89322.
Full textAbstract:
This thesis focuses on my endeavors to prepare new porous polymeric monoliths that are viable to use as supports in flow-through processes. Polymer monoliths of various porous properties and different chemical properties have been prepared utilizing the thermally induced phase separation (TIPS) phenomenon and step-growth polymerization reactions. The aim has been to find appropriate synthesis routes to produce separation supports with fully controlled chemical, physical and surface properties. This thesis includes preparation of porous monolithic materials from several non-cross-linked commodity polymers and engineering plastics by dissolution/precipitation process (i.e. TIPS). Elevated temperatures, above the upper critical solution temperature (UCST), were used to dissolve the polymers in appropriate solvents that only dissolve the polymers above this critical temperature. After dissolution, the homogeneous and clear polymer-solvent solution is thermally quenched by cooling. A porous material, of three dimensional structure, is then obtained as the temperature crosses the UCST. More than 20 organic solvents were tested to find the most compatible one that can dissolve the polymer above the UCST and precipitate it back when the temperature is lowered. The effect of using a mixture of two solvents or additives (co-porogenic polymer or surfactant) in the polymer dissolution/precipitation process have been studied more in depth for poly(vinylidine difluoride) (PVDF) polymers of two different molecular weight grades. Monolithic materials showing different pore characteristics could be obtained by varying the composition of the PVDF-solvent mixture during the dissoluteion/precipitation process. Step-growth polymerization (often called polycondensation reaction) combined with sol-gel process with the aid of porogenic polymer and block copolymer surfactant have also been used as a new route of synthesis for production of porous melamine-formaldehyde (MF) monoliths. In general, the meso- and macro-porous support materials, for which the synthesis/preparation is discussed in this thesis, are useful to a wide variety of applications in separation science and heterogeneous reactions (catalysis).
7
Venkateshan, Karthik Johari G. P. "Polymerization and phase separation studies in liquids." *McMaster only, 2006.
Find full text
8
Jordan, Alexander Thomas. "Liquid phase plasma technology for inkjet separation." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47543.
Full textAbstract:
Currently most deinking technologies are dependent upon flotation and dissolved air flotation
(DAF) technology in order to separate inkjet ink from fiber and water. Much of this
technology is based on ink that is extremely hydrophobic. This made flotation and DAF
very easy to use because the ink in the water would very easily move with the air in flotation
and be brought to the surface, after which the ink can be skimmed and the pulp can
be used.
Now that small scale printing has become the norm, there has been a move to high
quality, small scale printing. This involves the use of a hydrophilic ink. Hydrophilic ink
cannot be easily separated from water and fiber the same way the hydrophobic ink can be.
With low concentrations of hydrophilic ink in the process water stream, it can be absorbed
into the process but as the hydrophilic ink concentration rises alternative methods will be
needed in order to separate inkjet ink from water.
One solution is to find a method to effectively increase ink particle size. This will
enable the ink particles to be filtered or to have an increase ecacy of removal during
flotation. In this thesis, one solution is discussed about how electric field and electric
plasma technologies can be used to increase particle size and help purify process water in
recycle mills.
This plasma treatment can very effectively bring ink particles together so that they may
be separated by another method. There are two methods by which this may take place. One
is polymerization and the other is electro-coagulation. These processes can work side by
side to bring ink particles together.
This plasma treatment process creates free radicals by stripping off hydrogen atoms
from surrounding organic matter. These free radicals then react with the high alkene bond
content within the ink to create a very large covalently bonded molecule. This is the new
mechanism that is being investigated in this thesis. The other action that is taking place is electro-coagulation.
Plasma treated ink can be filtered out using a cellulose acetate or cellulose nitrate membrane
or they can be filtered using paper or fiber glass filters as well. The extent at which
these can be filtered out is dependent on the size of the pores of the filter. In this study, it
was shown that the plasma treatment was able to clean water with a fairly small amount
of energy. It was also found that treatment time and concentration had very little eect on
the outcome of the treatment ecacy. One factor that did have an effect was the pH. At
very high pH values the process became noticeably less eective. The high pH essentially
eliminated the electro-coagulation aspect of the treatment process and also hurt the polymerization
aspect as well because of lower amount of hydrogen atoms available for the
plasma to create free radicals.
A model of the process was used to try to give the reader an idea of the ecacy that the
process would have in an industrial scale process. The model assumes that two types of ink
particles exist. One is ink that has a radical and another in which the ink does not have a
radical. The model also assumes that if ink is at all polymerized, ink is filtered out with the
0.8 micron filter. The model assumes three reactions; initialization, propagation and partial
termination. The partial termination is a result from the general chemical structure of ink.
Ink has many double bonds in its general structure which makes termination very unlikely
to occur, so the model assumes that on average when two radials interact that only one is
eliminated. This model is only supposed to give the reader an idea of the ecacy of the
process. The numbers provided in the model will change very significantly in a different
system.
The evidence behind polymerization aspect of the process comes from two main sources.
One is the small molecule analysis from methanol after being exposed to the plasma and the
other from the plasma being exposed to allyl alcohol. The small molecule analysis shows
that the process generates free radicals on organic molecules. Methanol was exposed to
the plasma and then the resulting GC/MS analysis showed that 1,2-ethanediol was present, this showed that the electric discharge process was able to create free radicals on organic
molecules in the liquid phase.
Using a similar process the plasma discharge process was exposed to a mixture of allyl
alcohol, water and propanol and water in two separate experiments. The difference between
these two molecules is an alkene bond that is between the carbon two and carbon three
atoms. The particle size of both samples was then analyzed and it was shown that the
solution with allyl alcohol had an average particle size about an order of magnitude larger
than the solution with propanol in it.
Because of all the evidence discussed here and in the rest of the thesis we believe that
the plasma treatment of ink has both polymerization and electro-coagulation aspect. This
process could also be a potential solution to the water soluble ink problem that will soon
face the recycling industry.
9
Kulkarni, Amit. "Reaction induced phase-separation controlled by molecular topology.*." Cincinnati, Ohio : University of Cincinnati, 2004. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1108001435.
Full text
10
Munshi, Imran. "Reaction-induced phase separation in modified epoxy resins." Thesis, University of Manchester, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493906.
Full textAbstract:
Studies have been carried out on reaction-induced phase separation in epoxy networks, formed from a DGEBA-type epoxy resin prepolymer, DER332, and m-xylylene diamine, MXDA, containing as modifiers either (i) butyl laurate (B) or (ii) m-cardura (C), (synthesised from Cardura El0 and 2-ethyUiexanoic acid). The reactants and modifiers were characterised using end-group analysis, Fourier transform infra-red spectroscopy (FTIR), differential scanning calorimetry (DSC), nuclear magnetic resonance and viscometry.
11
KULKARNI, AMIT S. "REACTION INDUCED PHASE-SEPARATION CONTROLLED BY MOLECULAR TOPOLOGY." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1108001435.
Full text
12
Tabatabaei, Fatemeh, and Gunter M. Schütz. "Nonequilibrium field-induced phase separation in single-file diffusion." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-194414.
Full textAbstract:
Using an analytically tractable lattice model for reaction-diffusion processes of hard-core particles we demonstrate that under nonequilibrium conditions phase coexistence may arise even if the system is effectively one-dimensional as e.g. in the channel system of some zeolites or in artificial optical lattices. In our model involving two species of particles a steady-state particle current is maintained by a density gradient between the channel boundaries and by the influence of an external driving force. This leads to the development of a fluctuating but always microscopically sharp interface between two domains of different densities which are fixed by the boundary chemical potentials. The internal structure of the interface becomes very simple for strong driving force. We calculate the drift velocity and diffusion coefficient of the interface in terms of the microscopic model parameters.
13
Tabatabaei, Fatemeh, and Gunter M. Schütz. "Nonequilibrium field-induced phase separation in single-file diffusion." Diffusion fundamentals 4 (2006) 5, S. 1-38, 2006. https://ul.qucosa.de/id/qucosa%3A14278.
Full textAbstract:
Using an analytically tractable lattice model for reaction-diffusion processes of hard-core particles we demonstrate that under nonequilibrium conditions phase coexistence may arise even if the system is effectively one-dimensional as e.g. in the channel system of some zeolites or in artificial optical lattices. In our model involving two species of particles a steady-state particle current is maintained by a density gradient between the channel boundaries and by the influence of an external driving force. This leads to the development of a fluctuating but always microscopically sharp interface between two domains of different densities which are fixed by the boundary chemical potentials. The internal structure of the interface becomes very simple for strong driving force. We calculate the drift velocity and diffusion coefficient of the interface in terms of the microscopic model parameters.
14
Park, Heungsup. "Toners for xerographic textile printing produced via thermally induced phase separation." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/10005.
Full text
15
Batarseh, Melanie Turkett. "Formation of anisotropic hollow fiber membranes via thermally induced phase separation /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
Full text
16
Garg, Nandita. "Polymer shielded dye-affinity chromatography and temperature induced phase separation two strategies to simplify protein affinity separation processes /." Lund : Dept. of Biotechnology, Lund University, 1995. http://books.google.com/books?id=Qw5rAAAAMAAJ.
Full text
17
Yahata, Yoshikazu. "Extended Design of Concentrated-Polymer-Brush-Decorated Hybrid Nanoparticles and Their Use for Phase-Separation Control." Kyoto University, 2018. http://hdl.handle.net/2433/232486.
Full text
18
Murase, Hiroki. "Flow-induced phase separation and crystallization in semidilute solutions of ultrahigh molecular weight polyethylene." 京都大学 (Kyoto University), 2005. http://hdl.handle.net/2433/144863.
Full text
19
Rasouli, Tezangi Ghoncheh. "Structure and kinetics of pressure-induced phase separation in polyolefin solutions and its acoustic detection." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121396.
