Dissertations / Theses on the topic 'Multi-functional Polymers'

Amphiphilic block and graft copolymers have been studied because of the possibility of tailoring their complex and fascinating chemical properties. Potential applications include wetting agents, foaming agents, plastic modifiers as well as biomedical applications in drug delivery, owing to their biocompatible and low toxic nature. This thesis describes the study of a series of amphiphilic block copolymers, known as Pluronics, and their aqueous interaction with a hydrophobic drug, flurbiprofen. Synthesis and characterisation of novel graft copolymers with interesting associative behaviour that is less influenced by concentration is also another major aspect of the work described in this thesis. Pulsed-field gradient stimulated-echo nuclear magnetic resonance (pFGSE- NMR) and surface tension measurements have been used to show that the addition of flurbiprofen promotes micellisation of Pluronic triblock copolymers (PI03, P123, and L43). Structural changes in the micelles ofPluronics PI03 and P123, as a function of temperature, eo-solvent (ethanol, 10 wt/vol %), and the addition of the hydrophobic drug flurbiprofen were also investigated by small- angle neutron scattering (SANS). Flurbiprofen was shown to be released from micelles by increasing the solution pH. At higher pH, the drug is ionised and the fraction of polymer in micelles reduces. Synthesis of novel graft copolymers was carried out using a "grafting onto" method. In this approach, the functional group of a hydrophobic backbone will react with the functional group of the copolymer chains. The graft copolymers composed of either hydrophilic Pluronics or sulfonated poly(ethylene oxide) chains and hydrophobic backbones, displayed formation of core-shell micelles in selective solvents. The Pluronic graft copolymers showed the potential for solubilising hydrophobic drug molecules in aqueous solution even at low polymer concentrations. These graft copolymers and their interactions with flurbiprofen were characterised by PFGSE-NMR and SANS.

Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009.
Committee Chair: Weck, Marcus; Committee Member: Breedveld, Victor; Committee Member: Bunz, Uwe; Committee Member: Liotta, Charles; Committee Member: Marder, Seth; Committee Member: Srinivasarao, Mohan. Part of the SMARTech Electronic Thesis and Dissertation Collection.

This thesis demonstrates a comprehensive study of multifunctional applications of low-cost solution-processable organic semiconducting materials. It presents a series of rationally designed predominantly dye based innovative soft semiconductors with their generic optoelectronic properties. The performance of these materials’ application in various devices, including transistors, solar cells, memory devices and displays, are evaluated through world class collaboration to establish the structure-property relationship. In doing so, we not only developed several high-performance materials but also found that fused ring incorporation into the conjugated backbone is an effective strategy to construct multifunctional semiconductors towards flexible and printed electronics.

Magnetoelectric (ME) interactions in matter correspond to the appearance of magnetization by means of an electric field (direct effect) or the appearance of electric polarization by means of a magnetic field (converse effect). The composite laminates which possess large ME coefficient, have attracted much attention in the field of sensors, modulators, switches and phase inverters. In this thesis, we report on the ME performances of the bi- and tri- layered composites. It is shown that their ME couplings can be achieved by combining magnetostrictive and piezoelectric layers. A model based on a driven damped oscillation is established for the piezoelectric/magnetostrictive laminated composite. It is used to simulate the mechanical coupling between the two layers. In addition, we report that the ME coupling can be achieved without magnetic phase but only with eddy current induced Lorentz forces in the metal electrodes of a piezoelectric material induced by ac magnetic field. The models based on the Lorentz effect inducing ME coupling in PZT unimorph bender, polyvinylidene fluoride (PVDF) film and PZT ceramic disc are thus established. The results show the good sensitivity and linear ME response versus dc magnetic field change. Thus, the room temperature magnetic field detection is achievable using the product property between magnetic forces and piezoelectricity. Besides, we report on the electrostrictive performance of cellular polypropylene electret after high-voltage corona poling. We use the Surface Potential test, Thermal Stimulated Depolarization Current experiment and Differential Scanning Calorimetry experiment to analyse its charge storage mechanism. The result show that the electrostrictive coefficient and relative permittivity of the charged samples increase. Last but not least, in order to explain this phenomenon, a mathematic model based on the charged sample has been established.

