M.Sc. (Chemistry) / Please refer to full text to view abstract

Conventional melt transesterification successfully synthesized high molecular weight segmented copolyesters.  The cycloaliphatic monomers 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO) and dimethyl-1,4-cyclohexane dicarboxylate (DMCD) afforded sterically hindered, ester carbonyls in high-Tg polyester precursors.   Reaction between the polyester polyol precursor and a primary or secondary alcohol at melt polymerization temperatures revealed reduced transesterification of the polyester hard segment as a result of enhanced steric hindrance adjacent to the ester linkages.  Subsequent polymerization of a 4,000 g/mol polyol with monomers comprising the low-Tg block yielded high molecular weight polymers that exhibited enhanced mechanical properties compared to a non-segmented copolyester control.  Atomic force microscopy uncovered unique needle-like, interconnected, microphase separated surface morphologies, and small-angle X-ray scattering confirmed the presence of bulk microphase separation. This new synthetic strategy enabled selective control of ionic charge placement into the hard segment or soft segment block of segmented copolyesters using melt transesterification.  The ionic placement impacted the microphase-separated morphology, which influenced its thermomechanical properties and resulting mechanical performance.  Melt transesterification of low-Tg, sodium sulfonated copolyesters achieved up to 15 mol% ionic content.  The 10 and 15 mol% sodium sulfonated copolyesters exhibited water-dispersibility, which enabled cation dialysis exchanges to divalent metal cations.  The sulfonated copolyesters containing divalent metal cations exhibited enhanced rubbery plateau moduli to higher temperatures.   Novel trialkylphosphonium ionic liquids chain extenders enabled the successful synthesis of poly(ethylene glycol)-based, cationic polyurethanes with pendant phosphoniums in the hard segments (HS).  Aqueous size exclusion chromatography (SEC) confirmed the charged polyurethanes, which varied the phosphonium alkyl substituent length (ethyl and butyl) and cationic HS content (25, 50, 75 mol%), achieved high absolute molecular weights.  Dynamic mechanical analysis (DMA) demonstrated the triethylphosphonium (TEP) and tributylphosphonium (TBP) polyurethanes displayed similar thermomechanical properties, including increased rubbery plateau moduli and flow temperatures.  Fourier transform infrared spectroscopy (FTIR) emphasized the significance of ion-dipole interaction on hydrogen bonding. Atomic force microscopy (AFM), small-angle X-ray scattering (SAXS), and wide-angle X-ray diffraction (WAXD) supported microphase separated morphologies in the trialkylphosphonium polyurethanes, despite the presence of ionic interactions. Sorption isotherm experiments revealed TBP polyurethanes displayed similar water sorption profiles to the noncharged analogue and lower water absorptivity compared to TEP.  The phosphonium polyurethanes displayed significantly improved tensile strain; however, lower tensile stress of the TEP polyurethane was presumably due to absorbed water.  In addition, we also explored applications of the trialkylphosphonium polyurethanes as nucleic acid delivery vectors and demonstrated their abilities to form colloidally stable polyplexes in salt-containing media. / Ph. D.