Full textAbstract:
This thesis uses theory and simulation to elucidate the fundamental principles and key mechanisms that govern demixing in compressible polyolefin solutions and its detection using acoustic wave propagation. Demixing by pressure-induced phase separation and its acoustic detection has direct applications to the industrial manufacturing of polyethylene based on the solution polymerization process, and is an evolving area of fundamental polymer thermodynamics.The two models developed, implemented and analyzed in this thesis for the structure and kinetics of pressure-induced phase separation in compressible polymer solutions and its acoustic detection, integrate total mass, component mass, momentum with the Sanchez-Lacombe equation of state, Newtonian and Maxwellian rheological equations and generalized the Fick's flux equations that include compressibility. Heat transport is also included in the acoustic modeling.The one-dimensional early stage of pressure-induced phase separation by spinodal decomposition is sequentially analyzed for inviscid, viscous, and viscoelastic compressible fluids to elucidate the roles of viscous dissipation and polymer elasticity. This thesis results reveal the unique nature of compressible spinodal decomposition through the coupling of density and polymer concentration, giving rise to a novel acousto-spinodal decomposition process. At low compressibility, density standing waves couple with demixing, giving rise to oscillatory spinodal modes with spatial and temporal periodicities; these results were established using dynamical systems tools showing the coexistence stable and unstable critical points, which are the basis of complex dynamics and chaos. The kinetics of demixing decreases with compressibility and viscosity and increases with polymer elasticity. The structure is analyzed and validated with structure factor calculations. Scaling relations for structure and kinetics are summarized to facilitate future practical applications.A linear model of acoustic detection of spinodal decomposition is formulated and implemented by calculating the effect of increased proximity to the spinodal line in a stable compressible visco-elasto-thermo-diffusional fluid on the frequency dependence of sound propagation speed and attenuation. The acoustic response generalizes previous models by coupling viscoelasticty and diffusional processes that change as pressure decreases towards demixing. Signatures of phase separation in phase speed and attenuation are established. The results of this thesis establishes that ultimately, acousto-SD in compressible polymer solutions, integrating density waves into mass transfer processes offer new routes to tailor polymer microstructures, polymer processing and acoustic polymer characterization.Cette thèse utilise la théorie et la simulation pour éclaircir les principes fondamentaux et les mécanismes clés qui déterminent la démixtion dans les solutions de polyoléfines compressibles et sa détection à l'aide de propagation de l'onde acoustique. La démixtion par séparation de phase induite par la pression et sa détection acoustique a des applications directes à la fabrication industrielle de polyéthylène sur la base de la procédure de polymérisation en solution, et est un domaine d'évolution dans la théorie des polymères thermodynamiques.Les deux modèles, mis en œuvre et analysés dans cette thèse pour la structure et la cinétique de séparation de phase induite par la pression dans les solutions de polymère compressible et sa détection acoustique, intègrent la masse totale, la masse des composants, la lancée avec l'équation Sanchez-Lacombe de l'Etat, les équations rhéologiques Newtonienne et Maxwelliennes et les équations généralisé de flux de Fick qui incluent la compressibilité. Le transport de la chaleur est également inclus dans la modélisation acoustique. Le premier stade à une dimension de la séparation de phase par l'induction de pression par la décomposition spinodale est analysé séquentiellement pour fluides non-visqueux, visqueux et fluides viscoélastiques compressibles afin d'élucider les fonctions de la dissipation visqueuse et l'élasticité de polymère. Les résultats de cette thèse révèlent le caractère unique de la décomposition spinodale compressible par le couplage de la densité et la concentration du polymère, ce qui donne lieu à un nouveau processus de décomposition acousto-spinodal. A faible compressibilité, les vagues stationnaires de densité se couplent avec la démixtion, donnant lieu à des modes spinodaux oscillatoires avec périodicités spatiales et temporelles; ces résultats ont été établis à l'aide des outils de systèmes dynamiques montrant la coexistence des points critiques stables et instables qui est la base de la dynamique et le chaos complexes. La cinétique de la démixtion diminue avec la compressibilité et la viscosité et augmente avec l'élasticité du polymère. La structure est analysée et validée par des calculs du facteur de structure. Les relations d'échelle pour la structure et la cinétique sont résumées afin de faciliter les applications pratiques futures.Un modèle linéaire de détection acoustique de la décomposition spinodale est formulé et implémenté par le calcul de l'effet d'augmentation de la proximité de la ligne spinodale dans un fluide visco-élasto-thermo-diffusionnel compressible stable sur la dépendance en fréquence de la vitesse de propagation et l'atténuation du son. La réponse acoustique généralise les modèles précédents par le couplage de viscoélasticité et le processus de diffusion qui change avec la diminution de pression vers la démixtion. Les signatures de la séparation de phase dans la vitesse de phase et l'atténuation sont établies.Les résultats de cette thèse établit qu'éventuellement, acousto-SD dans les solutions polymères compressibles intégrant des ondes de densité dans les processus de transfert de masse, offre de nouvelles pistes à préparer sur mesure les polymers microstructures, le traitement des polymères et la caractérisation des polymères acoustiques.
20
Kahrs, Catharina [Verfasser]. "Investigations on the formation of porous membranes during non-solvent induced phase separation / Catharina Kahrs." Hannover : Gottfried Wilhelm Leibniz Universität Hannover, 2020. http://d-nb.info/121436716X/34.
Full text
21
Ghanbar, H. "Fabrication of porous particulate scaffolds using electrohydrodynamics and thermally induced phase separation for biomedical engineering applications." Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1460533/.
Full textAbstract:
The availability of forming technologies able to mass produce porous polymeric microspheres with diameters ranging from 150 to 300 µm is significant for some biomedical applications where tissue augmentation is required. Moreover, appropriate assembly of microspheres into scaffold is an important challenge to enable direct usage of the scaffolds in chronic wound treatments. In this thesis, the feasibility of the electrohydrodynamic (EHD) atomization forming combined with thermally induced phase separation (TIPS) for production of such drug delivery carriers, using biodegradable polymers (poly (lactic-co-glycolic acid) and poly (ε-caprolactone)) was explored. To achieve this goal, the first part of the thesis describes comprehensive parametric mode mappings of the diameter distribution profiles of the microspheres obtained over a broad range of key processing parameters and correlating this with the material parameters of five different polymer solutions of various concentrations. Based on the mode mapping studies, combination of poly (lactic-co-glycolic acid) (PLGA) and dimethyl carbonate (DMC) was found to be ideal for generating the microspheres within the targeted diameter range (150-300 µm). Surface porosity was achieved by electrospraying the PLGA/DMC solution and collecting the required size of the polymer particles in liquid nitrogen followed by lyophilisation. The second aim of this thesis was the in vitro release studies. In order to conduct this part of the study, the single needle and co-axial needle EHD/TIPS methods were used to generate the dye loaded microspheres of the required size. Three different dyes (Erythrosin B, Pyronin B and Reichardt’s) were selected as model drugs to be encapsulated separately in the produced microspheres. The purpose of selecting three different dyes was to have a prediction on the release profile of immunosuppressants with high toxicity used for treatment of chronic wounds such as perianal fistulae. The in vitro release studies showed that the dyes were released with the high initial burst release phase in 3.5-5.5 hours followed by a long and sustained release phase (in 30-360 hours). Systematic investigations using different external stimuli such as temperature, fresh media and sonication exposure was also carried out to observe their effects on the release rate of the encapsulated materials from the produced microspheres. The results acquired from the in vitro release studies showed that the temperature variations and the sonication with different frequencies have significant effects on the release rates of the incorporated materials from the polymeric microspheres. Moreover, the results demonstrated that the products collected by the single needle EHD/TIPS method is more capable of releasing the payload in a longer period of time with more sustained manner compared to their counterparts obtained from the co-axial needle method.
22
Nascimento, de Andrade Fabiana. "Effect of condensable materials during the gas phase polymerization of ethylene on supported catalysts." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1016/document.
Full textAbstract:
Les réacteurs à lit fluidisé (FBR) constituent la seule technologie viable sur le plan commercial pour la production de polyéthylène en phase gaz, car la polymérisation est hautement exothermique et le FBR est le seul type de réacteur en phase gaz offrant des possibilités suffisantes de transfert de chaleur. La nature hautement exothermique de cette polymérisation pose effectivement de nombreux problèmes pour le fonctionnement en phase gaz et peut limiter la production de certains procédés. Au cours des dernières années, les procédés en lit fluidisé ont été améliorés par de nouvelles technologies. En particulier, l'ajout d'hydrocarbures inertes (généralement liquides) permet d'augmenter la quantité de chaleur évacuée du réacteur. Ces composés augmentent la capacité calorifique de la phase gazeuse et, s’ils sont injectés sous forme liquide, s’évaporent également et absorbent ainsi encore plus efficacement la chaleur du milieu réactionnel. C’est ce qu’on appelle le fonctionnement en mode condensé. On y utilise des composés qui peuvent être liquéfiés dans le condenseur de recyclage et qui sont appelés agents de condensation induits (en anglais : Induced Condensing Agents - ICA). L’utilisation de l’ICA est extrêmement importante d'un point de vue industriel. L’injection d’ICA peut avoir de nombreux effets physiques différents au niveau des particules de polymère en croissance. Par exemple, l’ajout de ces composés peut entraîner des modifications de la solubilité et d’autres propriétés physiques, ce qui peut faciliter le transport de l’éthylène et de l’hydrogène vers les sites actifs des catalyseurs. Il est donc très important que les phénomènes physiques liés à l'équilibre de sorption entre la phase gaz et la phase polymère du ou des monomères et d'autres espèces, ainsi que leur diffusion dans la matrice polymère au niveau des sites actifs, soient pris en compte. En plus d'avoir un effet sur la cinétique, ces phénomènes peuvent également impacter la structure des molécules de polymère et par conséquent changer les caractéristiques du polymère. Identifier le comportement de ces phénomènes dans les conditions de la procédé et les variables de contrôle du rapport hydrogène / éthylène et du rapport comonomère / éthylène avec l'ICA sont les objectifs centraux de cette étude. Une série d’homo- et co-polymérisations d’éthylène en phase gazeuse a été réalisée en utilisant un catalyseur commercial Ziegler-Natta en présence de l’ICA (propane, n pentane et n-hexane). Nous avons étudié l’effet des températures, de la pression partielle de l’ICA, de l'hydrogène et des comonomères sur le comportement de la polymérisation. Il a été constaté que l’ajout de l’ICA augmentait significativement la vitesse de réaction ainsi que les poids moléculaires moyens à une température donnée. De manière inattendue, il a également été observé que l’augmentation de la température du réacteur en présence d’ICA entraînait en réalité une diminution de la vitesse de réaction globale. Ces résultats ont été attribués à l’effet de cosolubilité. Dans les réactions en présence de différentes concentrations en hydrogène, pour un rapport ICA/C2 beaucoup plus grand que le rapport H2/C2, l'effet de l’ICA sur la solubilité de l’éthylène peut compenser la diminution en taille des molécules provoquée par la présence d’hydrogène. L’impact de l’ICA sur les taux de réaction de copolymérisation est plus prononcé aux stades initiaux, perdant de son efficacité en raison de l'effet de comonomère. Enfin, une évaluation de la cinétique de cristallisation dans des conditions isothermes pour des mélanges de différentes concentrations ICA: HDPE a montré que le temps de cristallisation est significativement plus long pour les systèmes riches en ICA que pour les polymères secsFluidized bed reactors (FBR) are the only commercially viable technology for the production of polyethylene in the gas phase since the polymerization is highly exothermic and the FBR is the only type of gas phase reactor that offers adequate possibilities of heat transfer. The highly exothermic nature of this polymerization effectively poses many problems for gas phase operation and can limit the production of a certain process. However, in recent years the fluidized bed processes have been improved with new technologies. In particular, the addition of inert (usually liquefied) hydrocarbons allows one to increase the amount of heat removed from the reactor. These compounds increase the heat capacity of the gas phase and, if injected in liquid form, also evaporate and thus absorb even more heat from the reaction medium efficiently. This is known as a condensed mode operation. In it, one uses compounds that can be liquefied in the recycle condenser, and which are called Induced Condensing Agents (ICA). The use of ICA is extremely important from an industrial point of view. The injection of ICA can have many different physical effects at the level of the growing polymer particles. For instance, adding these compounds can cause changes in solubility and other physical properties, which can facilitate the transport of ethylene and hydrogen to the active sites of the catalysts. It is thus very important that the physical phenomena related to the sorption equilibrium of the monomer(s) and other species from the gas phase to the polymer phase, and their diffusion on the polymer matrix at the active sites should be accounted for. In addition to having an effect on the kinetics, these phenomena can also impact the structure of the polymer molecules and consequently qualify the characteristics of the polymer. Identifying the behavior of these phenomena under process conditions and control variables of the hydrogen/ethylene ratio and the comonomer/ethylene ratio with ICA are central objectives of this study. A series of ethylene homo- and co-polymerizations in the gas phase were carried out using a commercial Ziegler-Natta catalyst in the presence of ICA (propane, n-pentane, and n-hexane). We investigated the effect of temperatures, the partial pressure of ICA, hydrogen, and comonomers on the behavior of the polymerization. It was found that adding ICA significantly increased the reaction rate and average molecular weights at a given temperature. It was also unexpectedly observed that increasing the reactor temperature in the presence of an ICA actually led to a decrease in the overall reaction rate. These results were attributed to the socalled cosolubility effect. In reactions in the presence of different hydrogen concentrations, for an ICA/C2 ratio much larger than the H2/C2 ratio, the effect of ICA on ethylene solubility can counteract the decrease in average molecular weight caused by the presence of hydrogen. The impact of ICA on the rates of copolymerization reactions is more pronounced in the initial stages, losing strength due to the effect of the comonomer. Finally, an evaluation of the kinetics of crystallization under isothermal conditions for mixtures of different ICA:HDPE concentrations showed that the crystallization time is significantly higher for systems rich in ICA than for dry polymer
23
Martinavičius, Andrius. "Structural and transport property changes in austenitic stainless steel induced by nitrogen incorporation." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-68719.