2012/2013
Materiali e rivestimenti nanostrutturati possono potenzialmente apportare significativi cambiante nel campo della nanoscienze, nonché offrire una nuova generazione di materiali con caratteristiche e performance migliori. A questo proposito le tecniche computazionali diventano uno strumento fondamentale, in grado di ridurre notevolmente i tempi che vanno dall’idea iniziale al prodotto finito. La simulazione molecolare permette infatti la previsione delle proprietà macroscopiche prima che i materiali vengano preparati e caratterizzati sperimentalmente; consente inoltre una migliore comprensione dei fenomeni fisici su scala nanometrica. In questo lavoro di tesi sono presentati alcuni casi studio in cui vengono proposte diverse procedure computazionali per affrontare importanti aspetti come la bagnabilità della superficie, l’effetto della dimensione e della forma delle nanoparticelle e i loro meccanismi di aggregazione/dispersione. In questo contesto, si è dimostrata la vasta applicabilità della modellazione molecolare evidenziando quindi come questa rappresenti un potente strumento per comprendere e controllare le proprietà finali di materiali nanostrutturati, aprendo così la strada ad una progettazione in silico di nuovi materiali.
Nanostructured materials and coatings have the potential to change materials science significantly, as well as to provide a new generation of materials with a quantum improvement in properties. In this regard computational materials science becomes a powerful tool. It is able to rapidly reduce the time from concept to end product. Molecular simulation enables the prediction of properties of these new materials before preparation, processing, and experimental characterization, as well as a better understanding of the physical phenomena at the nanoscale level. In this thesis we present several study cases in which we propose different computational recipes to deal with different important topics such as surface wettability, effect of nanoparticles size and shape and nanoparticles aggregation/dispersion. In this context, we demonstrate the broad applicability of the molecular modelling and we ascertain that molecular simulation represent a powerful tool to understand and control the nanomaterials properties thus opening avenues for the in silico design of new materials.
XXVI Ciclo
1985

Förfrågan efter nya och mer avancerade applikationer är en pågående process vilket leder till en konstant utveckling av nya material. För att förstå relationen mellan en applikations egenskaper och dess sammansättning krävs full förståelse och kontroll över materialets uppbyggnad. En sådan kontroll över uppbyggnaden hos material hittas i en undergrupp till dendritiska polymerer som kallas dendrimerer. I den här doktorsavhandlingen belyses nya metoder för att framställa dendrimer med hjälp av selektiva kemiska reaktioner. Sådana selektiva reaktioner kan hittas inom konceptet klickkemi och har i detta arbete kombinerats med traditionell anhydrid- och karbodiimidmedierad kemi. Denna avhandling diskuterar en accelererad tillväxtmetod, dendrimerer med inre och yttre reaktiva grupper, simultana reaktioner och applikationer baserade på dessa dendritiska material. En accelererad tillväxtmetod har utvecklats baserad på AB2- och CD2-monomerer. Dessa monomerer tillåter tillväxt av dendrimerer utan att använda sig av skyddsgruppkemi eller aktivering av ändgrupper. Detta gjordes genom att kombinera kemoselektiviteten hos klickkemi tillsammans med traditionell syraklorid kopplingar. Dendrimerer med inre alkyn- eller azidfunktionalitet syntetiserades genom att använda AB2C-monomerer. Den dendritiska tillväxten skedde med hjälp av karbodiimidmedierad kemi. Monomererna som användes bär på en C-funktionalitet, alkyn eller azid, och på så sätt byggs får interiören i de syntetiserade dendrimeren en inneburen aktiv funktionell grupp. Ortogonaliteten hos klickkemi användes för att sammanfoga monomerer till en dendritisk struktur. Traditionell anhydridkemi- och klickemireaktioner utfördes samtidigt och på så sätt kunde dendritiska strukturer erhållas med färre antal uppreningssteg. En ljusemitterande dendrimer syntetiserades genom att koppla azidfunktionella dendroner till en alkynfunktionell cyclenkärna. Europiumjoner inkorporerades i kärnan varpå dendrimerens fotofysiska egenskaper analyserades. Mätningarna visade att den bildade triazolen hade en sensibiliserande effekt på europiumjonen. Termiska studier på några av de syntetiserade dendrimerer utfördes för att se om några av dem kunde fungera som templat vid framställning av isoporösa filmer.
The need for new improved materials in cutting edge applications is constantly inspiring researchers to developing novel advanced macromolecular structures. A research area within advanced and complex macromolecular structures is dendrimers and their synthesis. Dendrimers consist of highly dense and branched structures that have promising properties suitable for biomedical and electrical applications and as templating materials. Dendrimers provide full control over the structure and property relationship since they are synthesized with unprecedented control over each reaction step. In this doctoral thesis, new methodologies for dendrimer synthesis are based on the concept of click chemistry in combination with traditional chemical reactions for dendrimer synthesis. This thesis discusses an accelerated growth approach, dendrimers with internal functionality, concurrent reactions and their applications. An accelerated growth approach for dendrimers was developed based on AB2- and CD2-monomers. These allow dendritic growth without the use of activation or deprotection of the peripheral end-groups. This was achieved by combining the chemoselective nature of click chemistry and traditional acid chloride reactions. Dendrimers with internal azide/alkyne functionality were prepared by adding AB2C monomers to a multifunctional core. Dendritic growth was obtained by employing carbodiimide mediated chemistry. The monomers carry a pendant C-functionality (alkyne or azide) that remains available in the dendritic interior resulting in dendrimers with internal and peripheral functionalities. The orthogonal nature of click chemistry was utilized for the simultaneous assembly of monomers into dendritic structures. Traditional anhydride chemistry and click chemistry were carried out concurrently to obtain dendritic structures. This procedure allows synthesis of dendritic structures using fewer purification steps. Thermal analyses on selected dendrimers were carried out to verify their use as templates for the formation of honeycomb membranes. Additionally, a light emitting dendrimer was prepared by coupling of azide functional dendrons to an alkyne functional cyclen core. A Europium ion was incorporated into the dendrimer core, and photophysical measurements on the metal containing dendrimer revealed that the formed triazole linkage possesses a sensitizing effect.
QC 20100629

