Dissertations / Theses on the topic 'DIMETHYLSILOXANE'
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ʿAzīz, Ṭāriq. "Development of a poly (dimethylsiloxane) maxillofacial prosthetic material." Thesis, Cardiff University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.490389.
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Lewicki, James P. "The ageing behaviour of novel poly (dimethylsiloxane) nanocomposites." Thesis, University of Strathclyde, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487855.
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This thesis reports the formulation, characterisation and investigation of the ageing behaviour using a combination of dielectric spectroscopy and thermal analysis techniques of a series of novel polysiloxane nanocomposite elastomers which incorporate the organically modified Montmorillonite nano-clay Cloisite 6A and polyhedral oligomeric silsequioxane (POSS) as nano-scale fillers.
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Brown, David Alexander. "Ultrasonically assisted synthesis and degradation of poly(dimethylsiloxane)." Thesis, University of Bath, 1999. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.635432.
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Singh, Shanti. "Studies of the crystallization and morphology of poly(dimethylsiloxane)." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38284.
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A detailed analysis of the crystallization behaviour of poly(dimethylsiloxane) (PDMS) was undertaken. Determination of the equilibrium melting temperature showed a six degree difference between the equilibrium melting of a hydroxy terminated polymer (PDMS-OH, Tmo = 266 K, M w = 92.9 kg mol-1) over that of a trimethylsilyl terminated polymer (PDMS-CH3, Tmo = 260 K, Mw = 100 kg mol-1). The inherent flexibility of the Si-O linkage of these polymers caused crystallization to be first detected at Tmo - 35 K, and was recorded down to 177 K, i.e., Tg + 30 K. Both systems followed well behaved regime III surface nucleation kinetics. The average fold interfacial surface free energy, sigmae, was calculated to be 17.6 erg cm -2 and resulted in a very low value for the work of chain folding, q, calculated to be 14.6 kJ mol-1. This is in accord with the small rotational barrier of the siloxane backbone. In addition, PDMS-OH crystallized with slower kinetics than PDMS-CH3, verified by chemical conversion from the hydroxy to trimethylsilyl end group.The first reported detection of two different PDMS solid state morphologies is presented. A small population of very low birefringent (Deltan ) spherulites was observed to nucleate simultaneously with a majority of bright positive Deltan spherulites throughout the accessible crystallization temperature range. The sign of Deltan of these darker spherulites varied with growth, and this growth rate was depressed from that of the bright spherulites. Calorimetric annealing experiments indicate that the PDMS system attains very high percent crystallinities very early after nucleation. Coupled with the results of small angle laser light scattering (SALLS) during slow (1 deg/min) melting, secondary crystallization processes were observed to be non-negligible very soon after primary crystallization.
SALLS of the crystallizing PDMS system was sensitive to the concurrent effects of (i) the presence of dark spherulites, (ii) secondary crystallization, and (iii) the distribution of spherulite sizes. These combined effects generated significant non-ideality within V v and Hv scattering envelopes. The effects of (i) and (ii) caused both the Vv pattern to remain circularly symmetric throughout the entire crystallization timeframe, and the 4-leaf clover pattern of the Hv mode scattering to contain multiple intensity maxima not restricted to an azimuthal angle of 45°. The effect of (iii) was to lower the calculated SALLS average radial growth rate relative to that observed optically.
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Waugaman, Marlene. "Synthesis and characterization of 3-[Oligo(dimethylsiloxane] thiophene macromonomers." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 1998. http://digitalcommons.auctr.edu/dissertations/1293.
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Electronic conductive polymers such as polyacetylenes, polyanilines and polythiophenes, are not easy to process due to lack of tractability and solubility. Chemical modifications of the polythiophenes backbone have been utilized to improve the processibility.
Our goal is to synthesize and characterize 3-[oligo(dimethylsiloxane)]- thiophene macromonomers as precursors for potentially processible, conductive derivatives of polythiophene. The precursor will be used in the preparation of various poly {[3- oligo(dimethylsiloxane)]thiophene-co-3-methylthiophene} random copolymers. By increasing the chain length of the low glass transition (Tg) side chain, we hope to produce processible elastomeric material.
w-(Si-H)-DMS, 3-propenylthiophene (i.e. precursors for the macromonomers), and the macromonomer were characterized (as appropriate) by 'HNMR, SiNMR, C NMR, DSC, IR, UV-VIS, GPC, and GC-MS.
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Alonso, Bruno. "Materiaux hybrides poly-dimethylsiloxane-vanadate synthese, caracterisation et proprietes." Paris 6, 1998. http://www.theses.fr/1998PA066383.
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Cette these a eu pour objet principal la synthese, la caracterisation et l'etude de proprietes mecaniques et optiques de materiaux poly-dimethylsiloxane-vanadate, gels ou reseaux polymeres resultant de l'hydrolyse d'alcoxydes de silicium et de vanadium (v). Les principaux resultats concernent l'etude des interactions entre unites dimethylsiloxane et unites vanadate tout au long des processus de formation et de degradation des gels, la description de la structure du gel et l'identication de correlations entre cette structure et les proprietes. Nous avons pu montre que la co-hydrolyse des precurseurs conduit a des materiaux plus stables que ceux obtenus par pre-hydrolyse du precurseur silice pour des rapports molaires v/si proches de 0,1. Cette particularite est liee aux roles oxophile et catalytique du vanadium (v) mais aussi a des affinites chimiques importantes avec les unites dimethylsiloxane qui permettent de contrecarrer dans un premier temps les processus de separation de phases. Les gels obtenus sont constituees de segments dimethylsiloxane courts (5 a 6 unites en moyenne) lies des unites vanadate tri-fonctionnelles isolees. Malgre cette homogeneite chimique, nous avons pu a maintes reprises distinguer deux types de sites. Ils ont ete associes aux effets disjoints de la reticulation et de la terminaison des chaines.
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Preston, Christopher M. L. "Poly(dimethylsiloxane) : blends with poly(urethane) & radiation chemistry /." [St. Lucia, Qld.], 2000. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16169.pdf.
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Wang, Dan. "Surface modification of poly(dimethylsiloxane) with a perfluorinated alkoxysilane for selectivity toward fluorous tagged peptides." Kingston, Ont. : [s.n.], 2008. http://hdl.handle.net/1974/1205.
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Taori, Vijay Purushottam. "Synthesis and properties of bioinspired silica filled poly(dimethylsiloxane) networks." Cincinnati, Ohio : University of Cincinnati, 2005. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1116248554.
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Choi, Jae Won. "The plasma treatment of poly(dimethylsiloxane) for enhanced surface properties." Thesis, University of Surrey, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402622.
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Silva, Junior Elias Severo da 1981. "Preparação de fases estacionarias para CLAE com uma mistura de poli(dimetilsiloxano) e poli(metiloctadecilsiloxano) sorvidos e imobilizados por tratamento termico sobre silica." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249914.