Morphological studies were carried our on thermotropic liquid crystalline copolyesters based on poly(ethyleneterephthalate) (PET) and para hydroxybenzoate (PHB), where PHB content varied from 0 mole percent up to 80 mole percent. The technique of chemical etching coupled with SEM and WAXS was utilized to obtain structural information. Morphological changes that occur when these materials are exposed to solvents such as dioxane or acetone and dye carriers were also studied using SEM. Electron microscopy results on the thermally pressed, quenched and chemically etched films indicate that selective chemical etching, i.e. etching of PET rich regions, occurs. This indicates a heterogeneous structure. An oversimplified molecular model has been proposed based on these results where at low PHB levels a PET rich phase is the continuous phase and at higher PHB levels (≥60 mole%PHB) a PHB rich phase is the continuous phase. SEM results on pressed, quenched, annealed and etched films show a "bricklike" structure similar to that seen when pure PET is chemically etched. WAXS studies show that crystallization is induced by solvent (etchant) at small etching times which indicates that the etching of PET rich regions is a two step process; (i) solvent induced crystallization, (ii) chemical etching. Dyeing studies carried out the PET/PHB systems using two different dye carriers indicate that dyeing occurs preferentially in the PET regions. Morphological studies on the dyed materials show a "puffed up" structure present only in the 50 mole% PHB material. / Master of Science

This work deals with the melt blend of 60/40 PHB/PET (p-hydroxybenzoic acid and polyethylene terephthalate) and 80/20 PHB/PET copolyesters in a 50:50 weight% ratio. Specifically, the interest was to determine as to how do the mechanical properties of the injection-molded parts from the blend compare with that of 70/30 PHB/PET composition and to find out if the melt blend obtained after a single extrusion pass represents an equilibrium composition blend. To determine the anisotropic mechanical properties, injection-molded plaques were obtained by injection-molding the blend at different temperatures. It was found that the tensile properties (tensile strength, modulus and elongation at break in the machine direction) of the blend increase with the increase in the injection-molding temperature (from 300 to 320°c) and then decrease. The flexural modulus of the injection-molded plaques (at an injection-molding temperature of 330°c) of a 50:50 blend of 60/40 PHB/PET and 80/20 PHB/PET mixed only in the injection-molded unit was 2.2 x 10⁶ psi which is 40% higher than that reported for the 60/40 PHB/PET, 100% higher than reported for either 80/20 PHB/PET or 70/30 PHB/PET. To determine the equilibrium nature of the blend, samples with different residence time in the extruder and the 70/30 PHB/PET samples were analyzed by means of Differential Scanning Calorimeter (DSC), Dynamic Mechanical Analysis (DMA), Thermal Mechanical Analysis (TMA), Scanning Electron Microscope (SEM) and Rheometrics Mechanical Spectrometer (RMS), and the mechanical properties of the injection-molded plaques were also determined. The DSC thermogram of the four extrusion pass blend showed multiple melting endotherms. Similar behavior was observed for a number of samples which had been annealed above the melt temperatures for different lengths of time. The formation of multiple peaks was attributed to the incomplete transesterification reaction in the extruder. The OMA results also indicated a substantial decrease in the melting temperatures with the increase in the number of extruder passes. A similar decrease in the melting temperatures has been reported in the literature for various polyesters undergoing transesterification reaction. The TMA results showed that the modulus versus temperature profiles (softening profiles) of one, two and three extrusion pass samples were the same but that of the four extrusion pass film was different and was closer to the softening profile of the 70/30 PHB/PET film. The softening profile of the four extrusion pass sample indicated the presence of crystallites of varying degrees of development, which corresponds well with the splitting peak phenomenon observed in the corresponding DSC thermograms. Thus, it is clear that a chemical reaction is occurring in the extruder. It is suspected that the observed decrease in the flexural properties with the increase in the number of extruder passes is due the transesterification reaction occurring in the extruder. Transesterification studies were also carried out in a cone & plate geometry in the RMS in a no-shear (simple melt annealing) and shearing environment on a larger time scale. From a comparison of the thermal behavior of the blend (as a function of the reaction time) in different environments, it was concluded that the transesterification reaction proceeds faster in the presence of deformation such as occurs in the extruder or in a simple shear flow and with an increase in temperature. Finally, to compare the rheological properties of the multiple extrusion pass and the 70/30 PHB/ PET samples, dynamic frequency sweeps were performed in the RMS at different temperatures. At a given frequency, the complex viscosity, storage modulus and loss modulus increased with an increase in the number of extrusion passes. This increase is unexpected. A number of explanations have been proposed to account for this increase in the rheological properties. / Master of Science