The discovery of novel and efficient stimuli-responsive materials that change their properties according to external stimuli and therefore, adjust to our demands become an interesting research topic for several potential applications. The integration of the most promissory stimuli-responsive materials in devices for antiglare car mirrors, smart windows, sunglasses, sensors, among others has been applied. In this thesis, the development and application of stimuli-responsive materials containing ionic photochromic or electrochromic units have been explored. In general, it is possible to incorporate specific scaffolds possessing pH, temperature, and light or electron-transfer stimuli-responsive behaviour in the cation or anion structures. Also, ionic polymers based on these structures have been investigated. In this context, 4,4’-bipyridinium, diarylethenes and flavylium were selected as electrochromic and photochromic units, respectively. For the preparation of the selected organic salts including polymers, different synthetic routes and purification processes have been followed. Detailed characterization of all prepared salts by spectroscopic techniques in order to elucidate their structures and purities has been performed. Thermal, rheological, photochemical and electrochemical properties of some prepared salts were also studied. It is important to focus that the adequate selection of the counter-ions can be crucial to achieve ionic liquids as well as to tune their final properties. The most promissory electrochromic salts based on 4,4’-bipyridinium symmetrical and non-symmetrical di and tetra-cations as well as ionic polymers were tested in liquid, gel or solid electrochromic devices. The substituents from bipyridinium scaffold as well as counter-ions can significantly influence the electrochromic performance in particular its reversibility; stability; colour contrast and transition times. Photochromic Room Temperature Ionic Liquid based on the combination of diarylethene derivative anion with tri-octyl methylammonium ([ALIQUAT]) cation was developed and characterized. Additionally, a new thermal, pH and photo-stimuli responsive co-polymer containing N-isopropylacrylamide and flavylium derivative have been prepared. The chemical versatility of the prepared ionic photo- and electrochromic materials opens excellent perspectives for future applications as efficient and reversible multi stimuli-responsive materials.