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Orientador: Carol Hollingworth CollinsDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica
Made available in DSpace on 2018-08-08T23:26:20Z (GMT). No. of bitstreams: 1 SilvaJunior_EliasSeveroda_M.pdf: 1708075 bytes, checksum: 992e31e82bde038aa81939043b9dd1a7 (MD5) Previous issue date: 2007
Resumo: Neste trabalho foram feitos estudos de otimização das condições de preparo de fases estacionárias para uso em Cromatografia Líquida de Alta Eficiência em fase reversa (CLAE-FR) da mistura de poli(dimetilsiloxano) (PDMS) e poli(metiloctadecilsiloxano) (PMODS), sorvidos e imobilizados por tratamento térmico (em atmosfera inerte) na superfície de sílica Kromasil (esférica, 5 mm). As fases estacionárias foram avaliadas por testes químicos, físicos, cromatográficos e de estabilidade em fases móveis em condições agressivas. As melhores condições de preparo das fases estacionárias foram: sorção de 25 % PMODS e 25 % PDMS sobre sílica, mantendo 15 dias de repouso, e imobilizados a 128 °C durante 8 horas e 40 minutos. As fases estacionárias preparadas nas melhores condições apresentaram eficiências de 60000 e 38000 pratos m, respectivamente, para os compostos naftaleno e N,N-dimetilanilina, além de picos simétricos mesmo para compostos ácidos (fenol) e básicos (N,N-dimetilanilina). O estudo de caracterização através das misturas-teste de Tanaka indicou a presença de silanóis residuais, mas os resultados dos parâmetros avaliados foram razoáveis, principalmente comparados a fases PMODS, PDMS e algumas comerciais. Quanto aos testes de estabilidade, a FE manteve-se estável durante 250 volumes de coluna para o teste básico apresentando queda significativa da eficiência (60%) para o naftaleno e pequena variação na assimetria para os compostos naftaleno e N,N-dimetilanilina, já no teste ácido a FE manteve-se estável por 950 volumes de coluna apresentando uma queda suave na eficiência (10%) e variações na assimetria a partir de 400 volumes de coluna, ambos para o acenafteno, porém o fator de retenção caiu nos dois testes indicando a perda de parte da mistura polimérica
Abstract: In this work the conditions for the preparation of a stationary phase of use in reverse phase high performance liquid cromatography (RP-HPLC) with a mixture of poly(dimethylsiloxane) (PDMS) and poly(methyloctadecilsiloxane) (PMODS) sorbed and immobilized by thermal treatment (in an inert atmosphere) on Kromasil silica (spherical, 5 mm) were optimized. The stationary phases were evaluatied by chemical, physical and chromatographic tests and for stability in mobile phases having agressive conditions. The best conditions for preparation of the stationary phases were: sorption of 25 % PMODS and 25 % PDMS on to the silica, storing for 15 days and then immobilizing at 128 °C for 8 hours and 40 minutes. The stationary phases from these conditions showed efficiencies of 60000 and 38000 plates m for naphthalene and N,N-dimethylaniline and symmetrical peaks for acidic (phenol) and basic (N,N-dimethylaniline) compounds. A characterization study using Tanaka's test-mixture indicated the presence of residual silanols, but evaluation parameters were still resonable, compared to PMODS, PDMS and some commercials phases. In the stability tests the stationary phase was for stable 250 column volumes in the basic test, showing a decrease of efficiency (60 %) for naphthalene but little change in asymmetry for naphthalene and N,Ndimethylaniline. In the acid test the stationary phase maintained efficiency for 950 column volumes with some decrease in efficiency (10 %) but showed a small change in asymmetry after 400 column volumes for acenaphtene. However, the retention factor fell in both tests, showing partical loss of the polymeric mixture without changing the coverage of the support
Mestrado
Quimica Analitica
Mestre em Química
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Barjovanu, Raluca A. "Poly(ferrocenyldimethylsilane)-b-Poly(dimethylsiloxane) micelles, morphology control through composition variation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0029/MQ63246.pdf.
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Becker, Geoffrey A. "The determination of hemocompatibility of a geometrically-altered poly(dimethylsiloxane) surface." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32879.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (leaves 38-40).
Bio- and hemocompatibility are some of the driving forces behind medical device creation and materials science in this day and age. An experimental study was performed to test whether a geometrically altered surface of Poly(dimethylsiloxane), or PDMS, was found to be more or less hemocompatible than a flat, unaltered film of PDMS. In this case, the alteration was the addition of micron-scale posts sticking perpendicular to the surface, creating a superhydrophobic "bed of nails" effect. Once the specific altered surfaces were chosen, designed using Photolithography, and manufactured via a polymer casting process, a platelet adhesion assay was developed to assess the relative hemocompatibility of the surface via number of platelets counted on the surface of the altered vs. unaltered PDMS. Apparent contact angles of blood and Platelet-Rich Plasma (PRP) on the surface were also measured. The final instance of this experiment yielded positive results: The geometrically altered surface yielded less debris and platelet adhesion than did the flat PDMS surface, indicating an improvement in the hemocompatibility of PDMS via this process.
by Geoffrey A. Becker.
S.B.
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Pussadee, Nirut. "Poly(dimethylsiloxane) Based Micro- and Nanofluidic Device Fabrication for Electrophoresis Applications." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1268179904.
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Mecham, Jeffrey Brent. "Synthesis and Characterization of Cycloaliphatic and Aromatic Polyester/Poly(dimethylsiloxane) Segmented Copolymers." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/31382.
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Linear thermoplastic polyesters are commonly used in high volume applications such as food containers, films and textile fibers. The physical and mechanical properties of these materials are well documented and are a function of chemical structure and morphology (e.g. semi-crystalline, amorphous, etc.). Polyesters, as are many organic polymers, are quite flammable.
Polydimethylsiloxane homopolymer exhibits low mechanical strength and, even at high molecular weight, exists as a viscous fluid rubbery gum due to its low glass transition temperature of approximately -123°C. However, one of the many attractive properties of this polymer is its relatively low flammability and if properly designed, organic â sand-likeâ silicates are produced in oxidizing atmospheres at elevated temperatures (e.g. 500-700°C).
This thesis discusses the synthesis and characterization of novel, high molecular weight cycloaliphatic and aromatic polyester/ poly(dimethylsiloxane) segmented copolymers. The cycloaliphatic copolymers were synthesized via a melt process using a high trans content 1,4 dimethylcyclohexanedicarboxylate, and 1,4 butanediol or cyclohexanedimethanol, while the partially aromatic systems were synthesized using dimethyl terephthalate and butanediol. Primary and secondary aminopropyl terminated poly(dimethylsiloxane) oligomers of controlled molecular weight were endcapped with excess diester to form an amide linked diester terminated oligomer. The latter was then incorporated into the copolymer via melt transesterification to afford a multiphase segmented copolymer. Selected compositions showed enhanced ductility and hydrophobic surface modification.
The polysiloxane segment was effeciently incorporated into the copolymers and was unaffected by the transesterification catalyst under typical reaction conditions.
The homopolymers and copolymers were characterized by solution, thermal, and mechanical, and surface techniques. The segmented copolymers were demonstrated to be microphase separated as determined by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and transmission electron microscopy. The surface of the copolymers was enriched with the polysiloxane segment as evidenced by contact angle analysis.
Thermal gravimetric analysis of the segmented copolymers containing identical amounts of PDMS, but varying in the primary or secondary nature of their amide linkages, exhibited quantitatively identical char yields and weight loss behavior. The segmented copolymers exhibited char yields in air superior to those of their respective homopolymers.
Additionally, aromatic poly(tetramethyleneoxide) (PTMO) based polyether/polyester segmented copolymers were modified with poly(dimethylsiloxane). DMA revealed an apparent shift (higher Tg) of the PTMO segment reflecting an increase in phase mixing with the â hardâ polyester segment, possibly induced by the hydrophobic PDMS phase.Master of Science
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Lachhman, Shem Benjamin. "Roller-Cast Poly-Dimethylsiloxane as a Non-Hermetic Encapsulant for MEMS Packaging." Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1323445335.
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Chaudhry, Amiya Nur. "Characterisation and degradation of a typical RTV silica filled poly(dimethylsiloxane)(PDMS) foam." Thesis, University of Sussex, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398356.
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Sun, Di. "CHARACTERIZATION OF MEDICAL GRADE POLY-DIMETHYLSILOXANE AS ENCAPSULATION MATERIALS FOR IMPLANTABLE MICROELECTROMECHANICAL SYSTEMS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1396631435.
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Petet, Thomas J. Jr. "Characterization of Poly(dimethylsiloxane) Blends and Fabrication of Soft Micropillar Arrays for Force Detection." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4649.