Poly(arylene ether)s (PAEs) were synthesized via the silyl ether displacement route. Both AA, BB, and AB silylated monomers were prepared by partial or complete hydrolysis of the dihalide using potassium hydroxide in aqueous dimethyl sulfoxide followed by silylation with hexamethyl disilazane. Both linear and star-branched structures of PAEs were synthesized and this polymerization route allowed both random and block copolymers to be prepared. Triaryl phosphine oxide containing homo-& co-PAEs exhibited very high char yields, which suggested that these polymers were potentially flame-resistant materials. The AB type halogenophenols were also polymerized in the presence of diphenylsulfone as a diluent and potassium carbonate as a base at elevated temperatures. Poly(ε-caprolactam) (Nylon 6) copolymers were prepared by the incorporation of controlled molecular weight poly(arylene ether sulfone) (PES) oligomer segments into the polymer backbone which were functionalized with carboxyl end groups. A hydrolytic melt polymerization process was used to copolymerize the oligomers with ε-caprolactam. Two series of the copolymers, with varying weight ratios and PES segment lengths, were investigated. Extensive characterization experiments including thermal analysis, mechanical property measurement, wide angle x-ray diffraction and dynamic mechanical analysis were performed to illustrate that the copolymers displayed a good balance of properties. Hydrolytically stable triaryl phosphine oxide containing dicarboxylic acid monomers were synthesized and were chemically incorporated into the poly(hexamethylene adipamide) backbone to produce improved flame-resistant copolymers. The content of triaryl phosphine oxide comonomer in the melt synthesized copolymers was controlled from 0-30 mole%. The copolymers were melt crystallizable only at 10 and 20 mole% incorporation of the phosphine oxide comonomer. Cone calorimetric tests were employed to investigate the fundamental flame retardancy behavior of the copolymers. The tests were conducted in a constant heat environment (40 kW/m²). Significantly depressed heat release rates were observed for the copolymers containing phosphine oxide moiety. The results of the cone calorimetric tests and TGA data suggested that the triaryl phosphine oxide containing nylon 6,6 copolymers had improved flame resistance properties. The triaryl phosphine oxide dicarboxylic methyl ester was also introduced into poly(ethylene terephthalate) via melt transesterification to produce copolymers which had increased char yields as the P(O) content increased. However, crystallinity was totally disrupted at 20 mole percent P(O) incorporation in compression molded specimen. Novel star-branched liquid crystalline polyarylates (LCP) were made via melt acidolysis which were subsequently transformed to liquid crystalline foams by supersaturation of carbon dioxide followed by thermal blowing. It was found that the AB type monomers were essential to generate star shaped LCPs without crosslinking. The branching agents were necessary to control the molecular weights, disrupt crystallinity and to allow for higher gas uptake by the polymer matrix. / Ph. D.

CHARLES UNIVERSITY IN PRAGUE Faculty of Pharmacy in Hradec Králové Department of Pharmaceutical technology Name of the student: Hana Jakubíková Title of diploma thesis: Aciclovir release from mucoadhesive polyester matrices Consultant: PharmDr. Eva Šnejdrová, Ph.D. The aim of this diploma thesis was to investigate aciclovir release from polyesters of lactic acid and glycolic acid branched with mannitol, pentaerythritol, dipentaerythritol and tripentaerythritol, and plasticized using ethyl pyruvate or methyl salicylate. Theoretical part sums up the application possibilities of mucoadhesive preparations. Experimental part of thesis deals with aciclovir release from polyester matrices applied on mucous substrate. Short term dissolution experiments of aciclovir were carried out in phosphate citrate buffer of pH 7, 4 at 37 řC. Mucus from porcine stomach was used as model substrate. The amount of aciclovir released was determined spectrophotometrically at 256 nm contrary to a blank sample, and also using HPLC method. Dissolution of aciclovir was affected by molar mass of polyester, and by the type and concentration of plasticizer. Polyester branched with 3 % of tripentaerythritol, and plasticizes by 40 % of methyl salicylate was found to be most suitable carrier of aciclovir for topical application on...