Applications of nanotechnology in medicine, also known as nanomedicine, is a rapidly growing field as it holds great potential in the development of novel therapeutics toward treatment of various diseases. Shell crosslinked knedel-like nanoparticles (SCKs) that are self assembled from amphiphilic block copolymers into polymeric micelles followed by crosslinking selectively throughout the shell domain have been investigated as theranostic agents for the delivery of nucleic acids and incorporation of imaging probes. The main focus of this dissertation is to design and develop unique multifunctional bio-synthetic hybrid nanoparticles that can carry agents for radiolabeling, moieties for inducing stealth properties to minimize protein adsorption in vivo, ligands for site-specific targeting, therapeutic payloads, and are optimized for efficient delivery of cargoes intracellularly and to the target sites toward constructing novel nanoscopic objects for therapy and diagnosis. Alteration of polymeric building blocks of the nanoparticles provides opportunities for precise control over the sizes, shapes, compositions, structures and properties of the nanoparticles. To ensure ideal performance of nanoparticles as theranostic agents, it is critical to ensure high intracellular bioavailability of the therapeutic payload conjugated to nanoparticles. Special efforts were made by employing well-defined multi-step polymerization and polymer modification reactions that involved conjugation of peptide nucleic acids (PNAs) to chain terminus of poly(ethylene glycol) (PEG) chain grafts such that they were presented at the outermost surface of SCKs. Additionally, chemical modification reactions were performed on the polymer backbone to integrate positive charges onto the shell of the nanoparticles to afford cationic SCKs (cSCKs) for facilitating cellular entry and electrostatic interactions with negatively charged nucleic acids. Covalent conjugation of F3, a tumor homing peptide, post-assembly of the nanoparticles enhanced cellular uptake and knockdown of nucleolin (a shuttling protein overexpressed at the sites of angiogenesis) and thus inhibiting tumor cell growth. Furthermore, these polymer precursors of the cSCKs were modified with partial to full incorporation of histamines to facilitate their endosomal escape for efficient delivery into the cytosol. The cSCKs were further templated onto high aspect ratio anionic cylinders to form hierarchically-assembled nanostructures that bring together individual components with unique functions, such as one carrying a therapeutic payload and the other with sites for radiolabeling. These higher order nanoobjects enhance circulation in vivo, have capabilities to package nucleic acids electrostatically and contain sites for radiolabeling, providing an overall advantage over the individual components, which could each facilitate only one or the other of the combined functions. Hierarchically-assembled nanostructures were investigated for their cellular uptake, transfection behavior and radiolabeling efficiency, as the next generation of theranostic agents.

碩士
國立臺北科技大學
化學工程研究所
98
PART I We want to synthesis the multiple-functional photosensitive polymer to enhance the polymer`s mechanical strength。In the exposure test，we hope that polymer`s crosslinking were excellently，so we could find out in the IR spectrum，in the 2260 cm-1，the peak has goned。It`s reveal`s tht –N=C=O peak has been reaction with the –C=O bond。 Also we can find out the GPC spectrum reveal1s that there were some biproducts in the spectrum，it must be reaction not fully。But from the exposure test，we can see that the line patern are clearly，and not brokend。So we say that the synthesis was succesful。 PART II Polymer electrolyte (PE)，which were synthesized based on polyurethane 、isophporne diisocyanate (IPDI) and 1,4-butanediol (1,4 BDO)，were used as the matrices of solid polymer electrolytes based on lithium perchlorate ( LiClO4 ) in this study. Study on the polymer structure to the conductivity and mophology。The research has pointed out the conductivity dependented on the soft segement concentraction、crystallinity、and phase seperation。The results appearanced that PE has conductivity 4.937×103 S/cm in the room temperature。 Furthermore，we added the poly(hexane-1,6-diyl carbonate) diol (PHCD) as the soft segment in the PU polymer and discussed the lithium ion`s solvation。And discuss the salvation of polymer by FT-IR spectrum，also discusing the conductivity ability by AC-Impedance。From the FT-IR，we can know the-N-H group`s absorbance peak at 3440cm-1，increasing the Li+concentration the –N-H group`s peak will move from low wavenumber to high wavenumber。The result reveals that addition the Li+ will action with –N-H group to result in bond length shortly and wavenumber increase。Then we use the PHCD to reduce the crstallinity and the phase seperation。From the DSC graph，we know the Tg point reduce from -54 to -57℃。And from the conductivity test can know Tg point reduce，the conductivity will increase。 Finally，we preparation the composite SPE base on the PVDF/HFP。We preparation the porous membrane of PVDF/HFP to enhace the absorption of PU-base electrolyte。From the SEM graphs can found the method of preparation membrane with porous are succesuly，and from the conductivity tests can obtain the conductivity 6.3×10-5 in the room temperature。