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Diseases involving fibrosis cause tens of thousands of deaths per year in the US alone. These diseases are characterized by a large amount of extracellular matrix, causing stiff abnormal tissues that may not function correctly. To take steps towards curing these diseases, a fundamental understanding of how cells interact with their substrate and how mechanical forces alter signaling pathways is vital. Studying the mechanobiology of cells and the interaction between a cell and its extracellular matrix can help explain the mechanisms behind stem cell differentiation, cell migration, and metastasis. Due to the correlation between force, extracellular matrix assembly, and substrate stiffness, it is vital to make in vitro models that more accurately simulate biological stiffness as well as measure the amount of force and extracellular matrix assembly. To accomplish this, blends of two types of poly(dimethylsiloxane) (PDMS) were made and the material properties of these polymer blends were characterized. A field of 5µm or 7µm microscopic pillars (referred to as posts) with a diameter of 2.2µm were fabricated from these blends. Each combination of PDMS blend and post height were calibrated and the stiffness was recorded. Additionally, polymer attachment experiments were run to ensure cells survived and had a normal phenotype on the different blends of PDMS when compared to pure PDMS. Finally, cells were placed onto a field of posts and their forces were calculated using the new stiffness found for each blend of post. Varying the PDMS material stiffness using blends allow posts to be much more physiologically relevant and help to create more accurate in vitro models while still allowing easy and accurate force measurement. More biologically relevant in vitro models can help us acquire more accurate results when testing new drugs or examining new signaling pathways.
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Diop, Amadou Lamine. "NANOCOMPOSITES POLY(DIMETHYLSILOXANE) - SILICE OU OXYDE DE TITANE GENERE IN SITU : SYNTHESE, STRUCTURE ET PROPRIETES." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2010. http://pastel.archives-ouvertes.fr/pastel-00578502.
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La présente étude examine et compare le comportement de deux nanocomposites à base de particules sphériques (SiO2 et TiO2) générées in situ au sein d'une matrice PDMS par le procédé sol-gel. La synthèse des réseaux PDMS-SiO2 et PDMS-TiO2 a été effectuée en utilisant plusieurs catalyseurs pour obtenir des morphologies différentes. Pour le suivi des réactions de synthèse et la détermination des taux de silice ou d'oxyde de titane, la pesée et la spectroscopie infrarouge ont été utilisées. La morphologie, l'état de dispersion, l'interaction polymère-charge, la dégradation thermique et les propriétés mécaniques ont été caractérisés et comparés au travers de plusieurs méthodes : 1) La spectroscopie IR à transmission pour la présence d'eau dans les nanocomposites ; 2) La MET et le SANS pour la dispersion et la morphologie ; 3) La DSC, la RMN du proton, la TSDC et le gonflement pour l'interaction polymère-charge ; 4) L'ATG pour la dégradation thermique ; 5) La Traction unixiale et la mesure dynamique pour les propriétés mécaniques. Des différences et des similitudes ont été observées entre les réseaux PDMS-SiO2 et PDMS-TiO2. Les deux types de réseaux aboutissent à un bon renforcement avec une amélioration des modules élastiques et des propriétés de rupture selon le catalyseur utilisé. Des différences apparaissent sur la forme des courbes de traction (avec un comportement plastique plus marqué sur les échantillons TiO2) et on note l'absence d'effet Payne pour les réseaux PDMS-SiO2 contrairement aux réseaux PDMS-TiO2. Les systèmes PDMS-SiO2 montrent une amélioration des propriétés thermiques par rapport au réseau non-chargé. De plus cette amélioration est liée aux conditions de synthèse et notamment à la nature du catalyseur. En effet, l'amélioration des propriétés thermiques est meilleure dans les échantillons catalysés avec le DEA. Pour les échantillons PDMS-TiO2, on a plutôt une dégradation des propriétés thermiques, les échantillons chargés de TiO2 se dégradant plus vite que le réseau non chargé et à plus faible température. Toutes les différences et similitudes observées ont pu être reliées à la nature de la charge, à la différence de morphologie (taille des particules, existence d'un réseau percolant de charge etc...) et à la qualité de l'interface PDMS-SiO2 ou PDMS-TiO2.
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O'Brien, Kristen Wilson. "Synthesis of Functionalized Poly(dimethylsiloxane)s and the Preparation of Magnetite Nanoparticle Complexes and Dispersions." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/28869.
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Poly(dimethylsiloxane) (PDMS) fluids containing magnetite nanoparticles stabilized with carboxylic acid-functionalized PDMS were prepared. PDMS-magnetite complexes were characterized using transmission electron microscopy, elemental analysis, and vibrating sample magnetometry. PDMS-magnetite complexes containing up to 67 wt% magnetite with magnetizations of ~52 emu gram-1 were prepared. The magnetite particles were 7.4 ± 1.7 nm in diameter. Calculations suggested that the complexes prepared using mercaptosuccinic acid-functionalized PDMS (PDMS-6COOH) complexes contained unbound acid groups whereas the mercaptoacetic acid-functionalized PDMS (PDMS-3COOH) complexes did not. Calculations showed that the PDMS-3COOH and PDMS-6COOH covered the same surface area on magnetite. Calculations were supported by molecular models and FTIR analyses. The complexes were dispersed into PDMS carrier fluids by ultrasonication, resulting in magnetic PDMS fluids with potential biomedical applications.
Magnetite particles (100 nm to 1 mm in diameter) were prepared by crystallization from goethite/glycol/water solutions under pressure. Two methods for particle growth were investigated in which the crystallization medium was varied by adjusting the amount of water or by adding itaconic acid. Particle surfaces were analyzed by x-ray photoelectron spectroscopy (XPS). Particles with clean surfaces were coated with carboxylic acid-functionalized poly(e-caprolactone) stabilizers. Adding itaconic acid to the reactions afforded particles ~100 nm in diameter. The magnetite particles displayed magnetic hysteresis. The particles were dispersed into vinyl ester resins by ultrasonication and it was demonstrated that the ~100 nm particles remained dispersed for three days without agitation. These dispersions have applications in magnetic induction heating for composite repair.
Living polymerizations of hexamethylcyclotrisiloxane were terminated with dimethylchlorosilane, phenylmethylchlorosilane, or diisopropylchlorosilane (DIPCS). Platinum-catalyzed hydrosilation of the hydrosilane-terminated PDMS with allyloxyethanol afforded a systematic series of hydroxyalkyl-terminated PDMS. The reactions were successful except for the hydrosilation of the sterically-hindered DIPCS-functionalized PDMS where no reaction was observed. Hydroxyalkyl-terminated PDMS oligomers were successful in initiating the stannous octoate-catalyzed copolymerization of e-caprolactone, which afforded PDMS-b-PCL diblock copolymers of controlled composition.Ph. D.
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SCHREYECK, GABRIEL. "Comportement de copolymeres amphiphiles a l'interface polymere/polymere. Cas du systeme poly(dimethylsiloxane)/poly(oxyethylene)." Université Louis Pasteur (Strasbourg) (1971-2008), 1998. http://www.theses.fr/1998STR13003.
