Three series copolyesters [poly(butylene succinate-co-propylene succinate) (PBPSu), poly(butylene succinate-co-2-methyl-1,3-propylene succinate) (PBMPSu) and poly(ethylene succinate-co-butylene succinate) (PEBSu)] and their homopolyesters [poly(butylene succinate) (PBSu), poly(ethylene succinate) (PESu), poly(propylene succinate) (PPSu) and poly(2-methyl-1,3-propylene succinate) (PMPSu)] were synthesized by a two-step reaction (esterification and polycondensation) with titanium tetraisopropoxide as the catalyst. Molecular weights of all synthesized polyesters were determined by intrinsic viscosity and gel permeation chromatography (GPC) measurements. The values of intrinsic viscosity (0.97 ~ 1.62 dL/g) and relative molecular weight (2.4x10000 ~ 11.9x10000 g/mol) indicate that these polyesters can be made into films without complications. Compositions and sequence distributions of copolyesters were determined by analyzing the spectra of 1H NMR and 13C NMR. The randomness values of these copolyesters are closed to 1.0 that represents random sequence distribution of the comonomers. Thermal properties and stabilities were characterized using differential scanning calorimeter (DSC) and thermogravimetric analyzer (TGA), respectively. All copolyesters exhibited a single glass transition temperature (Tg). For PBPSu copolyesters, incorporating propylene succinate units to PBSu not only narrows the window between Tg and melting temperature (Tm), but also retards the cold crystallization ability, thereby lowering the crystallinity to a considerable extent. This phenomenon also occurred in PBMPSu and PEBSu copolyesters when the 2-methyl-1,3-propylene succinate (MPS) and butylene succinate (BS) units were incorporated into PBSu and PESu, respectively. Tstart is the temperature of first detectable deviation from the derivative curve of weight loss. Tstarts of all synthesized polyesters around 240 £jC, higher than the temperature of polycondensation reaction (220 £jC), demonstrates that there is no necessity of using a thermal stabilizer during the synthesis of these polyesters. Additionally, the thermal stability does not vary significantly with compositions in the same series polyester. Wide-angle X-ray diffractograms (WAXDs) at room temperature were obtained from polyesters crystallized isothermally at a temperature around 5-20 £jC below their melting temperatures. WAXD patterns of two series polyesters elucidated that the incorporation of PS or MPS units into PBSu markedly inhibits the crystallization behavior of PBSu. The phenomenon also occurred in PEBSu copolyesters when BS units were incorporated into PESu. Results of WAXD and DSC measurements showed that PMPSu is a amorphous polyester. The retarding effect on crystallization by methyl substituents on the polymer chain is efficient.

In recent years,the recycling of plastic waste incerased worldwide.The basic impetus for this increase is the public awereness regarding polltuion of the environment.Many different types of recycling processes are being used to reduce the use of raw materials and to reduce energy consumption.PET recycling is one of the most important recycling processes.addition of thermotropic liquid crystalline polymers has also become wide-spread in recent years to increase their mechanical properties and other selected properties.In this study,it is aimed to obtai a continous or discontinous fiber from the termotropic liquid crystalline copolyester and recycled PET blend.In this study X7G was used as a copolyester.In the polymer mixtures small amounts of liquid crystalline plymer phase resulted in significantr improvements in the mechanical properties of the fibers produced in the study.The blending method used gave an alost homogeneous poymer mixture which was unexpected tat needs further study to elaborate.The preliminary DSC,SEM, tensile testing and intrinsic viscosity measurements support this conclusion.The material obtained approached to fiber grade PET in terms of fiber forming properties which therefore can be used as a second grade fiber material.

No description available.