Afin de garantir la pérennité des ouvrages en bois, ce matériau naturellement dégradable par de nombreux organismes biologiques, doit généralement subir des traitements de protection. L'usage de produits biocides est actuellement la solution la plus employée pour conférer au bois une durabilité supplémentaire. Cependant, devant la problématique environnementale qu'ils soulèvent, l'utilisation de substances biocides est de plus en plus limitée par la réglementation. Des alternatives à l'emploi de biocides ont été développées pour augmenter la durabilité du bois : le traitement thermique et la modification chimique. Le traitement thermique consiste en la dégradation contrôlée des macromolécules du bois, pour le rendre plus hydrophobe, plus stable dimensionnellement et plus résistant à l'attaque des champignons de dégradation. Cependant ce type de traitement affaiblit les propriétés mécaniques du matériau. La modification chimique consiste en l'imprégnation de molécules au sein du matériau, lesquelles vont ensuite réagir avec les constituants du bois pour modifier sa structure chimique. Au cours de cette thèse, des traitements à base de molécules bio-sourcées ont été développés. Ainsi, les traitements opérés sur du hêtre, essence particulièrement sensible à la biodégradation et dimensionnellement instable, ont permis d'améliorer sensiblement ces propriétés. La formation in situ de polyesters de glycérol et de différents acides carboxyliques engendre un matériau plus résistant mécaniquement que les bois traités thermiquement, tout en apportant également une stabilité dimensionnelle et une durabilité renforcées. Les différents acides carboxyliques employés ont, de plus, induit des comportements différents au regard des différentes propriétés étudiées, mettant en lumière l'importance de la structure chimique des réactifs employés. Le traitement le plus prometteur a fait l'objet d'une étude économique montrant la viabilité de l'industrialisation du procédé, qui permettrait alors l'obtention d'un bois modifié utilisable en classe d'emploi 3, tout en valorisant une ressource abondante et sous-exploitée / In order to guarantee the sustainability of structure made of wood, this material, which is naturally degradable by many biological organisms, must generally undergo protection treatments. The use of biocidal products is currently the most employed solution to confer the wood additional durability. However, facing of the environmental problem they raise, their use tends to be increasingly limited by regulation. Alternatives to the use of biocides have been developed to increase the durability of wood: heat treatment and chemical modification. Heat treatment consists of the controlled degradation of wood macromolecules to make it more hydrophobic and therefore more dimensionally stable and more resistant to the attack of the fungi of degradation, but weakens its mechanical properties. Chemical modification involves the impregnation of molecules within the material, which then react with the constituents of the wood to modify its chemical structure. During this thesis, treatments based on bio-based molecules have been developed. Thus, the treatments carried out on beech, a species which is particularly sensitive to biodegradation and dimensionally unstable, have made possible to improve substantially these properties. The in situ formation of polyesters of glycerol and various carboxylic acids produces a material more resistant mechanically than thermally treated wood, while also providing enhanced dimensional stability and durability. The various carboxylic acids employed have also induced different behavior with regard to the various properties studied, highlighting the importance of the chemical structure of the reagents employed. The most promising treatment was the subject of an economic study showing the viability of the industrialization of the process, which would then make it possible to produce a modified wood that can be used in use class 3, while enhancing an abundant under-exploited resource

Certains polymères synthétiques biodégradables ont montré des propriétés physico-chimiques aussi intéressantes que celles des plastiques issus du pétrole. Cependant, leur coût élevé dû au prix des matières premières ainsi qu’au faible nombre de voies de synthèse efficaces empêchent leur rentabilité. Une des alternatives serait le développement de méthodes de production viables économiquement par l’utilisation de catalyseurs productifs et de voies de synthèses à économie d’atomes. Ce manuscrit rassemble les travaux effectués durant la thèse sur une série de catalyseurs organométalliques hautement actifs pour la synthèse du poly(lactide), de nouvelles stratégies catalytiques pour la production du poly(3-hydroxybutyrate) et la polymérisation à économie d’atomes d’α-aminoacide-N-carboxyanhydrides pour la production de poly(α-peptides). / Many synthetic biodegradable polymers show competitive physical properties compared to petrochemically derived plastics. However, due to the low availability and high cost of renewable feed stocks or lack of efficient synthetic routes, their industrial production and successful commercial execution lacks economical feasibility. One way to improve the current situation is the implementation of cost efficient methods either by using productive catalysts or by atom-efficient synthetic methods. Here we report the discovery of a series of highly active organometallic catalysts for the synthesis of poly(lactide), new catalytic methodologies for the production of poly(3-hydroxybutyrate), and an atom-efficient polymerization of α-aminoacid-N-carboxyanhydrides to poly(α-peptides).