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L'interface entre le poly(dimethylsiloxane) (pdms) et le poly(oxyethylene (poe) en presence ou non de copolymere pdms-poe a ete etudiee par tensiometrie a goutte pendante et reflectometrie des rayons x. Pour l'interface pdms/poe, la tension interfaciale reste constante au cours du temps. Sa decroissance lineaire avec la temperature est d'environ 0,01 mn. M#-#1. K#-#1. Elle augmente avec la masse moleculaire des homopolymeres comme 1-km#-#x, avec x plus proche de 1 que de 2/3, pour tendre vers une valeur limite. L'interface se forme instantanement et son epaisseur est tres faible (inferieure au nm). Pour l'interface pdms/poe en presence de copolymere, la tension interfaciale decroit lentement ou passe par un minimum (inattendu) au cours du temps avant d'atteindre sa valeur d'equilibre, selon la concentration en copolymere dans le poe. Cette cinetique de formation de l'interface a ete expliquee en considerant deux processus : l'adsorption du copolymere a l'interface par transfert au-dessus d'une barriere d'energie et la relaxation de la couche interfaciale. La tension interfaciale a l'equilibre diminue continument en fonction de la concentration en copolymere. En termes de gibbs, cela traduit l'adsorption preferentielle du copolymere a l'interface. Un copolymere est d'autant plus efficace pour reduire la tension interfaciale que sa masse est importante et que sa structure se rapproche de celle d'un copolymere a blocs. Des films minces de pdms et poe, obtenus par depot sur des substrats solides hydrophobes et hydrophiles, ont des epaisseurs, mesurees par reflectivite des rayons x, de quelques dizaines de nm. Les films de pdms ont une faible rugosite de surface. Les films de poe apparaissent stratifies, ils sont instables. Apres homogeneisation par recuit, le demouillage du film, suivi par microscopie a force atomique, presente deux regimes : la formation d'un bourrelet a vitesse constante et la maturation durant laquelle la zone seche croit comme (temps)#2#/#3.
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Smith, Susan Abenes. "Synthesis and characterization of perfectly alternating segmented copolymers comprised of poly(dimethylsiloxane)s and engineering thermoplastics." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-03022010-020156/.
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MURUGESAN, SURESH. "IN SITU PREPARATION AND STRUCTURE - PROPERTY STUDIES OF FILLER PARTICLES IN POLY(DIMETHYLSILOXANE) ELASTOMERS." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1059393661.
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Fiorini, Gina S. "Polymeric microfluidic devices : development of thermoset polyester microfluidic devices and use of poly(dimethylsiloxane) devices for droplet applications /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/8627.
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Bayley, Gareth Michael. "Novel electrospun fibres of amphiphilic organic-inorganic graft copolymers of poly(acrylonitrile)-graftpoly( dimethylsiloxane) for silicone composite reinforcement." Thesis, Stellenbosch : Stellenbosch University, 2011. http://hdl.handle.net/10019.1/17875.
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Thesis (PhD)--Stellenbosch University, 2011.ENGLISH ABSTRACT: Novel silicone nanocomposites were prepared using poly(acrylonitrile) (PAN) based reinforcing fibres as well as multi-walled carbon nanotubes (MWCNTs). Compatibility of the fibre fillers with the silicone matrix required the synthesis of novel amphiphilic, organic–inorganic graft copolymers of PAN and poly(dimethylsiloxane) (PAN-g-PDMS). These fibre precursor materials were synthesised via the “grafting through” technique using conventional free radical copolymerisation. The PDMS macromonomer content in the feed was varied from 5 wt% to 25 wt% and the molecular weights of the macromonomer were 1000 g.mol-1 and 5000 g.mol-1. The solvent medium of the precipitation reaction was optimised at a volume ratio of 98% benzene to 2% dimethylformamide (DMF). Successful incorporation of PDMS yielded graft copolymer blend materials of PAN-g-PDMS, blended with PAN homopolymer and unreacted PDMS macromonomer. A gradient elution profile was developed to track the successful removal of the PDMS macromonomer via hexane extraction. The gradient profile showed that as the PDMS content in the feed increased, the number of graft molecules in the blend increased relative to the number of PAN homopolymer molecules. The crystallisability of the PAN segments was shown to decrease as the PDMS content increased. The synthesised polymer was used as precursor material for the electrospinning of fibre fillers. The electrospinning of the precursor material was successfully achieved using 100% DMF as electrospinning solution medium. The amphiphilic nature of the precursor material in DMF resulted in self-assembled aggregate structures in the electrospinning solution. An increasing PDMS content was shown to affect the aggregation of the precursor material, and resulted in an increase in the solution viscosity. The “gel-like” solutions limited the achievable fibre morphological control when altering conventional electrospinning parameters such as voltage, tip-to-collector distance, and solution concentrations. The rapid evaporation and stretching of the solution during electrospinning, combined with the phase segregated amphiphilic molecules in solution and the crystallisation of the PAN segments resulted in (non-equilibrium morphology) fully porous fibres. The crystallinity was shown to decrease after electrospinning of the fibre precursor materials. Successful incorporation of surface oxidised MWCNTs into the electrospun fibres was achieved. The content of nanotubes was varied from 2 wt% to 32 wt%. The MWCNTs reduced the mean fibre diameters by acting as cross-linkers between the PAN segments and increasing the solution conductivity. The nanotubes dispersed well throughout the porous structure of the fibres and aligned in the direction of the fibre axis. Fabrication of silicone composites containing nonwoven and aligned fibre mats (with 8 wt% MWCNTs in the fibres, and without) was successfully achieved. The compatibilisation of the PDMS surface segregated domains allowed excellent dispersion and interaction of the PAN based fibre fillers with the silicone matrix. Mechanical analysis showed improved properties as the PDMS content in the fibre increased. The highest PDMS content fibres did, however, exhibit decreased properties. This was ascribed to increased PDMS (soft and weak) content, decreased crystallinity and increased fibre diameter (lower interfacial area). Dramatic improvements in strength, stiffness, strain and toughness were achieved. The most significant result was an increase in strain of 470%. The mechanical results correlated with results of SEM analysis of the fracture surfaces. The dramatic improvements in properties were a result of the fibre strength and ductility, as well as the mechanism of composite failure.