Full textAbstract:
The saturation of the near surface layers of metals with different elements is a powerful tool to change their surface properties. In this work, structure and transport changes induced by incorporation of large amounts of nitrogen at moderate temperatures (∼370−430°C) in austenitic stainless steel are investigated. The structural study of the plasma nitrided ASS has been carried out using a combination of global (X-ray diffraction, nuclear reaction analysis) and local probe techniques (Mossbauer, X-ray absorption near edge structure, extended X-ray absorption fine structure spectroscopies). It reveals that nitriding at moderate temperatures (∼400°C) results in the nitrided layer with Fe, Cr and Ni being in different local chemical environments: Cr in the CrN-like state, Fe in the Fe4N-like state, Ni in the metallic state. The results demonstrate that the incorporation of interstitial nitrogen destabilizes homogeneous distribution of the ASS constituents, which leads to the segregation of the elements into small zones rich in Cr and Ni and provide strong evidence that the decomposition is of a spinodal nature. These experimental findings contradict the widely accepted view that the phase formed during nitriding at moderate temperatures is a homogeneous supersaturated nitrogen solid solution.
The nitrogen atomic transport study has been carried out by using ion beam nitriding of single-crystalline stainless steel, and the issues of the influence of the crystalline orientation, nitriding temperature, ion flux and ion energy are addressed. The diffusion coefficients have been extracted from the fitting of the nitrogen depth profiles by using the trapping-detrapping model. It is shown that the crystalline orientation plays a significant role in nitrogen diffusion: the penetration depth is largest, intermediate and lowest for the (001), (110) and (111) orientation, respectively. The pre-exponential factor D0 varies by two orders of magnitude depending on the orientation, while the activation energy E is similar (∼1.1 eV) for the (111) and (110) orientations and higher for the (001) orientation (∼1.4 eV). It is found that the nitrogen ion energy and the flux have the effect on the nitrogen transport in the bulk with higher energies (or fluxes) showing larger diffusion coefficients. The ion energy effect is more pronounced for the (001) than for the (111) orientation, while the flux effect is similar in both orientations. In addition, the diffusivity during post-nitriding thermal annealing without ion irradiation is found to be independent of the crystalline orientation. The observed radiation enhanced diffusion and anisotropy are discussed on the basis of nitrogen incorporation induced changes in the matrix structure (ASS decomposition and formation heterogeneous structure), ion bombardment induced effects (defects, localized vibrations) and correlated diffusion.
24
Li, Chia-Ling. "Preparation of poly(vinylidene fluoride) (PVDF) membrane by nonsolvent-induced phase separation and investigation into its formation mechanism." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20155.
Full textAbstract:
Cette thèse décrit comment la morphologie et le polymorphisme de membranes en fluorure de poly(vinylidène) (PVDF) préparées par séparation de phase induite par la vapeur d'eau (VIPS) et par un non-solvant liquide peuvent être ajustés par la température à laquelle le PVDF est dissous (Tdis) pour former la solution de coulée. Les résultats montrent que Tdis présente une transition, notée comme la température de dissolution critique (Tcri), à partir de laquelle la morphologie et le polymorphisme des membranes changent radicalement. Ce phénomène observé pour les trois solvants, N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc), and N,M-dimethylformamide (DMF), et les non-solvants (eau et une série d'alcools) utilisés dans cette étude peut être considéré comme général. La cristallisation a lieu avant la démixtion L-L quelle que soit Tdis. Pour une Tdis supérieure à Tcri, les membranes se présentent sous forme de nodules (cristallite forme beta) dont la taille décroît lorsque Tdis diminue. Ce domaine a été dénommé "à grossissement libre" car les chaînes de polymère peuvent cristalliser librement pendant la séparation de phase. Pour une Tdis inférieure à Tcri, des membranes avec une structure bi-continue (cristallite forme alpha) sont obtenues. Ce domaine a été appelé "à grossissement empêché" dans la mesure où la séparation de phase s'accompagne d'une gélification. Nous avons démontré que la morphologie et le polymorphisme cristallin des membranes de PVDF peuvent ainsi être contrôlés par la Tdis et la vitesse d'échange avec le non-solvant. Ces résultats sont interprétés en termes d'auto germination et de compétition entre gélification, cristallisation et démixtion L-LThis dissertation shows how the morphology and polymorphism of poly(vinylidene fluoride) (PVDF) membranes prepared by using vapor-induced phase separation (VIPS) and liquid-induced phase separation (LIPS) were tuned by varying the dissolution temperature at which PVDF was dissolved (Tdis) to form the casting solution. We observed a transition temperature denoted by critical dissolution temperature, Tcri, across which the morphology and polymorphism of membranes (obtained by VIPS) drastically changed. The phenomenon was considered as general, as a Tcri was observed for all the three solvents N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc), and N,N-dimethylformamide (DMF) and the non-solvents, water and a series of alcohols, used in the present study. No matter which Tdis we used, polymer crystallization occurred prior to the L-L demixing. With Tdis above Tcri, the prepared membranes were composed of nodules (mainly in beta crystalline form) and the size of polymer domains decreased as the Tdis decreased. Because the polymer chains could freely coarsen to a large domain during the phase separation, we called the system free coarsening. With Tdis below Tcri, membranes with lacy (bi-continuous) structure (mainly in alpha crystalline form) were obtained. Because the polymer solution gelled during the phase separation, we called the system hindered coarsening. It was proven that PVDF membrane morphology and crystalline polymorphs can be monitored by Tdis and the solvent-nonsolvent exchange rate. These results were discussed in terms of self-seeding effect and competition between the gelation, crystallisation and L-L demixing
25
Kim, Jae-Kyung. "Preparation of Porous Polymeric Materials by Phase Separation Induced in the Course of Drying a Ternary Polymer Blend Solution." 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/124504.
Full text
26
Erikson, Pontus. "The Interaction of Oil and Polymer in the Microporous Polyethylene Film when using a Thermally Induced Phase Separation Process." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-266155.
Full textAbstract:
The battery separator is a component of the conventional battery that for long has been overlooked. Just because it’s the only inactive component, doesn’t mean it’s any less important for the battery cell. Recent trends point to an immense growth of the electrical vehicle-industry, and by so, also the lithium-ion battery separators market. This is because the lithium-ion battery is the most common battery type in commercial electrical vehicles. In one of the major manufacturing processes of the separator, mineral oil is used, to achieve a porous film. This study aims to evaluate different oils interaction with the polymer resin in the manufacturing process. Since most oils used in the battery separator industry today use paraffin rich oils, oils with different naphthenic content is tested to find correlations between the oils properties and the crystallinity or the porosity. No correlations for either the porosity or the crystallinity could be made to the oil’s properties. The images taken with the SEM was not enhanced enough to study the pores themselves or the pore structure of the films. For future studies it is recommended to collect more data to identify outliers so more accurate values are obtained. The methodology needs to be verified to ensure the procedure is reproducible. For the study of the pores and the pore structure, an FE-SEM should be used to achieve greater quality enhancement images on the surface of the films.Batteri separatorn är en komponent i det konventionella batteriet som länge har förbisetts. Bara för att den är en inaktiv komponent, betyder inte att den är mindre viktig för battericellens prestation. Trender idag pekar mot en enorm tillväxt inom elbils-industrin, och med det även litium-jon batteriseparatorns marknad. Det är för att litium-jon batteriet är det batteriet som vanligen används kommersiellt idag i elbilar. I en av de två stora industriella tillverkningsprocesserna används olja för att åstadkomma en porös film. Denna studie syftar på att utvärdera olika oljors interaktion med polymeren i denna tillverkningsprocess. Eftersom de flesta batteriseparator-industrier idag använder paraffinrik olja så testas oljor med olika mycket naftalensikt innehåll för att hitta korrelationer mellan oljornas egenskaper och kristalliniteten eller porositeten hos filmerna. Inga korrelationer för porositeten eller kristalliniteten kunde göras till oljornas egenskaper. Bilderna tagna med SEM var ej tillräckligt förstorade för att kunna studera vare sig porstorleken eller porstrukturen hos filmerna. För framtida studier rekommenderas att samla in mer data för att kunna utskilja ”outliers” i datan, för att erhålla mer korrekta värden. Metodiken måste även verifieras för att säkerställa att proceduren är reproducerbar. För att studera porerna och porstrukturen, borde en FE-SEM användas för att få mer förstorade bilder med bättre kvalité på filmernas yta.
27
VITRANO, Ilenia. "USO DI TECNICHE AVANZATE PER LA OTTIMIZZAZIONE STRUTTURALE E FUNZIONALE DI SCAFFOLD COMPOSITI POLIMERO-CARICA INORGANICA PER LA RIGENERAZIONE OSSEA." Doctoral thesis, Università degli Studi di Palermo, 2020. http://hdl.handle.net/10447/395408.
Full text
28
Wenning, Christian [Verfasser], Annette M. [Gutachter] Schmidt, and Marc C. [Gutachter] Leimenstoll. "Reaction-Induced Phase Separation of PPG/PEO/HDI based bi-Soft Segment Polyurethanes / Christian Wenning ; Gutachter: Annette M. Schmidt, Marc C. Leimenstoll." Köln : Universitäts- und Stadtbibliothek Köln, 2017. http://d-nb.info/1151638307/34.
Full text
29
Hanafia, Amira. "Étude des mécanismes interdépendants d’élaboration d’une membrane polymère sans solvant organique par une méthode originale de séparation de phase (TIPS-LCST), à partir d’un polymère biosourcé : l’hydroxypropylcellulose." Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20045.