Polyesters are an important class of polymers in many applications ranging from common-use objects—such as packaging containers, clothing, and upholstery—to more advanced applications, such as lightweight strength materials in construction, electronics, and automotive parts. Poly(ethylene terephthalate) (PET), a semicrystalline aromatic polyester, is commercially the most common and widely used polyester. However, the inability to reuse polyesters such as PET over multiple reprocessing cycles in the same application remains a challenge due to the susceptibility of the polymer to thermal, hydrolytic, and oxidative degradation during melt processing. The various degradation modes result in a drop in molecular weight, loss of key physical properties, and release of volatile compounds. Furthermore, the vast issue of plastic accumulation and pollution in diverse ecosystems, landfills, and waste streams underscores the burgeoning need to create a closed loop—responsible materials management from the cradle to the grave—through these materials' continual reuse and recycling. Additionally, most feedstock monomers used in polyester synthesis primarily come from fossil fuels. Fossil fuel extraction processes release gases and particulate matter that adversely affect health, climate, and the environment, so finding alternative sources for polyester monomers is paramount. This dissertation addresses key polyester challenges by designing and synthesizing alicyclic polyesters. First, we synthesized a series of alicyclic polyesters using various ratios of two regioisomers of a previously unexplored alicyclic monomer, bicyclohexyldimethanol (BCD). We learned from this alicyclic polyester series that we could tailor properties such as morphology and elongation while raising the glass transition temperatures (Tg) and lower melting temperatures (Tm) of the polymers based on the regioisomer composition. Furthermore, the regioisomer that led to polymers with semicrystalline morphologies inspired us to apply it to PET as a copolymer, with the goal of increasing PET's stability under melt processing conditions by lowering Tm. Next, we synthesized a series of alicyclic copolyesters with different BCD compositions in the polymer. The results showed that the presence of the alicyclic rings of BCD lowers the melting temperature and enhances the stability of the polymer in the melt compared to PET. These results directed us toward synergistically combining the benefits of alicyclic monomers with sustainable biobased monomers to enhance polyester properties, thereby decoupling fossil fuels from polymer feedstock production. Accordingly, we explored naturally ubiquitous, structurally diverse, and chemically modifiable terpenes present in the resin exudate of conifers. Specifically, we derived alicyclic diacid and diol monomers from the terpene verbenone and used them to synthesize a series of biobased alicyclic polyesters. The polymer series exhibited a range of morphologies, Tg's, as well as enhanced stabilities. The semicrystalline composition exhibited higher Tg and slightly lower Tm than PET while possessing exceptional stability in the melt over PET. / Doctor of Philosophy / Polyesters are important materials widely used today. They are very large molecules composed of a basic chemical unit linked together in a repeating fashion to make a long chain. The nature of the links between the basic units is referred to as an ester link, and materials are described as polyester when the number of these links is large. The applications of polyesters range from common-use objects—such as packaging containers, clothing, and upholstery—to more advanced applications in construction, transportation, and defense—such as body armor, seat belts, and lightweight strength materials and coatings in construction. The properties of its basic structural unit enable the wide breadth of applications of polyesters. A significant challenge that faces polyesters is the inability to reuse the material in the same application multiple times. The material must be reprocessed by melting at high temperatures to be reused. This melting breaks down the polyester chain, weakening the material and rendering it unsuitable for continued use. The need to reuse polyesters is an important area of concern because of the growing problem of plastic accumulation and pollution in diverse ecosystems and landfills. If these materials are continually reused, they will not accumulate as environmental waste. Furthermore, the basic starting unit that makes up polyesters largely comes from fossil fuels. Fossil fuel extraction processes release gases and particulate matter that adversely affect health, climate, and the environment. The issues of polyester breakdown in the melt and fossil fuel use to make the polyester can be addressed in two ways. First, reinforcing the polyester through changes to the basic structural unit can prevent the breakdown of the material when melted, thereby enabling its reuse over multiple cycles. Second, reducing the dependence on fossil fuels to make the basic structural unit of the polyester can be accomplished by using more renewable biobased sources instead. This dissertation seeks to address these two challenges. In the first approach, we investigate the effect of using a special cyclic structure in the polyester make-up to reinforce its stability when melted and enable its reuse. Next, we use plant materials to derive these unique structures to reduce the dependence on fossil fuels and mitigate the environmental, climate, and health effects of fossil fuel use.

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No description available.