AFRIKAANSE OPSOMMING: Nuwe silikonnanosamestellings is berei deur gebruik te maak van poli(akrilonitriel) (PAN) gebaseerde versterkende vesels wat multi-ommuurde koolstof nanobuisies bevat het. Versoenbaarheid van die vesels met die silikonmatriks het die sintese van nuwe amfifiliese, organies–anorganiese ent-kopolimere van PAN en poli(dimetielsiloksaan) (PAN-g-PDMS) benodig. Die vesel voorlopermateriaal is deur middel van ‘n “ent-deur” vryeradikaalkopolimerisasie gesintetiseer. Die inhoud van die PDMS makromonomeer in die reaksie het gewissel vanaf 5% tot 25%. Die gebruik van twee verskillende molekulêre massas makromonomere is bestudeer (1000 en 5000 g.mol-1). Die optimale oplosmiddelmengsel vir die neerslagreaksie was 'n volume verhouding van 98% benseen tot 2% dimetielformamied (DMF). Suksesvolle insluiting van PDMS het versnitmateriale van PAN-g-PDMS kopolimere gemeng met PAN homopolimere en ongereageerde PDMS makromonomere gelewer. 'n Gradiënteluering- chromatografiese profiel is ontwikkel om die suksesvolle verwydering van die PDMS makromonomere via heksaanekstraksie te bepaal. Die gradiëntprofiel het aangetoon dat indien die PDMS inhoud in die reagense verhoog is, die aantal entmolekules relatief tot PAN homopolimeermolekules ook verhoog het. 'n Toename in PDMS inhoud het egter 'n afname in kristallisasie van die PAN segmente tot gevolg gehad. Die gesintetiseerde polimeer is gebruik as die beginmateriaal vir die elektrospin van veselvullers. Die elektrospin van die beginmateriaal was suksesvol wanneer 100% DMF as elektrospinoplosmiddel gebruik is. Die amfifiliese aard van die beginmateriaal in DMF lei tot outokonstruksie van aggregaatstrukture in die elektrospinoplossing. Toenemende PDMS inhoud beïnvloed die outokonstruksie van die molekules in oplossing en het gelei tot 'n toename in die oplossings se viskositeit. Die "gelagtige" oplossings beperk die haalbare vesel se morfologiese beheerbaarheid wanneer konvensionele elektrospin parameters soos elektriese spanning, punt-tot-versamelaar afstand, en oplossingkonsentrasies gewysig word. Die vinnige verdamping en strek van die oplossing tydens elektrospin, gekombineer met die fase-geskeide amfifiliese molekules in oplossing en die kristallisasie van die PAN segmente, het gelei tot (nie-ewewig morfologie) volledige poreuse vesels. Die kristalliniteit van die veselbeginmaterial het afgeneem nadat elektrospin toegepas is. Die insluiting van die oppervlak-geoksideerde multi-ommuurde koolstof nanobuisies in die elektrogespinde vesels was suksesvol. Die inhoud van die nanobuisies het gewissel van 2 wt% tot 32 wt%. Die MWCNTs het die gemiddelde veseldeursnit verminder deur op te tree as kruisbinders tussen die PAN segmente van die molekules. Die nanobuisies was goed versprei deur die poreuse struktuur van die vesels en dit was gerig in die rigting van die vesel-as. Bereiding van die silikonsamestellings bestaande uit nie-geweefde en gerigte veseloppervlakke (met en sonder 8 wt% multi-ommuurde koolstof nanobuisies in die vesel) was suksesvol. Die versoenbaarheid tussen die oppervlak van die PDMS-geskeide gebiede en die silikonmatriks laat uitstekende verspreiding en interaksie van die PAN-gebaseerde veselvullers met die silikonmatriks toe. Meganiese analise het aangetoon dat die fisiese eienskappe verbeter het namate die PDMS inhoud in die vesel vermeerder het. Die vesels met die hoogste PDMS inhoud het egter verswakte eienskappe getoon. Dit is toegeskryf aan ‘n verhoogde PDMS inhoud (sag en swak), ‘n afname in kristalliniteit en ‘n verhoogde veseldeursnit (laer grensoppervlakke). Dramatiese verbeterings in sterkte, styfheid, verlengbaarheid, vervorming en taaiheid is bereik. Die mees betekenisvolle gevolg was 'n toename in die verrekking van 470%. Die meganiese resultate is gekorreleer met SEM ontleding van die brekingsoppervlakke. Die veselkrag en vervormbaarheid, sowel as die meganisme van die splyting van die samestellings, het tot die dramatiese verbeterings in die meganiese eienskappe gelei.
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Zhang, Xiujuan. "Improvements in the Mechanical Properties of Some Biodegradable Polymers and Bimodal Poly(dimethylsiloxane) Hydrogels and Surface Hydrophilic Treatments." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1240666875.
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Lee, Sang Hak. "A PVTx study of the mixtures of the first three members of the linear dimethylsiloxane series with toluene /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu148732769562334.
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ROSATI, DAVID. "Etude physique et rheo-physique de copolymeres a blocs poly(styrene-dimethylsiloxane). Developpement d'un systeme d'analyse optique (trams)." Nice, 1998. http://www.theses.fr/1998NICE5227.
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L'objectif de ce travail de recherche est la mise au point d'un systeme (rheo-)optique ayant permis de mener a son terme l'etude physique et rheo-physique d'une serie de copolymeres a blocs poly(styrene-dimethylsiloxane). Dans un premier temps, nous avons donc concu un nouveau systeme d'analyse optique nomme trams. Cet outil se subdivise en deux modules distincts respectivement dedies au traitement des cliches de diffusion de la lumiere aux petits angles et aux mesures d'anisotropie optiques, tels que la birefringence ou le dichroisme, d'un echantillon soumis (ou non) a un champ exterieur de type rheologique, thermique et/ou radiations. L'utilisation de techniques informatiques modernes, nous a permis de mettre en place une configuration multitache, a partir de laquelle la mesure en temps reel d'une anisotropie optique et l'acquisition simultanee de cliches de diffusion est possible. L'utilisation du langage c/c++ couplee a une configuration optique (ou rheo-optique) simple rend ce systeme flexible et completement evolutif. En terme d'applications potentielles, cet outil peut etre utilise pour l'etude physique et rheo-physique des materiaux polymeres et des fluides complexes. Dans un second temps, nous presentons l'etude physique et rheo-physique des copolymeres a blocs fluides et microstructures. Elle se subdivise en trois parties globalement independantes : la synthese et la caracterisation physico-chimique, la rheologie des copolymeres de symetrie haute et la rheo-physique du seul dibloc cylindrique ayant un contraste optique d'orientation selon l'axe du gradient de vitesse d'un cisaillement simple. Enfin, une reflexion theorique sur la reponse viscoelastique des copolymeres diblocs lamellaires, parallelement orientes est egalement proposee.
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DiBartolomeo, Franklin. "HIGH SPEED CONTINUOUS THERMAL CURING MICROFABRICATION SYSTEM." UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_theses/105.
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Rapid creation of devices with microscale features is a vital step in the commercialization of a wide variety of technologies, such as microfluidics, fuel cells and self-healing materials. The current standard for creating many of these microstructured devices utilizes the inexpensive, flexible material poly-dimethylsiloxane (PDMS) to replicate microstructured molds. This process is inexpensive and fast for small batches of devices, but lacks scalability and the ability to produce large surface-area materials. The novel fabrication process presented in this paper uses a cylindrical mold with microscale surface patterns to cure liquid PDMS prepolymer into continuous microstructured films. Results show that this process can create continuous sheets of micropatterned devices at a rate of 1.9 in2/sec (~1200 mm2/sec), almost an order of magnitude faster than soft lithography, while still retaining submicron patterning accuracy.
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Qin, Yubo. "Developing a Poly(Dimethylsiloxane) (PDMS)/SU-8 (Negative Photoresist) Hybrid Microfluidic System for Sensitive Detection of Circulating Tumour Cells." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37892.
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Cancer is the second leading cause of death in the world. It is therefore critically important to detect cancer in its early stage to significantly increase the survival rate of cancer patients. Circulating tumour cells (CTCs) are cancer cells that peel off from primary tumour and enter bloodstream in early stage of a cancer, and thus it has been established that these CTCs are reliable targets for early cancer diagnosis. However, background signal reduction and optimization of CTC capturing mechanisms are still significant challenges in CTC detections with high sensitivities and accuracies. To this end, we have developed an aptamers and dendrimers based ultra non-fouling microfluidic detection system for sensitive detections of circulating tumour cells.
More specifically, we demonstrate a simple strategy to bind PDMS and SU-8 surfaces in order to prepare a hybrid microfluidic device and subsequently modify both surfaces simultaneously using poly(amidoamine) (PAMAM), a highly hydrophilic dendrimer to improve non-fouling properties of the hybrid microfluidic channel. The resulting hybrid microfluidic system shows a remarkable non-specific adsorption suppression of 99.7% when tested with hydrophobic microbead suspension, an ultra non-fouling performance that has not been reported before. This is significantly important for detections with high sensitivities. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and water contact angle are used to characterize and confirm surface modifications. In addition, we investigate the combined effects of surface properties on surface non-fouling performance to both live and dead cells. (3-aminopropyl)-trimethoxysilane (APTMS), carboxyl functionalized PAMAM dendrimer (PAMAM-COOH) and amino functionalized PAMAM dendrimer (PAMAM-NH2) are used to provide different surfaces with various surface hydrophilicity, electric charge and roughness. We show that electric charge of a surface is the most important factor influencing non- specific adsorption of live cells to the surface while hydrophilicity/hydrophobicity of a surface is the most important factor for dead cells. Atomic force microscopy, water contact angle and microscopy are used to characterize and confirm surface modifications. To further exploit and improve capturing efficiency of target cancer cells, we investigate the effect of the length of spacers that tether capturing aptamer to the microfluidic surfaces on capturing performance of CCRF-CEM circulating tumour cells. Aptamers with different lengths of thymine base spacers are immobilized onto PAMAM dendrimer modified surfaces in microfluidic channels. We demonstrate that ten thymine bases spacer has the best length for sgc8 aptamer to form its secondary structure for CCRF-CEM cell capture. Water contact angle, and microscopy are used to characterize and confirm surface modifications. Taken together, the results of this study significantly highlight the importance of different considerations on surface modification and its optimizations when designing a microfluidic system for high sensitivity detection and biosensing applications.