Full textAbstract:
La séparation de phase au sein d'un système polymère/solvant est la méthode la plus couramment utilisée pour élaborer une membrane polymère poreuse. Les principales méthodes d'inversion de phase nécessitent l'usage de solvants organiques qui génèrent des problèmes environnementaux (traitement des bains de coagulation) et sanitaires (sécurité des installations industrielles). Cette étude porte sur le développement d'une nouvelle membrane polymère poreuse à partir d'un polymère biosourcé et hydrosoluble, l'hydroxypropylcellulose (HPC), permettant de s'affranchir de l'usage de solvants organiques. La propriété de thermosensibilité de l'HPC, caractérisé par une température critique basse en solution dans l'eau (LCST) de l'ordre de 40 °C, a par ailleurs permis de développer un procédé original d'élaboration de membranes HPC par séparation de phase induite par augmentation de la température au-delà de la LCST. Ce travail vise un triple objectif : (i) déterminer la formulation idoine permettant de former une membrane poreuse insoluble dans l'eau à partir d'HPC, (ii) appréhender et comprendre les mécanismes de structuration de la matrice polymère à travers l'interaction des mécanismes interdépendants de séparation de phase par décomposition spinodale, de réticulation chimique et d'extraction du solvant par évaporation et enfin (iii) caractériser l'aptitude des membranes à la filtration d'une solution aqueuse sous pression. Le suivi en ligne de la dynamique de séparation de phase d'un système HPC/eau/réticulant ± porogène (PEG200) par microscopie optique en contraste de phase, de la réticulation par rhéologie et de l'évaporation de l'eau par thermogravimétrie a ainsi permis de mettre en évidence l'impact de la formulation et des paramètres de conduite du procédé d'inversion de phase sur les propriétés morphologiques et d'usage des membranes. La porosité membranaire et le caractère symétrique de la morphologie ont notamment été corrélés à la vitesse des phénomènes concomitants de réticulation et d'évaporation de l'eau, donc à la vitesse de montée en température du procédé TIPS-LCST. La caractérisation de la perméabilité à l'eau des membranes HPC a confirmé l'efficacité de la réticulation et la résistance structurale des membranes au cours de plusieurs filtrations continues à l'eau. En raison du caractère thermosensible de l'HPC, ces membranes ont montré une aptitude remarquable à la filtration de solutions aqueuses à température élevée (60 °C). Par ailleurs, il a été montré que la perméabilité des membranes pouvait être en partie contrôlée par la température et la pression transmembranaire appliquéePhase separation of polyer/solvent system is the most widespread industrial process to manufacture membranes. Large solvent quantity is usually used whatever the process, hence leading to environmental (coagulation and washing baths treatment) and health (industrial and plant safety) problems.This study focuses on the development of new porous membranes made from hydroxypropylcellulose (HPC), a water soluble polymer, avoiding the use of any organic solvent. Moreover, the thermo-sensitive character of this polymer, characterized by a Lower Critical Solution Temperature (LCST) in water of about 40 °C, enabled to design an original thermally induced phase separation process by temperature increase above the LCST. This study aims (i) to find the ideal polymer solution composition to produce insoluble HPC membrane, (ii) to approach and understand the link between phase separation mechanism by spinodal decomposition, crosslinkig reaction and water extraction by evaporation, (iii) characterize pure water permeability under pressure. On-line monitoring of phase sepration dynamics by phase contrast optical microscopy, crosslinking reaction by rheology and water evaporation by thermogravimetric analysis of the system HPC/water/cross-linking agent ± porogen (PEG200) allowed an understanding of simultaneous and related mechanisms occurring during elaboration (phase separation / cross-linking / water evaporation) and a correlation with HPC membrane morphologies and characteristics in relation with phase separation process parametres. Pure water permeability characterization demonstrated the efficiency of cross-linking and structural strength during several filtration cycles. Furthermore, it has been shown that water permeability of HPC membranes could be controlled in part by the temperature and the applied pressure
30
Yen, Chi. "Synthesis and Surface Modification of Nanoporous Poly(ε-caprolactone) Membrane for Biomedical Applications." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1268074499.
Full text
31
Jiang, Wen. "Zwitterionic Separation Materials for Liquid Chromatography and Capillary Electrophoresis : Synthesis, Characterization and Application for Inorganic Ion and Biomolecule Separations." Doctoral thesis, Umeå : Univ, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-153.
Full text
32
Nkabyo, Henry Ane. "A study on the reversible photo-induced isomerisation of platinum(II) and palladium(II) complexes of the N,N-dialkyl-N’-acyl(aroyl)thioureas with reversed-phase HPLC separation from related rhodium(III), ruthenium(III) and iridium(III) complexes." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86773.
Full text
33
Lima, Juliana Aristeia de. "Comportamento de fases de soluções binarias e ternarias de poli(etileno-co-alcool vinilico), poli(metacrilato de metila) e dimetilformamida." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248789.
Full textAbstract:
Orientador: Maria Isabel FelisbertiTese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
Made available in DSpace on 2018-08-12T12:37:28Z (GMT). No. of bitstreams: 1 Lima_JulianaAristeiade_D.pdf: 4425741 bytes, checksum: e0c47d6335f66cc31a0fe6e5ac1c0457 (MD5) Previous issue date: 2008
Resumo: Neste trabalho foram estudadas blendas de poli(etileno-co-álcool vinílico) (EVOH), um copolímero semicristalino que combina segmentos hidrofílicos e hidrofóbicos e poli(metacrilato de metila) (PMMA), um polímero amorfo e hidrofílico. As blendas de EVOH, com teor de etileno variando de 27 a 44 mol %, e PMMA foram preparadas por casting a partir de soluções em DMF, e por mistura mecânica em um mini-misturador, objetivando: i) avaliar o comportamento de fases e a morfologia das blendas, EVOH/PMMA, em função da composição das misturas, do teor de etileno nos copolímeros de EVOH e do método de preparação; ii) obter os diagramas de fases das soluções binárias, EVOH/DMF, e ternárias, EVOH/PMMA/DMF, através do processo de separação de fases induzido termicamente (TIPS). O comportamento de fases das blendas, EVOH/PMMA, foi estudado através de Calorimetria Diferencial de Varredura (DSC) e Análise Dinâmico-Mecânica (DMA). A morfologia das blendas foi investigada por Microscopia Eletrônica de Varredura (SEM). As blendas independentemente do modo de preparação e da composição são imiscíveis. Como conseqüência desta imiscibilidade, as temperaturas de fusão (Tf) e cristalização (Tc) não são afetadas pela presença de PMMA. A morfologia das blendas varia com a composição e método de preparação. As blendas obtidas pelo método mecânico são compactas, apresentando morfologia de fase dispersa em uma matriz, com inversão de fases em aproximadamente 50 % em massa de cada componente. As soluções binárias, EVOH/DMF, e ternárias, EVOH/PMMA/DMF, foram submetidas a ensaios para a determinação das temperaturas de turvamento (Tturv) por microscopia ótica, e de cristalização dinâmica (Tcd), por DSC. As soluções binárias apresentaram comportamento UCST (upper critical solution temperature), sendo que a separação de fases L-L ocorre a temperaturas superiores à separação de fases S-L. O modelo de interações binárias prevê que a curva de separação L-L para as soluções EVOH- 38/DMF esteja situada a temperaturas superiores em relação às soluções EVOH-32/DMF e indica que a separação de fases resulta da baixa afinidade entre segmentos hidrofóbicos do EVOH com os segmentos do polímero contendo hidroxila e com o solvente, DMF, concordando com os dados obtidos experimentalmente. Filmes de EVOH obtidos pela evaporação do solvente mostraram-se densos, sem a presença de poros. As soluções ternárias também apresentaram comportamento UCST, resultando em duas fases macroscópicas, F1 e F2, à temperatura ambiente. A composição destas fases foi determinada por Análise Termogravimétrica (TGA), e os resultados mostraram que uma das fases macroscópicas é rica em EVOH e outra fase é rica em PMMA. As blendas resultantes da secagem dos sistemas ternários apresentaram duas camadas: uma densa e rica em PMMA e outra porosa e rica em EVOH. A presença de PMMA foi decisiva à formação de estruturas porosas
Abstract: In this work blends of poly (ethylene-co-vinyl alcohol) (EVOH), a semicrystalline copolymer which combines hydrophobic and hydrophilic segments and poly (methyl methacrylate) (PMMA), an amorphous and hydrophilic polymer were studied. EVOH blends, with ethylene content ranging from 27 to 44 mol% and PMMA were prepared by casting from solutions in DMF, and by mixing into a mini-mixer, with the objective of: i) evaluate the phase behavior and the morphology of the blends, EVOH/PMMA, depending on the composition of mixtures, the ethylene contents in the copolymers of EVOH and the conditions of mixing; ii) obtain the phase diagrams of the binary and ternary solutions, EVOH/DMF and EVOH/PMMA/DMF, respectively, by the process of thermally induced phase separation (TIPS). The phase behavior of the blends, EVOH / PMMA, was investigated by Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). The morphology of the blends was investigated by Scanning Electron Microscopy (SEM). The blends independently of the method of preparation and of the composition are immiscible. As a result of immiscibility, the melting temperature (Tm) and the crystallization temperature (Tc) are not affected by the presence of PMMA. The morphology of the blends varies with the composition and with the method of preparation. The blends produced by the mechanical method is compact, showing morphology of dispersed phase in a matrix, with inversion of phases in about 50% by weight of each component. The binary solutions, EVOH-38/DMF and EVOH-32/DMF, were submitted to experiments to determine the cloud temperature (Tcloud) by optical microscopy, and the dynamic crystallization (Tcd), by DSC. The binary solutions show UCST behavior (upper critical solution temperature), and the L-L phase separation occurs at higher temperatures than the S-L phase separation. The binary interaction model provides the L-L line to the EVOH-38/DMF, solutions which was situated at higher temperatures than the EVOH-32/DMF solutions and indicates that the phase separation results from the low affinity between the hydrophobic segments of EVOH with the segments of the polymer containing hydroxyl and the solvent, DMF, which agrees with the data obtained experimentally. Films of EVOH obtained by the solvent evaporating seemed to be dense, without the presence of pores. The ternary solutions also had UCST behavior, resulting in two macroscopic phases, F1 and F2, at room temperature. The phase compositions were determined by Thermogravimetric Analysis (TGA), and the results showed that one of the macroscopic phases is rich in EVOH and the other phase is rich in PMMA. The blends resulting from drying of ternary systems had two layers: a dense and rich in PMMA and another porous and rich in EVOH. The presence of PMMA was crucial to the formation of porous structures
Doutorado
Físico-Química
Doutor em Ciências
34
Mourier, Élise. "Nano-structuration sous contraintes de polyuréthanes segmentés thermoplastiques." Thesis, Lyon 1, 2009. http://www.theses.fr/2009LYO10267.