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La photopolymérisation est un procédé en plein essor qui permet d’accéder à des matériaux polymères, notamment sous la forme de films ou de revêtements. Néanmoins, celle-ci est majoritairement basée sur un mécanisme de polymérisation radicalaire qui proscrit l’obtention de matériaux totalement biodégradables. Aussi, au cours de cette thèse, nous nous sommes intéressés à la photopolymérisation par ouverture de cycle (photoROP) d’esters et de carbonates cycliques à l’aide de deux grandes familles de photogénérateurs de bases (PBGs). Tout d’abord, des PBGs, pouvant libérer des superbases de type amidine et guanidine cycliques ont été employées pour mener efficacement la photoROP du L-LA et du TMC en solution. Puis, nous nous sommes attachés à développer, sur le modèle des photobases précédentes, de nouveaux PBGs qui libèrent sous irradiation UV des carbènes N-hétérocycliques (NHCs). La libération des NHCs à partir de ces « NHCs photolatents » a été prouvée par RMN 1H et par la formation d’adduits NHC.CS2. De même, ces PBGs se sont révélés actifs pour la photoROP du L-LA et du TMC en solution, mais avec une plus faible efficacité que les PBGs précédents. En effet, les cinétiques de polymérisation sont lentes du fait de la présence de CO2 dans le milieu (libéré lors de l’irradiation UV) qui conduit à la formation d’adduit NHC.CO2 inactif en ROP. Ainsi, la photobase la plus performante, libérant du TBD, a été employée afin d’effectuer la photoROP en masse d’esters cycliques liquides (ε-CL, δ-VL et un mélange innovant L-LA/TMC). Finalement, des réseaux ont été formés par incorporation dans le milieu réactionnel d’un monomère bifonctionnel, permettant d’obtenir sur demande (contrôle temporel) des matériaux réticulés potentiellement entièrement biodégradables. / Photopolymerization is a growing process allowing preparing polymer materials, notably in the form of films or coatings. Nevertheless, it is mostly based on a radical polymerization mechanism that prevents obtaining fully biodegradable materials. The goal of this PhD work was thus to develop the photopolymerization of cyclic esters and carbonates by using two families of photobase generators (PBGs). First, already described PBGs, releasing cyclic amidine and guanidine-type superbases, were effectively employed to carry out the photopolymerization of L-LA and TMC in solution. Then, taking previous PBGs as models, we developed new PBGs able to release N-heterocyclic carbenes (NHCs) under UV irradiation. The release of NHCs from these “photolatent NHCs” was proven both by 1H NMR and by the formation of NHC.CS2 adducts. These PBGs also proved to be active for the ROP of L-LA and TMC in solution, but to a lesser extent than previous photobases. Indeed, slower kinetics of polymerization were observed, which was attributed to the presence of CO2 in the reaction medium (CO2 released by photodegradation of the PBG) that leads to the formation of NHC.CO2 adduct (inactive for ROP). Thus, the most efficient photobase (releasing TBD) was employed to carry out the bulk photopolymerizations of liquid cyclic esters (ε-CL, δ-VL and even an innovative L-LA / TMC mixture). Finally, polymer networks have been formed by incorporating a bifunctional monomer into the reaction medium, allowing the preparation “on demand” (temporal control) of potentially fully biodegradable materials in a one-pot process.