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JADHAV, ABHIJIT VILAS. "SYNTHESIS OF POLYSTYRENE PARTICLES IN SUPERCRITICAL CARBON DIOXIDE USING NOVEL SURFACTANTS." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1090938261.
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Sharfeddin, Asma Sharfeddin. "Mechanotransduction of Matrix Stiffness Regulates Cell Adhesion Strength: An Analysis Using Biomaterial Surfaces with Tunable Mechanical and Chemical Properties." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6387.
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Cells have the ability to sense the rigidity of the extracellular matrix which directly affects the control of cellular functions in development, wound healing and malignant transformation. Polydimethylsiloxane elastomers are useful model biomaterials for mechanotransduction studies because they possess several advantages including ease of fabrication, tunable elasticity and modifiable surface chemistry. In this work, we are investigating the influence of matrix stiffness on adhesion strength and the mechanosensory structures that regulate these processes. In addition, the effect of surface modifications to this elastic substrate system on other physical properties such as local stiffness and topography will be analyzed. Based on previous research, we hypothesized that cell adhesion dependent processes will be regulated by matrix stiffness, but that surface chemistry influences on protein adsorption could provide overriding regulatory signals. The results of this research will provide insight into the interconnected processes of mechanosensing and cell adhesion strengthening, and reveal criteria for designing instructive biomaterials with specific mechanical and chemical properties.
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Guha, Ingrid F. "Effects of silica nanoparticle surface treatment and average diameter on the physical and mechanical properties of poly(dimethylsiloxane)-silica nanocomposites." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/118564.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 35-37).
The purpose of this thesis was to quantify the effects of silica nanoparticle surface treatments and average silica nanoparticle diameter on various macroscopic properties of poly(dimethylsiloxane)-silica nanocomposites, specifically stiffness, wettability, and permeability to organic solvents. Poly(dimethylsiloxane)-silica nancomposites were prepared with constant amounts (4.8 wt%, 1.8 vol%) of fumed silica nanoparticles with varying surface treatments (hexamethyldisilazane and octamethylcyclotetrasiloxane) and varying particle diameter (7 and 12 nm). The Young's elastic modulus, mass increase due to dodecane absorption after 10 minutes, and advancing and receding water contact angles were measured for each nanocomposite. PDMS-silica nanocomposites containing untreated silica nanoparticles were found to have a higher Young's elastic modulus than nanocomposites containing hexamethyldisilazane-treated silica nanoparticles with the same diameter. However, nanocomposites containing identically sized silica nanoparticles with and without the octamethylcyclotetrasiloxane surface treatment had the same stiffness. The average nanocomposite stiffness increased slightly as the untreated silica nanoparticle diameter decreased from 12 nm to 7 nm. Varying the surface treatment or particle diameter of the filler did not significantly affect the level of dodecane absorption or the wettability of the nanocomposite. All nanocomposites showed approximately 20-23 wt% increase from dodecane absorption after 10 minutes of dodecane immersion. All nanocomposites exhibited average advancing contact angles around 115-120° and average receding contact angles around 85-90°. Nanocomposites were imaged using optical coherence tomography to examine particle dispersion. Potential differences in particle dispersion are discussed.
by Ingrid F. Guha.
S.B.
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Stubbs, Ian. "Poly(styrene)-b-Poly(dimethylsiloxane)-b- Poly(styrene)/Single Walled Carbon Nanotube Nanocomposites. Synthesis of Triblock Copolymer and Nanocomposite Preparation." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2016. http://digitalcommons.auctr.edu/cauetds/49.
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Molecular weights of 2,000, 6,000 and 10,000 of silane functionalized atactic polystyrene (aPS) and α,ω-divinyl functionalized polydimethylsiloxane (PDMS) were prepared via living anionic polymerization and bulk anionic ring opening polymerization respectively. Functionalization of the homopolymers was confirmed by FT-IR and 1H-NMR spectroscopy and their molecular weights were determined via 1H-NMR end group analysis. A hydrosilylation reaction between the functionalized homopolymers of different molecular weights produced nine polystyrene-block-polydimethylsiloxane-block-polystyrene (aPS-b-PDMS-b-aPS) triblock copolymers. Field emission scanning electron microscopy observations revealed the copolymers self-assemble into supramolecular structures. Dynamic Light Scattering measurements show only small increase in the order of nanometers of its hydrodynamic radius as the individual molecular weights of the homopolymers were increased.
Nanocomposites of the copolymers were prepared by incorporating 1% of oxidized single walled carbon nanotubes (SWNTs) within the aPS-PDMS-aPS matrices via coagulation precipitation. Differential scanning calorimetry (DSC) thermal analysis shows the SWNT interacting with both aPS and PDMS constituting blocks. SWNTs interaction with aPS block either increases the polymer glass transition temperature (Tg) by restricting its segmental motion or decreases the Tg by a plasticization effect. Within the PDMS block the SWNTs act as nucleating sites accelerating the crystallization rate of the polymer. This is evident by the appearance of single and double melting endotherms in the DSC thermograms.
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Silva, Junior Elias Severo da 1981. "Preparação de fases estacionárias para CLAE com uma mistura de poli(dimetilsiloxano) e poli(metiloctadecilsiloxano) sorvidos e imobilizados por tratamento térmico sobre sílica metalizada." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249933.