Full textAbstract:
Les polyuréthanes segmentés thermoplastiques (TPUs) sont des matériaux élastomères thermoplastiques qui couvrent une large gamme d’applications. Ces matériaux possèdent intrinsèquement une aptitude à la nano-structuration car ils présentent dans leur structure macromoléculaire une alternance de segments rigides et de segments souples thermodynamiquement immiscibles en dessous d’une certaine température (température de micro-mélange). Ainsi, en refroidissant à partir de l’état fondu, une micro-séparation de phase, dont la cinétique dépend de la température, se produit. De plus, l’application d’une déformation avant cette structuration modifie sa cinétique. Ainsi, en vue d’appréhender l’effet de la mise en oeuvre sur certaines propriétés de ces matériaux, il s’avère intéressant d’étudier l’influence de l’histoire thermomécanique sur la structuration. Cette étude repose sur l’observation du comportement de cristallisation et/ou de séparation de phase de cinq polyuréthanes commerciaux de nature chimique différente, en fonction de différentes conditions thermiques et mécaniques appliquées en milieu modèle ou en conditions de mise en oeuvre réelles. Les techniques utilisées sont principalement rhéologiques, rhéo-optiques et par diffusion de rayons X aux petits angles (SAXS). Ces différentes analyses permettent d’affirmer que les contraintes appliquées dans le fondu des matériaux avant leur solidification modifient de façon drastique la cinétique de structuration mais aussi leur morphologie résultante. En effet, une orientation particulière des entités structurées au sein des matériaux peut être engendrée par des contraintes appliquées en fonction de leur intensité. Cette morphologie résultante particulière joue également un rôle sur les propriétés mécaniques finales des matériauxThermoplastic segmented polyurethanes are an important class of thermoplastic elastomers which cover a wide range of applications. These materials are multi-block copolymers composed of alternating “hard” and “soft” segments which are respectively below and above their glass transition temperature under ambient conditions. TPUs exhibit a twophase microstructure which arises from the thermodynamic incompatibility between the hard and soft segments. This microphase separation is often combined with the crystallization of either or both segments. The mechanical properties of these polymers will depend upon the overall multiblock length and the hard block sequence length and how they affect the material morphology. Our goal is to understand how the polyurethane final properties can be affected by the processing stresses (extrusion, injection…). In this scope, experiments were performed using a rheometer or an optical microscope coupled with a shearing hot stage. A preshear controlled treatment was applied and its effect on the material structuration was followed. These characterizations highlighted the enhancement of phase separation kinetics by the shear. For instance, for presheared samples, phase separation and/or crystallization of the hard segments occur ten times faster than for non-sheared ones. Moreover, SAXS experiments carried out on samples structured from several conditions illustrated perpendicular arrangements of crystalline domains perpendicularly to the flow direction. Finally, this particular morphology induced by shear modifies the materials final mechanical properties
35
Pierrot, François. "Polymérisation in-situ en milieu fondu et sous écoulement élongationnel pour l'élaboration de nouveaux matériaux." Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAE011/document.
Full textAbstract:
Dans ce travail de thèse, des mélanges réactifs de polymères thermoplastiques immiscibles PMMA,PE et PS ont été réalisés dans un mélangeur (RMX®) qui génère principalement des écoulements élongationnels connus pour leurs pouvoirs distributifs et dispersifs même lorsque les composants ont une différence de viscosité importante. La polymérisation in-situ du styrène a été conduite par auto-polymérisation thermique et grâce à des amorceurs radicalaires. Différentes méthodes de préparations et paramètres de mélanges ont été testés puis évalués par l’analyse d’images de microscopie électronique. Les plus petits nodules de PS que nous avons obtenus ont un rayon moyen de l’ordre de 50 nm. Des mélanges binaires 90/10 à base de PS ou PE et d’un thermodur polyépoxyde (MDEA/DGEBA) ont également été réalisés. Les nodules sphériques les plus petits que nous avons obtenus ont un rayon moyen de l’ordre de 65 nmIn this work, binary and ternary reactive blends based on immiscible thermoplastic polymers PMMA,PE and PS were realized. The in-situ polymerization of the styrene, precursor of PS, was led by thermal self-polymerization or still thanks to radical initiator. Blends were realized in a mixer named RMX who generates mainly extensional flows known for their distributive and dispersive skill even if components have an important viscosity difference. Various methods of preparation and parameters of mixtures were tested. Morphology was evaluated by the analysis of electronic microscopy images.The average radiuses of the dispersed PS phase were compared with those observed in the literature. The smallest that we obtained have an average radius of 50 nm. Binary mixtures 90/10 %m with PS or PE and with a thermodur polyepoxide (MDEA/DGEBA) were also realized. The smallest spherical nodules that we obtained have an average radius of the order of 65 nm
36
Akbarzadeh, Rosa. "Developing Hierarchical Polymeric Scaffolds for Bone Tissue Engineering." Miami University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=miami1376962498.
Full text
37
Arnett, Natalie Yolanda. "Synthesis and Characterization of Disulfonated Poly(Arylene Ether Sulfone) Random Copolymers as Multipurpose Membranes for Reverse Osmosis and Fuel Cell Applications." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/26662.
Full textAbstract:
The results described in this dissertation focus on the synthesis and utilization of several disulfonated poly(arylene ether) random copolymer membranes in fuel cell and reverse osmosis applications. Poly(arylene ether)s were prepared by direct step copolymerization using a third monomer 3,3–-disulfonated 4,4–-dichlorodiphenylsulfone. The membrane properties of a 4,4–-biphenol-based disulfonated poly (arylene ether sulfone) random copolymer (BPS-35), optionally blended with various fluorine containing polymers or unsulfonated biphenol-based poly (arylene ether sulfone)s (Radel R) were investigated for fuel cell applications. Fluorine containing copolymers used included with 2,2–-hexafluoroisopropylidene 4,4–-biphenol based unsulfonated (6F-00) or disulfonated (6FS-35 and 6FS-60) PAES, hexafluoroisopropylidene biphenol based 4,4–-difluoro phenyl phosphine oxide) (6FPPO), and poly(vinylidene fluoride) (Kynar®). Tapping mode atomic force microscopy (TM-AFM) images of the membranes with 10 wt% of fluorinated copolymers showed macroscopic phase separation. Good miscibility between the copolymers at low concentrations was also confirmed by the observation of only one glass transition temperature. Compared to the benchmark Nafion 1135, the 10wt% blends of the fluorinated copolymers afforded a considerable reduction in the methanol permeabilities, which is important for direct methanol fuel cells (DMFC). The best DMFC performance with 0.5 M methanol fuel was illustrated with blends containing 10 wt% 6FS-00. At higher methanol concentrations (up to 2.0 M) BPS-35/6FS-00 (90/10) membranes outperformed both Nafion membranes.
Blends of BPS-35 blends with 6FS-35 or Radel R were also used as RO membranes. The highest salt rejections of 97.2 and 98.0% were obtained from BPS35/Radel R (90:10) and BPS-35/6FS-35 (95:5) blends, respectively in the salt form.
A systematic study of the preparation of BPS-20 random copolymer skin-core asymmetric membranes by diffusion induced phase separation (DIPS) from various polar aprotic solvent or cosolvent systems is reported. The best aprotic solvents to generate an asymmetric structure were NMP and DMAc whereas tetrahydrofuran (THF)/ formamide (FAm) (80/20 v/v) mixtures proved to be the best co-solvent systems. Acetone was the best non-solvent to prepare asymmetric membranes from both aprotic solvents and co-solvent mixtures. Overall, asymmetric membranes prepared from THF/FAm co-solvent mixtures illustrated the most stable phase separated morphology that was free of macrovoids. However, thicker skins (~5 μM) were formed due to the high volatility of THF. Therefore, ultra-thin skin thin film composites (TFC) based on BPS-20 in diethylene glycol (Di(EG) were prepared. Thermal treatment of these TFC was conducted at 90 °C and the addition of 20 wt% glycerin to the casting formulation helped to prevent pore collapse in the porous Udel polysulfone. A minimum of three coats was required to obtain a dense, smooth, and pinhole free skin layer. The generation of three dimensional (ternary) solubility parameter phase diagrams based on experimental data was formulated and a region of solubility based on the solubility parameters of the aprotic solvents and the different co-solvent systems was established for BPS-20.Ph. D.
38
Michon, Marie-Laure. "Heterogeneous epoxy-amine networks from the dispersion of cross-linked polymer microparticles." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0018/document.
Full textAbstract:
Lors de cette étude, il a été étudié l'influence de l'ajout de microparticules de polymère réticulé (CPM) dans des formulations d'époxy-amine, sur la cinétique, la morphologie et les propriétés thermo-mécaniques des réseaux finaux obtenus. Tout d'abord, un protocole simple, robuste et bien contrôlé a été développé afin d’ obtenir une large gamme de taille de CPM, de Tg et de fonctionnalité amine. Ce protocole de polymérisation par précipitation, basé sur les phénomènes de séparation de phases, a également été appliqué à différentes compositions chimiques et différents monomères époxy hydrosolubles, ceci montrant les grandes possibilités de cette méthode. Une bonne interface entre les CPMs et la matrice a été recherchée en synthétisant les CPMs en excès de groupes amines. La quantification de ces groupes amines réactifs sur les CPMS était d'un grand intérêt et a donc été étudiée en profondeur. Le titrage des amines de surface a été réalisé en mettant au point un nouveau protocole qui a permis la quantification des amines primaires et secondaires sur les CPMs. Il a ensuite été mis en évidence que, bien que ces microparticules réticulées ne soient pas poreuses, des fonctions amines sont disponibles au cœur des particules et peuvent réagir avec d'autres molécules qui sont capables de diffuser dans la CPM. Il a été montré que lorsque les CPM ont été dispersées dans des mélanges d'époxy- amine, la diffusion des monomères dans le cœur de la CPM s'est produite mais différemment selon le procédé de dispersion. En effet, en utilisant le tétrahydrofurane comme solvant pour aider à la dispersion, la diffusion de la DGEBA est amplifiée et modifie les propriétés thermo-mécaniques du réseau final en modifiant le rapport stœchiométrique de la matrice. Le même phénomène a été observé mais moins amplifié lorsque les microparticules sont uniquement dispersées mécaniquement. En dispersant les CPMs dans l'amine qui est l'agent réticulant, on observe l'absorption complète de l'amine au coeur des CPMs, conduisant ainsi à la désorption de celle-ci dans une deuxième étape, permettant de créer le réseau. Ainsi, un comportement très complexe des CPM a été mis en évidence en présence des monomères et/ou solvant : le gonflement et les phénomènes de diffusion qui dépendent d'un certain nombre de paramètres tels que la température, la densité de réticulation des CPM, les paramètres de solubilité, etc. L'intensité du phénomène de diffusion conduit à une variété de comportements lorsque les CPMs sont ajoutées dans une formulation d'époxy-amine tels que: (a) une légère diminution du temps de gélification et l'augmentation de la conversion, (b) la modification de la température de transition vitreuse de la matriceThroughout this work, the influence of the addition of cross-linked polymer microparticles (CPMs) in epoxy-amine formulations on the kinetics, morphology and thermo-mechanical properties of the final networks have been investigated. First, an easy, robust and well-controlled protocol was developed to obtain a large range of CPM size, Tg and amine functionality. This protocol based on reaction induced phase separation via precipitation polymerization was also applied to different chemistries and water soluble epoxy pre-polymers showing the large possibilities of this method. The capacity of obtaining a good compatibility between the CPMs and the matrix was ensure by synthesizing the CPMs in excess of amino groups. The study of the remaining reactive amino groups on the CPMS was of great interest and therefore deeply investigated. The titration of the surface amine was performed by developing a new protocol that enabled the quantification of primary and secondary amines on CPMs. It was then highlighted that even though these cross-linked microparticles were not porous, amino groups are available into the core and can react with other molecules that are able to diffuse into the CPM core. It was shown that when CPMs were dispersed into epoxy-amine blends, the diffusion of monomers into the CPM core occurred but differently depending on the dispersion process. Indeed, using tetrahydrofuran as solvent to help for the dispersion increased the diffusion of DGEBA into the CPM core and changed the thermo-mechanical properties of the final network by modifying the stoichiometric ratio of the matrix. Same phenomenon was observed but less amplified when CPMs were mechanically dispersed in DGEBA. Regarding the dispersion of CPMs in the amine cross-linker, IPD, its complete absorption could be observed into the CPMs, leading then to the desorption of IPD to create the network. Thus, a very complex behavior of CPMs was highlighted in presence of monomers or/and solvent: swelling and diffusion phenomena that are dependent on a number of parameters such as temperature, CPM cross-link density, solubility parameters, etc. The intensity of those phenomena leads to a variety of behaviors when CPMs are added into an epoxy-amine formulation: (a) slight decrease of gel times and increase of conversion, (b) modification of glass transition temperature of the matrix
39
Klamser, Juliane Uta. "Transitions de phase en basse dimension à l’équilibre et hors d’équilibre." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS333.