A series of random and amorphous copolyesters containing different cycloaliphatic rings within the polymer chains were prepared by melt polycondensaton of difunctional monomers (diesters and diols) in the presence of a catalyst. These polyesters were characterized by nuclear magnetic resonance (NMR), size exclusion chromatography (SEC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), tensile tests and/or dynamic mechanical analysis (DMA). The copolyester based on dimethyl bicyclo[2.2.2]octane-1,4-dicarboxylate (DMCD-2) was observed to have a higher Tg, about 115ºC, than the other copolyesters with the same compositions in this study. For copolyesters containing different compositions of dimethyl-1,4-cyclohexane dicarboxylate (DMCD) and DMCD-2, the Tg increased linearly with the increase of DMCD-2 mole content. DMA showed that all of the cycloaliphatic copolyesters had secondary relaxations, resulting from conformational transitions of the cyclohexylene rings. The polyester based on DMCD-3 in the hydrolytic tests underwent the fastest hydrolytic degradation among these samples. A new triptycene diol (TD) was synthesized and incorporated into a series of cycloaliphatic copolyester backbones by melt condensation polymerization. Straight chain aliphatic spacers, including ethylene glycol (EG), 1,4-butanediol (BD) and 1,6-hexanediol (HD), were used as co-diols to explore their effects on polyester properties. An analogous series of non-triptycene copolyesters based on various hydroxyethylated bisphenols were also prepared for comparison. The results revealed that the TD-containing polymers had higher thermal stability and higher Tg's than the corresponding non-TD analogs. For TD-containing copolyesters, the mechanical properties were found to be dependent on the types and compositions of the co-diols. A 1,4-butanediol-based triptycene copolyester was observed to have a significantly increased Tg and modulus while maintaining high elongation at ambient temperature. Furthermore, it was demonstrated that the triptycene polyester exhibited higher Tg and modulus than those containing bisphenol derivatives. However, all of the 1,4-butanediol based copolyesters were brittle and had comparable moduli at low temperatures (-25°C or -40 °C). Melt polycondensation was also used to prepare a series of all-aliphatic block and random copolyesters including the following aliphatic monomers: trans-DMCD, DMCD-2, neopentyl glycol (NPG), diethylene glycol (DEG) and dimethyl succinate (DMS). The polymer compositions were determined by 1H NMR, and the molecular weights were determined using SEC. The polyesters were also characterized by TGA, DSC, DMA and tensile tests. Phase separation was not observed in these block copolyesters. However, the block copolyester containing DMCD-2 and NPG was observed to have a higher Tg than the block copolyester based on trans-DMCD and NPG. In addition, these block copolyesters were found to have better mechanical properties than the corresponding random copolyesters. / Ph. D.

Dans un contexte du développement durable, de nouvelles architectures macromoléculaires biosourcées ont été synthétisées à partir de synthons (diacides et diols) pouvant être obtenus par voies fermentaires à partir de sources carbonées issues de la biomasse. Dans un premier temps, différents copolyesters aliphatiques ont été synthétisés en masse, à l’aide d’un catalyseur organométallique à base de titane, à partir de diacides (acides succinique et adipique) et de diols (1,3-propanediol, 1,4-butanediol et 2,3-butanediol) courts. Dans un deuxième temps, des architectures macromoléculaires similaires ont été obtenues par catalyse enzymatique en solution à l’aide de la lipase B de Candida antarctica. L’influence de la longueur et de la structure des monomères sur leur réactivité en présence de la lipase a été particulièrement étudiée. Dans un troisième et dernier temps, des architectures macromoléculaires à base d’oligomères hydroxytéléchéliques d’un polyester bactérien : le poly((R)-3-hydroxybutyrate) (PHB)tels que des poly(ester-éther-uréthane)s et des copolyesters ont été obtenues soit par couplage de chaîne à l’aide d’un diisocyanate, ou par transestérification organométallique et enzymatique. Ces études ont permis d’analyser en détail l’effet de l’addition des synthons biosourcés dans les architectures macromoléculaires et notamment sur la structure cristalline, la stabilité thermique et les propriétés thermiques et optiques de ces polymères. De plus, le grand potentiel de la catalyse enzymatique pour la synthèse de polyesters et celui de l’utilisation d’oligomères de PHB pour l’élaboration de nouveaux matériaux performants ont pu être largement démontrés. / In the context of sustainable development, new biobased and aliphatic macromolecular architectures were synthesized from building blocks that can be obtained by fermentation routes using carbon sources from the biomass. First, several aliphatic copolyesters were synthesized in bulk from short dicarboxylic acids (such as succinic and adipic acids) and diols (such as 1,3-propanediol, 1,4-butanediol and 2,3-butanediol) by organometallic catalysis using an effective titanium-based catalyst. In a second time, similar macromolecular architectures were synthesized by an enzymatic process in solution using Candida antarctica lipase B as catalyst. The influence of the alkyl chain length and the structure of monomers on their reactivity toward the lipase were particularly discussed. In the third and last part, new macromolecular architectures based on hydroxytelechelic oligomers of a bacterial polyester: poly((R)-3-hydroxybutyrate) (PHB), such as poly(ester-ether-urethane)s and copolyesters, were obtained by either chain-coupling using a diisocyanate, or organometallic and enzymatic transesterification, respectively.These studies permitted to determine a close relationship between the effect of the building blocks structure integrated in the final macromolecular architectures and the intrinsic properties, such as the crystalline structure, the thermal stability and the thermal and optical properties, of these polymers. In addition, the great potential of the lipase-catalyzed synthesis of polyesters and the use of PHB oligomers for developing new high performance materials has been clearly established.