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Orientador: Carol Hollingworth CollinsTese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
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Resumo: Neste trabalho foram feitos estudos das condições de preparo de fases estacionárias para uso em Cromatografia Líquida de Alta Eficiência em Fase Reversa (CLAE-FR) da mistura de poli(metiloctadecilsiloxano) (PMODS) e poli(dimetilsiloxano) (PDMS), sorvidos e imobilizados por tratamento térmico (em atmosfera inerte) na superfície de sílica Kromasil (esférica, 5 µm) metalizada com titânia ou zircônia. As fases estacionárias foram avaliadas por testes químicos, físicos, cromatográficos e de estabilidade em fases móveis em condições agressivas. As melhores condições de preparo das fases estacionárias foram: sorção de 22 % de PMODS e 33 % de PDMS sobre sílica metalizada, mantendo períodos de 4 e 10 dias em repouso, respectivamente, após adição de cada polímero e depois imobilizados a 120 °C durante 16 horas. As fases estacionárias preparadas nas melhores condições apresentaram eficiências superiores a 45000 e 10000 pratos m-1, respectivamente, para os compostos naftaleno e N,N-dimetilanilina, além de picos simétricos para a maioria dos compostos. O estudo de caracterização através das misturas testes de Tanaka, Engelhardt, Neue e SRM 870 indicou a presença de silanóis residuais, mas os resultados dos parâmetros avaliados foram satisfatórias, principalmente comparados às fases PMODS e algumas comerciais. Quanto aos testes de estabilidade em meio básico as fases estacionárias mantiveram-se estáveis durante 550 e 800 volumes de coluna, respectivamente, SiTi(PMODS + PDMS) e SiZr(PMODS + PDMS), usando o acenafteno. Já no teste ácido as fases estacionárias mantiveram-se estáveis por 900 e 800 volumes de coluna, respectivamente, para SiTi(PMODS + PDMS), e SiZr(PMODS + PDMS). As fases estacionárias SiTi(PMODS + PDMS), e SiZr(PMODS + PDMS), sorvidas e imobilizadas por tratamento térmico, apresentam potencialidade na separação de diferentes classes de compostos, tais como, agrotóxicos e fármacos
Abstract: In this work the conditions for the preparation of stationary phases for use in reversed phase high performance liquid chromatography (RP-HPLC) with a mixture of poly(methyloctadecilsiloxane) (PMODS) and poly(dimethylsiloxane) (PDMS) sorbed and immobilized by thermal treatment (in an inert atmosphere) on metalized (titanium and zirconium) Kromasil silica (spherical, 5 µm) were studied. The stationary phases were evaluatied by chemical, physical and chromatographic tests and for stability in mobile phases having agressive conditions. The best conditions for preparation of the stationary phases were: sorption of 22 % PMODS and 33 % PDMS onto the metalized silica, storing for 14 days and then immobilizing at 120 °C for 16 hours. The stationary phases from these conditions showed higher efficiencies of 45000 and 10000 plates m-1 for naphthalene and N,N-dimethylaniline and symmetrical peaks for most compounds. Characterization studies using Tanaka¿s, Engelhardt¿s, Neue¿s and the SRM 870 test-mixtures indicated the presence of residual silanols, but evaluation parameters were still reasonable, compared to PMODS phases and to commercials phases. In the adverses stability tests the stationary phase was for stable 550 and 800 column volumes, respectively, for SiTi(PMODS + PDMS) and SiZr(PMODS + PDMS), in the basic test, showing a decrease of efficiency (60 %) for N,N-dimethylaniline. In the acid test the stationary phases maintained efficiency for 900 and 800 column volumes, respectively, for SiTi(PMODS + PDMS) and SiZr(PMODS + PDMS). The stationary phases SiTi(PMODS + PDMS) and SiZr(PMODS + PDMS) sorbed and immobilized by thermal treatment, showed potential for the separation of different compounds classes, such as, pesticides and pharmaceuticals
Doutorado
Quimica Analitica
Doutor em Ciências
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ZHOU, DONGHUI. "EVALUATION OF THE CORRELATION BETWEEN PROPERTIES AND STRUCTURE OF POLYMER NANOCOMPOSITES." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1121126001.
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Klasner, Scott A. "Novel capillary and microfluidic devices for biological analyses." Diss., Manhattan, Kan. : Kansas State University, 2010. http://hdl.handle.net/2097/3747.
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Meltz, Freda-Jean. "Amphiphilic electrospun fibres of poly(methacrylic acid)-graft-poly(dimethylsiloxane) copolymers as a means to controlling electrospun fibre morphology and obtaining nanofibre hydrogels." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86620.
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Thesis (MSc)--Stellenbosch University, 2014.ENGLISH ABSTRACT: Novel poly(methacrylic acid)-graft-poly(dimethylsiloxane) copolymers were synthesised by conventional free radical reactions using a poly(dimethylsiloxane) macromonomer. The polymers were electrospun to investigate how the fibre morphology can be modified by manipulating the electrospinning solution parameters, and to determine the possibility of using the polymers as new materials for the production of polymer nanofibre hydrogels. The electrospinning solution parameters were varied by electrospinning the highly amphiphilic copolymers in solvents with variable solvent qualities. Scanning Electron Microscopy (SEM) and Field Emission Scanning Electron Microscopy (FE–SEM) was used to investigate the fibre morphology. Internal morphology was studied using a freeze fracture technique prior to FE-SEM imaging. It is revealed that the polymers in this study does not form any fine structure or pores even when self-assembled structures are present in the solution. Attempts were made to visualise any self-assembled structures of films produced from dilute solutions using TEM. Further studies included investigating the fibres properties, primarily with regards to their rate and extent of moisture and water uptake. The fibres showed hydrogel behaviour and the PDMS content were found to have an impact on the hydrogel stability. Post electrospinning crosslinking of the nanofibres was also explored.
AFRIKAANSE OPSOMMING: Unieke ent-kopolimere wat bestaan uit poli(metielakrielsuur) (PMAS) en poli(dimetielsiloksaan) (PDMS) is gesintetiseer deur middel van 'n “ent-deur” vryeradikaalkopolimerisasie. 'n PDMS makromonomeer is vir hierdie doel gebruik. Die polimere is geëlektrospin om vesels te vorm. Die doel was om die invloed van verkillende strukture in oplossing op die veselmorfologie te bepaal. Die moontlikheid om hierdie nanovesels as gels te gebruik is ook ondersoek. Die amfifiliese kopolimere is geëlektrospin uit die oplossing waarin dit wisselende oplosbaarheid toon. Skandeer elektron mikroskopie (SEM) is gebruik om die morfologie te ondersoek. Die interne morfologie van die vesels is ondersoek deur die vesels te vries en in die gevriesde toestand te breek. Die studie het getoon dat geen strukture op, of binne, die vesels vorm nie, selfs al moes daar assosiasie tussen segmente van die polimere gewees het. Hierdie tipe assosiasies sou strukture in die oplossing tot gevolg gehad het. 'n Poging is aangewend om die strukture in oplossing te visualiseer deur transmissie elektron mikroskopie (TEM) van dun films te ondersoek. Films is vanaf verdunde oplossings gevorm. Ander studies het ingesluit om die eienskappe van die vesels te ondersoek, met die fokus op hoeveel en hoe vinnig die vesels waterdamp en water kon absorbeer. Die vesels het soos 'n gel reageer. Hierdie gedrag is beïnvloed deur die hoeveelheid PDMS wat 'n definitiewe invloed op die stabiliteit van die gel gehad het. Kruisverbindings van die vesels, nadat dit geëlektrospin is, is ook ondersoek.
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KAYSER, DOMINIQUE. "Syntheses radicalaires de copolymeres sequences poly(dimethylsiloxane) poly(vinyliques) par la technique des iniferters. Preparation de nouveaux groupes fonctionnels actifs. Etudes cinetiques et caracterisations." Université Louis Pasteur (Strasbourg) (1971-2008), 1992. http://www.theses.fr/1992STR13184.
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Le travail realise s'inscrit dans le cadre de la mise au point de nouveaux procedes de polymerisation de monomeres vinyliques, bases sur l'utilisation de la technique des iniferters, en vue de synthetiser des copolymeres sequences poly(dimethylsiloxane)-poly(vinyliques) par voie radicalaire. Cette technique developpee recemment au laboratoire repose sur les proprietes thermiques des disulfures de thiurame, et sur la synthese de nouveaux groupements fonctionnels de type disulfures de bis-carbamyle. Elle consiste a introduire un ou plusieurs de ces groupements dans une macromolecule de poly(dimethylsiloxane) pour obtenir les macro et polyiniferters qui sont les precurseurs des copolymeres trisequences pdms-b-poly(vinyliques-b-pdms et multisequences pdms-b-poly(vinyliques)#n. Un interet particulier a ete porte a l'etude cinetique de la polymerisation du styrene et du methacrylate de methyle, en masse et en solution dans le toluene, amorcee par des macro et polyiniferters appartenant aux deux familles. Les principaux parametres cinetiques qui regissent ces polymerisations sont determines par exploitation mathematique des resultats experimentaux. La connaissance de ces grandeurs permet d'optimiser le procede de polymerisation et de synthetiser des copolymeres a teneur elevee en poly(dimethylsiloxane). La caracterisation morphologique de ces materiaux par diverses techniques physicochimiques met en evidence une heterogeneite de structure resultant de l'incompatibilite des sequences siloxane et methacrylate de methyle. Par ailleurs, ces composes presentent une excellente stabilite thermique ainsi qu'une bonne tenue au rayonnement uv
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Poojari, Yadagiri. "Enzyme Immobilization and Biocatalysis of Polysiloxanes." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1265987790.
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Snyder, Chad R. "Effect of chain structure on the thermodynamics and kinetics of polymer crystallization." Diss., This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-06062008-155543/.