Full textAbstract:
Bien que la nature soit tridimensionnelle, il existe de nombreux systèmes dont les dimensions effectives sont inférieures, offrant une nouvelle physique. Cette thèse porte sur les transitions de phase dans les systèmes de faibles dimensions, en particulier sur les phases hors équilibre dans la matière active (MA) bidimensionnelle (2D). À la différence des systèmes passifs, les particules actives sont entraînées par de l'énergie injectée à l'échelle microscopique à partir de degrés de liberté internes, entraînant une dynamique irréversible, et donnant souvent lieu à des phases macroscopiques contrastant avec l'équilibre. Dans une première partie, ce travail propose une caractérisation quantitative des phases hors équilibre en s'appuyant sur un modèle minimal de MA. Ce modèle repose sur des particules 2D autopropulsées avec des interactions de paires. La dynamique (Monte Carlo cinétique persistante) est une variante des disques passifs et diffère des modèles bien connus de MA. Un diagramme de phase quantitatif complet est présenté, incluant la séparation de phase induite par motilité (SPIM). De plus, le scénario de fusion en deux étapes avec la phase hexatique se retrouve aussi hors équilibre. L'activité peut fondre un solide 2D et les lignes de fusion restent séparées de SPIM. La deuxième partie explore l'existence de transitions de phase dans les modèles 1D classiques avec des interactions courtes portées à température non nulle. Une idée largement partagée est que de telles transitions sont impossibles. Un contre-exemple clair est présenté où la non-analyticité de l'énergie libre émerge d'un nouveau mécanisme d'origine géométrique, établi de manière rigoureuseAlthough nature is three-dimensional, lower dimensional systems are often effectively realized offering fascinating new physics. The subject of this thesis is phase transitions in low dimensions, with its primary focus on non-equilibrium phases in two-dimensional active matter. Unlike passive systems, active particles are driven by energy injected at the microscopic scale from internal degrees of freedom resulting in an irreversible dynamics, often giving rise to macroscopic phases in striking contrast to equilibrium. A goal is to give a quantitative characterization of such non-equilibrium phases and to capture these in simplest realizations of active matter. The thesis explores two-dimensional self-propelled particles with isotropic pair-wise interactions. The dynamics (persistent kinetic Monte Carlo) is a variant of passive disks and different from well-known models of active matter. A full quantitative phase diagram is presented including motility induced phase separation (MIPS) as seen in other active systems. Additionally, the famous two-step melting scenario with the hexatic phase extends far from equilibrium. In this non-equilibrium scenario, the activity can melt a 2D solid and the melting lines remain separated from MIPS. The second part explores a frequently debated issue of the existence of phase transitions in classical one-dimensional models with short-range interactions at non-zero temperature. A widely shared misconception is that such transitions are not possible. A clear counterexample to this belief is given where non-analyticity in the free energy emerges from a new mechanism with a geometrical origin, which is then established on a rigorous ground
40
Marques, Rosalva dos Santos. "Comportamento de fases de soluções de poliolefinas funcionalizadas e implicação na obtenção de membranas pelo processo TIPS." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248781.
Full textAbstract:
Orientador: Maria Isabel FelisbertiTese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
Made available in DSpace on 2018-08-26T22:37:44Z (GMT). No. of bitstreams: 1 Marques_RosalvadosSantos_D.pdf: 38406911 bytes, checksum: 574d251b2b2578b4a3d9fd0b4e82fcf7 (MD5) Previous issue date: 2014
Resumo: Neste trabalho, estudou-se o comportamento de fases de soluções binárias e ternárias de poliolefinas funcionalizadas com hidroxilas (EVOH) e ácido carboxílico (PEAA) nos solventes dimetilformamida e álcool benzílico. Utilizou-se EVOH contendo 27 e 44 mol % e PEAA contendo 80 mol % de etileno. As soluções exibem o comportamento de fases do tipo UCST, apresentando separações de fases líquido-líquido (L-L) e sólido-líquido (S-L). As temperaturas de separação de fases L-L e S-L, TL-L e TS-L, respectivamente, foram determinadas para soluções com diferentes composições por inspeção visual e por DSC, respectivamente. Enquanto TS-L para as soluções binárias de EVOH varia fortemente da com a composição das soluções binárias, TS-L para as soluções binárias de PEAA é praticamente constante. Estes resultados foram interpretados sob a ótica de um modelo em que a cristalização do PEAA, que envolve os segmentos de etileno do copolímero, ocorre quase na ausência de solvente. Já a cristalização do EVOH, que envolve os segmentos hidroxilados, ocorre em meio ao solvente, em uma condição em que o potencial químico do polímero varia com a composição da solução. Este modelo pode ser comprovado por estudos de fluorescência empregando-se o pireno e o acetato de uranila como sondas hidrofóbica e hidrofílica, respectivamente. Estes estudos de fluorescência permitiram também acessar transições não detectáveis por DSC. As soluções ternárias homogêneas apresentam mais de uma separação de fases L-L quando submetidas a resfriamento. O diagrama de fases ternário foi construído determinando-se as composições das soluções em equilíbrio, decorrentes da primeira separação de fases L-L, por termogravimetria de alta resolução. Os diagramas de fases das soluções ternárias resultantes das combinações possíveis entre os diferentes polímeros e solventes apresentam regiões de miscibilidade limitadas localizadas em regiões próximas aos vértices, sendo as composições das fases em equilíbrio características de cada combinação nas soluções ternárias. Os materiais resultantes da evaporação do solvente de soluções submetidas ao processo TIPS (Temperature Induced Phase Separation) são compactos ou porosos, dependendo da afinidade polímero-solvente. Entretanto, as morfologias dos materiais resultantes de soluções ternárias submetidas ao processo TIPS são únicas e características do par polímero-polímero, demonstrando que a estratégia de combinação de polímeros para controlar a morfologia é viável
Abstract: The phase behavior of binary and ternary solutions of functionalized poliolefins with hydroxyls (EVOH) and carboxylic acid (PEAA) were studied using dimethylformamide and benzyl alcohol as solvents. PEAA containing 80 mol % and EVOH containing 27 and 44 mol % of ethylene were used. The binary and ternary solutions present a typical UCST behavior associated to liquid-liquid (L-L) and solid-liquid (S-L) phase separation. The temperatures related to L-L and S-L phase separation, TL-L e TS-L, respectively, were determined visually and using DSC, respectively. While TS-L depends on the EVOH solution composition, it is practically constant for PEAA solutions. These results were explained using a model in which the crystallization of PEAA from the solution occurs in absence of solvent, once it involves the polyethylene segments. On the contrary, the crystallization of EVOH from the solution, that involves the hydroxylated segments, occurs in presence of the solvent. This condition leads to the decrease of the chemical potential of EVOH in the solution. The models could be proved by fluorescence experiments using pyrene and uranyl acetate as hydrophobic and hydrophilic probes, respectively. Moreover, the fluorescence experiments allow accessing other transitions not detectable by DSC for ternary solutions. The homogeneous ternary solutions present more than one L-L phase separation by cooling. The ternary diagram was determined by the first L-L phase separation using the composition data accessed by high resolution thermogravimetry. The ternary solutions of all possible combination of polymers and solvents show a restricted miscibility window in the regions near the vertices. The composition of the phases in equilibrium is characteristic of each ternary solution, as well as, the morphology of the materials resulting from the evaporation of the solvent after the solution being subjected to TIPS (Temperature Induced Phase Separation) process. This process applied to binary and ternary solutions resulted in dense or porous materials depending on the polymer-solvent affinity. However, the morphology resulting from ternary solutions subjected to TIPS process and solvent evaporation is unique, showing that the strategy of combining different polymers is a viable route to control the morphology of polymers
Doutorado
Físico-Química
Doutora em Ciências
41
Ly, Hai Bang. "Matériaux polymères fonctionnalisés à double porosité : conception et modélisation." Thesis, Paris Est, 2015. http://www.theses.fr/2015PESC1144/document.