碩士
國立成功大學
化學系碩博士班
93
Abstract 　Mesoporous silicas and carbons have been applied in various areas, including gas separation, water purification, catalyst support, and electrode material for electrochemical devices. 　In this thesis, there are two major researching parts. A convenient synthetic of mesoporous carbons and silica is still desired. In the first part, we focused on the synthesis of SBA-16 mesoporous silicas of cubic Im3m structure with Pluronic F127 (EO106PO70EO106) as template. To explore the effects of various reaction factors on the mesostructure orderness of the SBA-16, we adjusted pH value, aging time and hydrothermal treatment in water or mother solution. The mesoporous carbons have been efficiently prepared via a convenient impregnation method using with calcined mesoporous silica materials (SBA-16) as nanotemplates and commercial-grade phenol-formaldehyde resin as carbon source. 　In the second part of our studies, we proposed a new method to prepare the mesoporous silicas and carbons by using a polymer blend of neutral polymer and phenol-formaldehyde resin as template. Through a rapid silification, a neutral polymer—PF resin—silica composites was generated. After calcination for removing organics, the mesoporous silicas were obtained with surface areas ( 300—700 m2g-1) and pore sizes ( 2.0—11.0 nm). On the other hand, neutral polymer—PF resin—silica composites can be converted to mesoporous carbons via a consequent processes of polymerization at 100 oC, pyrolysis under N2 atmosphere at 1000 oC and HF-etching . The mesoporous carbons possess the properties of high surface areas ( 700—1900 m2g-1), large pore volume ( 0.3—1.1 cm3g-1). In order to explore the effects of reaction factors on the mesostructured materials, we adjusted pH value, water content, PF resin/neutral polymer ratio and hydrothermal treatment. When physical and chemical properties of mesoporous carbons and silicas can be easily manipulated, exceptional application in adsorbent for large molecules, hard-template of metal oxides, electrode materials of methanol fuel cell, and electrochemical double layers capacitor will be further explored.

Materials with appropriate combinations of multifunctional properties (strength, toughness, electrical conductivity and piezoelectricity) together with desired biocompatibility are promising candidates for biomedical applications. Apart from these material properties, recent studies have shown the efficacy of electric field in altering cell functionality in order to elicit various cell responses, like proliferation, differentiation, apoptosis (programmed cell death) on conducting substrates in vitro. In the above perspective, the current work demonstrates how CaTiO3 (CT) addition to Hydroxyapatite (HA) can be utilised to obtain an attractive combination of long crack fracture toughness (up to 1.7 MPa.m1/2 measured using single edge V-notch beam technique) and a flexural strength of 155 MPa in addition to moderate electrical conductivity. The enhancement of fracture toughness in HA-CT composites has been explained based on the extensive characterization of twinned microstructure in CT along with the use of theoretical models for predicting the enhancement of toughening through crack tip tilt and twist mechanisms. Subsequent in vitro studies on HA-CT composites with human Mesenchymal Stem cells (hMSCs) in the presence of electric field has shown enhanced differentiation towards bone like cells (osteogenic lineage) as evaluated by ALP activity, Collagen content and gene expression analyses through Polymerase Chain Reaction (PCR) at the end of two weeks. he extracellular matrix mineralization analysis at the end of 4 weeks of hMSC culture further substantiated the efficacy of electric field as a biochemical cue that can influence the stem cell fate processes on conducting substrates. The electric field stimulation strategy was also implemented in in vitro studies with C2C12 mouse myoblast (muscle) cells on elastically compliant poly(vinylidene difluoride) (PVDF)-multiwall carbon nanotube (MWNT) composite substrates. PVDF is a piezoelectric polymer and the addition of MWNTs makes the composite electrically conducting. Upon, electric field stimulation of C2C12 mouse myoblast cells on these composites, has been observed that in a narrow window of electric field parameters, the cell viability was enhanced along with excellent cell alignment and cell-cell contact indicating a potential application of PVDF-based materials in the muscle cell regeneration. In an effort to rationalise such experimental observations, a theoretical model is proposed to explain the development of bioelectric stress field induced cell shape stability and deformation. A single cell is modelled as a double layered membrane separating the culture medium and the cytoplasm with different dielectric properties. This system is linearized by invoking Debye-Huckel approximation of the Poisson-Boltzmann equation. With appropriate boundary conditions, the system is solved to obtain intracellular and extracellular Maxwell stress as a function of multiple parameters like cell size, intracellular and extracellular permittivity and electric field strength. Based on the stresses, we predict shape changes of cell membrane by approximating the deformation amplitude under the influence of electric field. Apart from this, the shear stress on the membrane has been used to determine the critical electric field required to induce membrane breakdown. The analysis is conducted for a cell in suspension/on a conducting substrate and on an insulating substrate to illustrate the effect of substrate properties on cell response under the influence of external electric field.