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Laraba, Abbes Fazilay. "Etude des comportements hyperelastique et viscohyperélastique de deux élastomères de type NR et PDMS par extensométrie optique bidimensionnelle." Châtenay-Malabry, Ecole centrale de Paris, 1998. http://www.theses.fr/1998ECAP0567.
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Cette étude concerne la mise en place d'une méthodologie d'analyse de comportement en grandes déformations d'élastomères conditionnes en feuillards. Cette approche se base sur l'exploitation d'essais mécaniques balayant l'espace des sollicitations biaxiales. Ceci est rendu possible par la mise au point et l'adaptation d'une extensometrie optique bidimensionnelle aux grandes extensions de type caoutchoutique. Cette technique, basée sur la corrélation d'images, donne accès à l'évolution du tenseur des dilatations au cours d'un essai. Selon sa translucidité, le matériau est éclaire en lumière cohérente (effet speckle) ou en lumière blanche (mouchetis). Les matériaux étudies sont un caoutchouc naturel (nr) charge en noir de carbone, et un élastomère silicone (pdms) charge en silice. La caractérisation des comportements est basée sur l'interprétation de sollicitations homogènes de type traction simple et cisaillement pur, ainsi que des essais de structure sur éprouvettes a double entaille latérale (den). La haute définition spatiale de l'extensometrie optique permet en effet la mesure de profils de déformation à partir d'extensomètres locaux disposes le long de la section minimale des éprouvettes. La procédure d'optimisation, basée sur l'algorithme de levenberg-marquardt-fletcher couple au calcul analytique du hessien et du jacobien, a permis d'identifier un comportement hyperelastique (issu du potentiel de rivlin) pour le nr, et un comportement viscohyperelastique (modèle de maxwell adapte aux grandes déformations) pour le pdms. L'assouplissement sous contrainte (effet mullins) a également été pris en compte par une approche phenomenologique d'endommagement. Enfin, l'implémentation de ces formulations dans le code e. F. Systus, a permis la validation des lois identifies par comparaison des résultats numériques et expérimentaux obtenus sur les éprouvettes den. Cette méthodologie fiabilise ainsi l'identification du comportement, et ce grâce a l'essor de la photomécanique.
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Dagger, Anthony. "Investigations of hydrogenated and deuterated poly(dimethylsiloxanes)." Thesis, University of York, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265564.
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Le, Strat David. "Synthèse de nanocomposites modèles : contribution à l'étude des relations structures-propriétés mécaniques dans les élastomères renforcés." Phd thesis, Université Paris-Est, 2012. http://tel.archives-ouvertes.fr/tel-00804381.
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Les nanocomposites à matrice polymère et plus particulièrement les élastomères chargés intéressent depuis de nombreuses années la communauté scientifique du fait notamment de leurs bonnes propriétés mécaniques. Il est établi que l'amélioration des propriétés mécaniques observées dans les élastomères renforcés par des charges nanoscopiques est principalement due à des effets de structure (dispersion des charges) et à des effets d'interface (interactions charges/matrice). Afin d'alimenter la discussion sur l'origine du renforcement dans les élastomères chargés, cette étude s'intéresse à la synthèse et à la caractérisation de nanocomposites modèles pour lesquels les interactions charges/matrice et la microstructure sont maîtrisées. En parallèle, ce travail propose également une analogie entre ces systèmes et les ionomères, matériaux constitués de macromolécules sur lesquelles des groupements ioniques sont greffés. Ces matériaux ionomère présentent des propriétés originales et permettent la création de nœuds de réticulation réversibles avec la température
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Bendjama, Zoubida. "Extraction d'acétate d'éthyle de solutions aqueuses par pervaporation à travers des membranes en polydimethylsiloxane comportant divers degrés de réticulation." Vandoeuvre-les-Nancy, INPL, 1993. http://www.theses.fr/1993INPL030N.
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Parmi les domaines d'investigation concernant la pervaporation, nous avons choisi d'étudier l'extraction de substances organiques volatiles de milieux aqueux à travers un matériau polymère: le polydimethylsiloxane (PDMS). Le transfert pervaporatif d'un composé-type, l'acétate d'éthyle, a été modélisé. Le modèle établi permet la caractérisation des systèmes considérés à partir d'une seule opération de pervaporation. L'élaboration d'élastomères (PDMS), et la détermination de leurs propriétés physiques et mécaniques, nous ont permis de montrer que la dureté, le module d'élasticité, la température de transition vitreuse, la masse volumique et la masse moléculaire moyenne comprise entre deux nœuds de réticulation, sont étroitement liés aux conditions de préparation du matériau polymère. Leur application en sorption, diffusion et pervaporation et la confrontation des résultats obtenus révèlent la prédominance de la solvatation sélective dans le mécanisme de transfert en pervaporation. Dans toute la zone de miscibilité partielle, la constance des caractéristiques (gonflements et flux partiels) indique que dans ce cas la pervaporation est gouvernée par le gradient d'activité. Afin de prévoir les flux, nous avons eu recours au modèle de Flory-Huggins, en assimilant le système étudié a un pseudo-binaire. Cette modélisation permet de rendre compte du comportement des silicones testés dans tout le domaine de composition du mélange liquide
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Taori, Vijay P. "Synthesis and Properties of Bioinspired Silica Filled Polydimethylsiloxane Networks." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1116248554.
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Orrah, D. J. "Physical properties of cyclic and linear poly(dimethylsiloxanes)." Thesis, University of York, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381327.
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Mundry, Tobias. "Einbrennsilikonisierung bei pharmazeutischen Glaspackmitteln analytische Studien eines Produktionsprozesses /." Doctoral thesis, [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=958249938.
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Lansade, David. "Stabilisation de résines poly(diméthylsiloxane) en environnement spatial radiatif." Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0219.
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Les satellites placés en orbite à proximité de la Terre doivent faire face à des conditions radiatives qui dégradent fortement les matériaux qui les constituent. En orbite géostationnaire en particulier, de nombreux rayonnements électromagnétiques ou particulaires réduisent la durée de vie de ces matériaux. Les résines poly(diméthylsiloxane) sont largement utilisées sur les satellites comme adhésifs ou isolants et sont dégradées par ces rayonnements, ce qui se traduit par une perte de leur transparence et l’apparition de fissures. Les travaux présentés dans cette thèse ont pour but de limiter les dégradations subies par ces résines lorsque ces dernières sont soumises à un environnement spatial simulé, en particulier sous irradiation proton. Une première approche a été l’incorporation d’une couche de nanoparticules de silice assemblées de manière compacte à la surface des résines silicones. La taille des nanoparticules, l’épaisseur de la couche ainsi que l’ancrage covalent de ces particules à la matrice ont été étudiés. Une autre approche a été de synthétiser une résine poly(diméthylsiloxane) dont tout ou partie des noeuds de réticulation sont réversibles thermiquement, via une réaction de (rétro-)Diels-AlderSatellites on orbit near Earth have to face a radiative environment, which strongly degrades materials that constitute them. In particular, in geostationary orbit, many electromagnetic radiations and particles shorten the lifespan of such materials. Poly(dimethylsiloxane) resins are used in large amounts on satellites as binders or insulators and are degraded by these radiations, which translates into a loss of transparency and the formation of cracks at their surface. The work presented herein aims at limiting the degradations suffered by the resins when they undergo simulated ageing, especially through proton irradiation. In a first approach, the embedding of a layer of silica nanoparticles assembled in a compact way at the surface of the resins was studied. The size of the nanoparticles, their diameter, as well as their covalent binding to the matrix were investigated. A second approach was to synthetize a poly(dimethylsiloxane) resin in which all or part of the crosslinking is achieved via a thermically reversible (retro-)Diels-Alder reaction