Full textAbstract:
Les matériaux polymères poreux font l'objet d'intenses recherches depuis de nombreuses années et présentent certains avantages importants par rapport à leurs homologues inorganiques, comme des propriétés mécaniques modulables, une fonctionnalisation aisée et surtout un coût de production plus faible. Au cours de la dernière décennie, les matériaux à double porosité ont attiré une attention particulière de la communauté scientifique car ces matériaux offrent de nouvelles perspectives intéressantes pour l'élaboration de matériaux durables. Le rôle de chaque niveau de porosité est différent et associé à des processus de transfert de masse distincts. Les macropores (~ 100 µm) permettraient l'écoulement de macromolécules ou de cellules à travers le matériau, tandis qu'un réseau nanoporeux (10-100 nm) serait dédié au passage de molécules plus petites, agissant ainsi comme un deuxième mécanisme de transport, en particulier lorsque des macropores sont totalement obstrués. La première partie de ce travail porte sur le développement d'approches polyvalentes et efficaces pour la préparation de matériaux à double porosité biocompatibles à base de poly(méthacrylate de 2-hydroxyéthyle) (PHEMA). La première approche a reposé sur l'utilisation de deux types distincts de gabarits porogènes, à savoir un macroporogène et un nanoporogène. Pour générer la macroporosité, soit des particules de NaCl ou des billes de PMMA, pouvant être fusionnées ou non, ont été utilisées afin de contrôler la morphologie l'interconnectivité des pores. Le nanoporosité a été obtenue en utilisant diverses quantités de différents solvants porogènes, générant ainsi une large gamme de distributions de tailles de pores pour ce second niveau de porosité. La seconde méthodologie a été fondée sur le procédé de séparation de phases induite thermiquement. Un mélange de co-solvants constitué de dioxane et d'eau a été utilisé pour solubiliser le PHEMA linéaire préalablement préparé, suivi par un processus de solidification par congélation du mélange de co-solvants / PHEMA, et sublimation consécutive des co-solvants pour produire les matériaux de PHEMA biporeux correspondants. Enfin, les matériaux à double porosité ont été valorisés à travers différentes réactions de fonctionnalisation en utilisant la chimie du carbonyldiimidazole, et l'immobilisation postérieure de nanoparticules d'or générées in-situ. De tels matériaux hybrides à double porosité se sont avérés être des supports catalytiques efficaces.Dans la deuxième partie, nous avons déterminé numériquement la perméabilité des matériaux à double porosité. La méthodologie a été fondée sur une approche à double changement d'échelle dans le cadre des théories d'homogénéisation périodique et sur des calculs de cellules élémentaires. Le premier changement d'échelle a consisté à déterminer une première perméabilité associée au réseau de nanopores. A cette échelle, les pores ont été saturés par un fluide visqueux obéissant aux équations de Stokes et le problème a été résolu par une approche classiques d'éléments finis ou en utilisant des techniques plus récentes à base de la transformée de Fourier rapide. À l'échelle mésoscopique, l'écoulement du fluide a obéi aux équations de Stokes dans les macropores et aux équations de Darcy dans le solide perméable. Le problème de cellules élémentaires couplant les équations de Darcy et Stokes a été résolu par la méthode des éléments finis afin de calculer la perméabilité macroscopique finale. Dans cette optique, nous avons développé une méthode fondée sur une formulation variationnelle mixte qui a été mise en œuvre en prenant différents éléments dans les domaines de solide et fluide. Divers exemples 2D et 3D sont fournis pour illustrer la précision et la capacité des méthodes numériques proposées pour calculer la perméabilité macroscopique des matériaux biporeuxPolymer-based porous materials have been the subject of intense research for many years and present some important advantages over their inorganic counterparts, such as tunable mechanical properties, ease to be functionalized, and especially lower production cost. Over the last decade, materials with dual porosity have attracted a particular attention from the scientific community, as these peculiar materials offer new interesting perspectives for engineering sustainable materials. The role of each porosity level is different and associated with distinct mass transfer processes. Macropores (~100 µm) would allow macromolecules and cells flow through the material, while a nanoporous network (10-100 nm) would be dedicated to the passage of smaller molecules, thus acting as a second transport mechanism, especially when macropores are totally clogged. The first part of this work addresses the development of versatile and effective approaches to biocompatible doubly porous poly(2-hydroxyethyl methacrylate) (PHEMA)-based materials. The first approach relied on the use of two distinct types of porogen templates, i.e. a macroporogen and a nanoporogen. To generate the macroporosity, either NaCl particles or PMMA beads that could be fused or not, were used in order to control the pore morphology and interconnectivity of the materials. The nanoporosity was obtained by using various amounts of different porogenic solvents, thus generating a wide range of pore size distributions for this second porosity level. The second methodology was based on the thermally-induced phase separation process. A co-solvent mixture constituted of dioxane and water was used to solubilize previously prepared linear PHEMA, followed by a solidification process by freezing the co-solvents/PHEMA mixture, and subsequent sublimation of the co-solvents to generate the corresponding biporous PHEMA materials. Finally, advantage of doubly porous materials was taken through different functionalization reactions using carbonyldiimidazole chemistry, and further immobilization of in-situ generated gold nanoparticles. Such hybrid doubly porous materials proved to act as efficient catalytic supports. In the second part, we numerically determined the permeability of doubly porous materials. The methodology was based on a double upscaling approach in the field of periodic homogenization theories and on unit cell calculations. The first upscaling consisted in the determination of a first permeability associated with the array of nanoscopic pores. At this scale, the pores were saturated by a viscous fluid obeying the Stokes equations and the problem was solved by means of standard Finite-Element approaches or using more recent techniques based on Fast Fourier Transform. At the mesoscopic scale, the fluid flow obeyed the Stokes equations in the macropores and the Darcy equations in the permeable solid. The unit cell problem coupling Darcy and Stokes equations was solved by the Finite Element method in order to compute the final macroscopic permeability. To this purpose, we developed a method based on a mixed variational formulation which was implemented by taking different elements in the solid and fluid regions. Various 2D and 3D examples were provided to illustrate the accuracy and the capacity of the proposed numerical methods to compute the macroscopic permeability of biporous materials
42
Pecher, Heike Susanne. "Entwicklung von Monolithen auf Basis polyfunktioneller Glycidylether für die Anwendung in der Affinitätschromatographie." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2014. http://dx.doi.org/10.18452/16933.
Full textAbstract:
Monolithische Phasen werden seit ca. 20 Jahren entwickelt und sind in den letzten Jahren eine attraktive Alternative zu etablierten mit Partikeln gefüllten Säulen geworden. Sie werden in anorganische Phasen und organische Polymermonolithe unterteilt. Monolithe bestehen aus einem einzigen, durchgehenden Stück. Charakteristisch ist das sie durchziehende Porennetzwerk, durch das der Eluent mit geringerem hydraulischen Widerstand fließen kann und das somit schnellere Flussraten ermöglicht. Polymermonolithe werden vorwiegend für die Separation großer Biomoleküle aufgrund eines durch Konvektion beschleunigten Massentransfers eingesetzt. Zudem sind sie über einen breiten pH-Wert-Bereich stabil und können direkt (in situ) im gewünschten Format polymerisiert werden. In der vorliegenden Arbeit gelang die Herstellung neuartiger epoxidbasierter Phasen nach einem von Weller et al. entwickelten Konzept, die im Affinitätsexperiment angewendet wurden. Die Herstellung erfolgte durch Autopolymerisation polyfunktioneller Glycidylether. Für die Funktionalisierung wurden nicht polymerisierte Epoxide genutzt. Als Monomere dienten TEPIC, GE 100 sowie GE 500. Die Arbeiten konzentrierten sich vor allem auf die bei Raumtemperatur durchführbaren Synthesen mit dem höher funktionellen GE 500. Die Polymerisationsbedingungen wurden hinsichtlich Porogenmischung und -anteil optimiert. Eine mit 75 Vol.-% Porogen (Dioxan/ MTBE (2:3)) hergestellte und mit rProtein A funktionalisierte Kapillarsäule (66 %, 12 µm, 7m2/g) ergab im Affinitätsexperiment eine Kapazität von 0,44 mg/mL aus Kaninchenserum isolierbarem IgG. Durch Beimischung von 60 % BDE konnte der Epoxidgehalt vervierfacht und die Porengröße auf 400 nm bei 59 % Porosität reduziert werden. Die spezifische Oberfläche wurde verdreifacht und die Kapazität präparierter Disks auf 0,90 mg/mL etwa verdoppelt. Die in dieser Arbeit entwickelten Disks können zur Isolierung von IgG aus einer komplexen Probe, wie beispielsweise Blutserum, eingesetzt werden.Monolithic supports have been developed since 20 years and have become an attractive alternative to well-established columns packed with particles over the past years. They are classified into inorganic media and organic polymer monoliths. Monoliths consist of a single, continuous piece with an integrated characteristic porous network through which the eluent can flow with lower hydraulic resistance and which consequently offers higher flow rates. Due to an accelerated mass transfer caused by convection polymer monoliths are mainly used for separation of large biomolecules. In addition, they are stable over a wide pH range and can be polymerized directly (in situ) in the desired format. In the present work the successful preparation of new epoxide-based supports according to a concept introduced by Weller et al. as well as their application in affinity chromatography are reported. Their preparation was carried out by self-polymerization of polyfunctional glycidyl ethers and for functionalization non-polymerized epoxide groups were used. As monomers TEPIC, GE 100 and GE 500 were utilized. The work has focused especially on the polymerization of the higher functional GE 500, which can be perfomed at room temperature and was optimized in terms of both composition and amount of porogen. The extraction of IgG from rabbit serum with a capillary column (66 %, 12 µm, 7m2/g) prepared by 75 vol.-% porogen (dioxane/ MTBE (2:3)) and functionalized with rprotein A resulted in a capacity of 0,44 mg/mL. By addition of 60 % BDE the epoxide content was quadrupled and the pore size reduced to 400 nm while maintaining consistently high porosity of 59 %. The specific surface area was tripled and the capacity of prepared disks approximately doubled to 0,90 mg/mL. The disks developed in this work can be applied for the isolation of IgG from complex samples such as serum.
43
Chiang, Wen-Pang, and 江文邦. "Preparation of Porous Membranes by Polymerization Induced Phase Separation： Control of Surface Morphology." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/65552294954528519853.
Full textAbstract:
碩士國立臺北科技大學
化學工程系碩士班
92
Membranes with porous structure were prepared by polymerization induced phase separation. The surface morphology of membranes can be tailored by choice of the various contact films. In this study the porous membranes were made of stepwise polymerization of a mixture of bisphenol-A epoxy resin（DER-331）, long chain polyglycol diepoxide resin（DER-732）, and curing agent, diethylenetriamine（DETA）, in various solvents, such as 2,6-dimethyl-4-heptanone, cyclohexanol, and cyclohexane. The surface morphology of membranes was observed by a SEM. In the SEM micrographs it is demonstrated that surface morphology of membranes can be tailored by the contact films. The pore size of the membrane surface increases with decreasing the wettability between the monomer solution and the contact films. However, it was found that in a lower wettability between monomer solution and contact film, the surface pore size of the membrane decreases. The porous morphology inside of membrane is controlled by the volume percentage of solvent. The pore size increases with increasing the amount of solvent. Furthermore, the porous membranes were made of photo-chemically initiated polymerization of a mixture of methacry acid（MAA）, ethylene glycol dimethacrylate（EDMA）, and tripropylene glycol diacrylate （TPGDA）in various solvents, such as toluene, and 2-butanol. The surface morphology of membranes was observed by a SEM. The morphology of the membrane can be also tailored by different contact films pressed on the casting solution. It was found that the diffusion coefficient of the caffeine in the membrane increases with the surface porosity, while the equilibrium of sorption capacity is controlled by the bulk porosity of membrane.
44
Jana, Rounak. "Polymerizable Porogen – Direct generation of internally functionalized porous polymers." Thesis, 2022. https://etd.iisc.ac.in/handle/2005/5839.
Full textAbstract:
Bicontinuous functional porous polymers are desirable in terms of pore accessibility, particularly for applications in templating, chromatographic separation, and catalysis. Bicontinuous morphologies can be obtained by block copolymer self-assembly only over a very narrow compositional window, which makes it synthetically challenging. On the other hand, polymerization induced phase separation (PIPS) methodology for generating bicontinuous porous structures, which was discovered several decades ago, is an easy strategy, but it does not permit precise control over the pore size, especially at smaller sizes. To achieve multiple objectives in a single step, Seo and Hillmyer ingeniously combined the concepts of PIPS and BCP self-assembly to generate crosslinked polymer matrices, wherein they introduced a covalent linkage between the pore-forming segment and the matrix, allowing microphase separation to occur at the nanoscale dimensions; thus generating nanoporous polymers. The bicontinuous pores were obtained because of kinetic trapping of the microphase-separated domains via in situ crosslinking.