Materials with appropriate combinations of multifunctional properties (strength, toughness, electrical conductivity and piezoelectricity) together with desired biocompatibility are promising candidates for biomedical applications. Apart from these material properties, recent studies have shown the efficacy of electric field in altering cell functionality in order to elicit various cell responses, like proliferation, differentiation, apoptosis (programmed cell death) on conducting substrates in vitro. In the above perspective, the current work demonstrates how CaTiO3 (CT) addition to Hydroxyapatite (HA) can be utilised to obtain an attractive combination of long crack fracture toughness (up to 1.7 MPa.m1/2 measured using single edge V-notch beam technique) and a flexural strength of 155 MPa in addition to moderate electrical conductivity. The enhancement of fracture toughness in HA-CT composites has been explained based on the extensive characterization of twinned microstructure in CT along with the use of theoretical models for predicting the enhancement of toughening through crack tip tilt and twist mechanisms. Subsequent in vitro studies on HA-CT composites with human Mesenchymal Stem cells (hMSCs) in the presence of electric field has shown enhanced differentiation towards bone like cells (osteogenic lineage) as evaluated by ALP activity, Collagen content and gene expression analyses through Polymerase Chain Reaction (PCR) at the end of two weeks. he extracellular matrix mineralization analysis at the end of 4 weeks of hMSC culture further substantiated the efficacy of electric field as a biochemical cue that can influence the stem cell fate processes on conducting substrates. The electric field stimulation strategy was also implemented in in vitro studies with C2C12 mouse myoblast (muscle) cells on elastically compliant poly(vinylidene difluoride) (PVDF)-multiwall carbon nanotube (MWNT) composite substrates. PVDF is a piezoelectric polymer and the addition of MWNTs makes the composite electrically conducting. Upon, electric field stimulation of C2C12 mouse myoblast cells on these composites, has been observed that in a narrow window of electric field parameters, the cell viability was enhanced along with excellent cell alignment and cell-cell contact indicating a potential application of PVDF-based materials in the muscle cell regeneration. In an effort to rationalise such experimental observations, a theoretical model is proposed to explain the development of bioelectric stress field induced cell shape stability and deformation. A single cell is modelled as a double layered membrane separating the culture medium and the cytoplasm with different dielectric properties. This system is linearized by invoking Debye-Huckel approximation of the Poisson-Boltzmann equation. With appropriate boundary conditions, the system is solved to obtain intracellular and extracellular Maxwell stress as a function of multiple parameters like cell size, intracellular and extracellular permittivity and electric field strength. Based on the stresses, we predict shape changes of cell membrane by approximating the deformation amplitude under the influence of electric field. Apart from this, the shear stress on the membrane has been used to determine the critical electric field required to induce membrane breakdown. The analysis is conducted for a cell in suspension/on a conducting substrate and on an insulating substrate to illustrate the effect of substrate properties on cell response under the influence of external electric field.