The main objective of my thesis is to develop an alternate strategy using a polymerizable porogen, wherein a polymerizable Styryl unit is linked to the pore-forming PEG segment via a thermally labile linker, namely a urethane. Copolymerization of the polymerizable porogen (PolyPo) with a crosslinker, divinyl benzene (DVB), leads to the formation of a microphase separated crosslinked matrix; one of the defining ideas of the study is the exploitation of the thermal reversibility of the urethane linkage between the pore-forming segment and the matrix, which not only disconnects the porogen to generate the porous matrix but also leaves behind amine groups (upon reaction with water) that lines walls of the pore. Careful examination of the in situ microphase separation process during the copolymerization of the PolyPo, revealed that slowing down the polymerization by using controlled radical polymerization is essential to prevent premature crosslinking and allow effective microphase separation. The pore volume and surface area in these systems could be easily controlled by varying the ratio of porogen to the crosslinker, whereas the average pore size depended only on the length of the PEG porogenic segment. This concept was extended to the distyryl systems where both ends of the porogen PEG segment were linked to polymerizable groups; it was shown that the pore size was dependent only on the size of the porogenic segment and was unaffected by the presence of two polymerizable units. Further, it was shown that carrying out the copolymerization of the PolyPo in the presence of free PEG porogen could be an effective strategy for controlling the average pore dimension, despite broadening of the size distribution; likewise, copolymerization of two PolyPos carrying different PEG segments proved to be an alternate approach for fine-tuning the average pore size.
Finally, we showed that the pore-generating PEG segment could also be designed as a counter-ion to a suitable polymerizable unit; in this case PEG-trimethylammonium, 4-vinylbenzoate was designed as an ionic PolyPo. Here, a simple MeOH-HCl wash at 70°C was adequate for near-complete removal of the porogen PEG segment. The pore size, pore volume, and surface area of these counter ion-based systems varied much like their covalent counterparts. Most importantly, the porous crosslinked matrix that was generated using this approach carried carboxylic acid groups, unlike the earlier urethane-based strategy that left behind amine groups. In summary, we demonstrated novel single-step strategies for the preparation of crosslinked bicontinuous porous polymers carrying tailorable functional groups on the pore walls, with excellent control over the pore size and surface area.CSIR NET
45
Huang, Nan-Du, and 黃南都. "Study on Chemically Induced Phase Separation." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/888n7k.
Full textAbstract:
碩士國立臺北科技大學
化學工程所
93
Membranes with porous structure were formed by polymerization induced phase separation. In this study, the porous membranes were made of stepwise polymerization of a mixture of bisphenol-A epoxy resin (D.E.R. 331), polyglycol diepoxide resin (D.E.R. 732), and curing agent, diethylenetriamine (DETA), in different porogen. The surface morphology of membranes was observed by a SEM. It was found that the surface morphology of membrane is changed with the contact films. First, the pore size of the membrane surface increases with decreasing the wetting between the monomer solution and the contact films. However, the curing solution covered by a film with very low wet ability, such as Teflon, a dense skin or smaller pores formed during cure. The morphology of the membrane is also dependent on the ratio of D.E.R 732. The cloud-point profiles changed with the epoxy conversion at various temperatures were determined by a DSC and a microscope coupled with a UV-Vis spectrometer. The conversion of cloud-point increases with the curing temperature.
46
王偉弘. "Microporous Membrane Formation via Thermally Induced Phase Separation." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/01744743760511800226.
Full textAbstract:
碩士長庚大學
化學工程研究所
86
Thermally induced phase separation (TIPS) of polymer solutions is a commonly used technique to prepare microcellular foams or membranes with controlled morphologies. In this study, light scattering have been used to study morphology development in PC membrane formed by thermal inversion method. Cloud point was determined by transmittance and differential scanning calorimetry. Analysis of the early stage behavior of scattered intensity in terms of Cahn Hilliard theory established spinodal decomposition as the mechanism of phase separation for the conditions studied. Standard Cahn-Hilliard analysis predicts that the intensity at a given wavenumber should grow exponentially with time. For the same annealing time, the domain size increases with decreasing quench temperature. Consistent with our results, other light-scattering studies of polymer solution showed that the position of the initial intensity maximum increased as the quench temperature was decreased. However, the electron microscopy data of Song and Torkelson showed the reverse trend. All of the quenches reported in the study were to regions of phase diagram where the concentrated phase that formed was quite close to its glass transition temperature. As the phase separation temperature was lowered, the polymer-rich phase was expected to be closer to its glass transition temperature where the mobility would drastically lower. This decrease in mobility was believed to be the main factor thatθmax would not change in the later stage.
47
Chan, Hung-Yi, and 詹弘毅. "Producing metal foams by pressure-induced phase separation." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/05741917512158726661.
Full textAbstract:
碩士義守大學
材料科學與工程學系
89
The purpose of this study is to employ the technique of PIPS (pressure-induced phase separation) in foaming metallic alloys. The effects of the temperature of the molten metal, the gas pressure, and the various kinds of gases on the density and the microstructure of the solidified metal are investigated. The metal sample is loaded into a high-pressure furnace, which could be optionally made of stainless tube, hot press, or pressure vessel, and heated up to their solidus. In the meanwhile, either the pressurized carbon dioxide or hydrogen gas is purged into the high-pressure furnace. After the molten metal is hold at the designed pressure and temperature for one hour, the gas in the furnace is rapidly depressurized. Then, the alloy is quenched into in cold water to study the feasibility in the production of metal foam by the PIPS. It is presumed that the bubbles, created after depressurization, in the liquid molten stops growing within five seconds. It is found that extending the growing time leads to bubble’s merge and collapse and/or drainage, which results in the decrease of the density of the solidified alloys. When carbon dioxide is applied to Pb-Sn alloy at 180℃, the number and the size of the bubbles increases and the density of the solidified alloys decreases while the gas pressure increased from 100 to 300bar. It is presumed that the solubility of carbon dioxide in the molten alloys increases with gas pressure. However, the change of density, bubble size, and number of bubble with gas pressure at 190℃ is not significant as that found in 180℃. This temperature effect needs further study. From their microstructure observed in SEM, it is found that much of the bubbles is located in the Tin-rich phase. It is presumed that the interaction between carbon dioxide and Tin is much stronger than that of Lead. When hydrogen is applied to Pb-Sn alloy at 205 and 210℃, the density of the solidified alloys is not affected by the gas pressure in the range of 2 to 10bar, and no significant bubbles is observed in their microstructure. It is presumed that the solubility of hydrogen gas in this pressure range is too low to create significant number of gas bubbles in the molten metal. This is confirmed by replacing Pb-Sn alloy by Zinc alloy, which also shows that the density of Zinc alloy is not affected by the pressure of the hydrogen gas in the same range of pressure. Interestingly, it is observed that the size of the eutectic structure of the Zinc alloy decreases while the pressure of the hydrogen gas increases. This observation is worth further study.
48
Becker, Christian Guy. "Cure shrinkage control in polymerization of multicomponent resin systems with phase separation." Thesis, 1993. http://hdl.handle.net/1911/13691.
Full textAbstract:
This work investigates the volume changes effected during multicomponent resin polymerization/crosslinking (cure shrinkage) in an effort to reduce or eliminate this phenomenon (zero-shrinkage polymerization). The systems under study contained: a polyfunctional monomer; a second, difunctional low-boiling monomer; and a thermoplastic polymer additive. These components are miscible forming a single (transparent) phase, which remains stable and shows the expected cure shrinkage in slow polymerization. Upon rapid cure (within 2-10 minutes) these systems undergo phase separation and show significantly reduced cure shrinkage, attaining zero shrinkage within certain composition ranges. Experimental evidence based on Scanning Electron Microscopy, polymerization under pressure, photopolymerization, and solvent extraction indicates that the reduction in cure shrinkage is due to the nucleation and growth of vapor bubbles of the low-boiling monomer within separate microdomains formed during rapid polymerization and precipitated by the high temperatures attained at peak exotherm, as well as negative hydrostatic pressures arising from cure shrinkage of the crosslinked polymer phase.
49
Wu, Jia-Yuan, and 吳嘉原. "Adhesion-induced Phase Separation ofBiomembranes—Effective Potential and Simulations." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/7k8zf8.
Full textAbstract:
碩士國立中央大學
物理研究所
94
We present theoretical analyses and numerical simulations for the adhesion-induced phase separation of multi-component membranes with two types of ligand-receptor complexes (junctions). We show that after integrating all possible distributions of the junctions, the system can be regarded as a membrane under an effective external potential. Mean field theory and Gaussian approximation are used to analyze the effective membrane potential and we find (i) The height difference of the junctions is the main factor that drives phase separation at sufficiently large junction height difference. (ii) In the two phase region far from the mean-field critical point, because of the higher entropy associated with the softer junctions, phase coexistence occurs when the effective binding energy of the more rigid junctions is higher. (iii) In the two phase region near the mean-field critical point, the shape of the effective potential shows that the phase coexistence occurs when the effective binding energy of softer junctions is higher. The effect of junction density on the critical point is studied by Monte Carlo simulations, and the result shows that phase separation occurs at larger junction height difference as junction density of the system decreases.
50
Chen, Jui-Shui, and 陳瑞穗. "Porous polylactide scaffolds prepared by thermally induced phase separation." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/62874430026093483385.
Full textAbstract:
碩士國立陽明大學
醫學工程研究所
90
Porous polylactide scaffolds have been extensively explored for drug delivery carriers and tissue engineering due to their biocompatibility. The porous scaffolds support for cell attachment、proliferation、migration、supply of nutrients should meet several requirements: highly porous and surface area、interconnected pore structure and good mechanic properties. In this research, we fabricated porous polylactide scaffolds with highly porous and interconnected structures by TIPS technique. The various porous structures can be easily obtained by adjusting thermodynamic and kinetic parameters. We investigated the main experimental parameters as molecular weight, concentration, temperature, and time that relate to morphology of PLA scaffolds. In addition, hydrophobic PLA scaffolds apply to cell transplantation can be efficiently wet by ethanol. We studied the dimension stability and microstructure of DLPLA scaffolds that prewetted by ethanol. The results show that inclusion of nonsolvent cause the polymer solution separated into two phases at high temperature easily. Liquid-liquid phase separation at 72℃ in 30wt%DLPLA with 85/15 dioxane/water mixture. On the other hand, Liquid-liquid phase separation wasn’t occurred in the polymer solution without DLPLA (100/0 dioxane/water mixture). The morphology of scaffolds shows a regular morphology at high molecular weight. Furthermore, pore size was increased with high phase separation temperature, long coarsening time, and high concentration of nonsolvent. The lacy-structure，interconnective and high porosity scaffolds were fabricated in spinodal decomposition mechanism. The DLPLA scaffolds structure was shrinkage after prewetted by pure ethanol, it leads to decrease the intrusion volume of buffer. Besides, dimension and microstructure of DLPLA scaffolds were not being shrunk by 50/50 ethanol/water in 30min. The treatment was suggested to ensure well water infiltration and microstructure stability properties.