This tutorial review summarizes recent developments in the syntheses of functionalized aliphatic polyesters. These polymers are attracting attention as sustainable alternatives to petrochemicals and for applications in medicine. Two main syntheses are described: step polymerization using mild chemo/enzymatic catalysis and ring opening polymerization, which is usually initiated by metal complexes. The methods are compared and their utility illustrated with reference to interesting new materials. 相似文献
Ester-exchange and polycondensation reactions of active diesters such as diphenyl, dithiophenyl, or dipyridinyl esters of adipic or terephthalic acids with glycols were carried out in order to investigate the reactivity of these active diesters toward nucleophilic replacement. Catalysts such as potassium carbonate were required for the esterexchange of these active diesters. Comparison of the reactivity of these active diesters with that of ordinary diesters in the presence of potassium carbonate as a catalyst indicates the rates or the equilibrium constants of the exchange reactions of these active diesters were much larger than those of ordinary diesters, indicating that polyesterification reactions favorably occur. Polyesters were obtained in good yield either by solution or bulk methods in mild conditions. 相似文献
Thermally reversible polyesters were obtained by the ester formation reaction of thermoplastic polyesters with hydroxyl end groups and the diacid anhydride of tetra carboxylic acid as a thermally reversible chain extender. Typical example of the thermally reversible polyesters was obtained by the reaction of PBT (polyburylene terephthalate) and PMA (pyromellitic dianhydride). This material having twice as large molecular weight as the original PBT exhibited almost the same melt viscosity as the original. Also that thermally reversible chain extension reaction occurred without unfavorable side reaction such as cross-linking. This material shows both good processability and superior mechanical properties due to its thermally reversible characters. 相似文献
Six new aromatic polyesters were synthesized by the phase-transfer catalytic polycondensation. The polymers obtained were characterized by infra-red, X-ray diffraction, D.S.C., depolarized light intensity and polarizing microscope. Poly(p,p'-hydroquinone-1,4-phenylene dioxyacetate) and poly(p,p'-hydroquinone-1,4,7-trioxaheptamethylene dibenzoate) were found to be thermotropic liquid crystals but related polyesters are not. The results are discussed on the basis of the thermodynamic data obtained. 相似文献
End-functionalization of biodegradable polymers/oligomers based on L-lactide and glycolide by cholesteryl moiety was investigated. We established the feasibility of preparing the functionalized polymers/oligomers, Chol-(LG)m+n, through ring-opening copolymerization initiated by cholesterol bearing a hydroxyl group, without adding any catalyst. The functionalized polymers/oligomers of different molecular weights were obtained by controlling the feed ratio of the initiator cholesterol to the monomers. The chemical structure of end-functionalized polymers/oligomers was confirmed by FTIR and 1H NMR. Incorporation of cholesteryl moiety into the polymer chains induces liquid crystallinity in the resultant oligomers when the molecular chains are not very long. The enzymatic degradation studies, for all the samples, were carried out using enzyme, proteinase K. Interestingly, the enzymatic degradation of cholesteryl end-functionalized polymers/oligomers resulted in a lamella-like porous structure on the sample surface, which is altogether different from the commonly reported spherical-pore structure formed during the degradation of conventional polyesters. 相似文献
A new group of photocrosslinkable polyesters formed by the Knoevenagel reaction is described. The approach permits preparation of photoesensitive polymers, where physical properties can be potentially varied through choice of the polyol and the dicarboxylic acid. The following compounds were prepared and studied: (1) products from a Knoevenagel reaction of poly(trimethylopropane azelate cyanoacetate) with benzaldehyde, furaldehyde, and 2-ethylbutyraldehyde and (2) products from a Knoevenagel reaction of poly(1,3-propyl malonate) with benzaldehyde, p-methoxybenzaldehyde, and 2-ethylbutyraldehyde. Conventional unsaturated polyesters such as poly(1,3-propyl fumarate) and poly(1,3-propyl maleate) were prepared and used for comparison. 相似文献
Abstract Six new aromatic polyesters were synthesized by the phase-transfer catalytic polycondensation. The polymers obtained were characterized by infra-red, X-ray diffraction, D.S.C., depolarized light intensity and polarizing microscope. Poly(p,p'-hydroquinone-1,4-phenylene dioxyacetate) and poly(p,p'-hydroquinone-1,4,7-trioxaheptamethylene dibenzoate) were found to be thermotropic liquid crystals but related polyesters are not. The results are discussed on the basis of the thermodynamic data obtained. 相似文献
Poly(ethylene naphthalates) containing small contents of N, N'-bis(ω-hydroxypropyl)naphthalene-1, 4, 5, 8-tetracarboxylic imide(HPNTI) unit as the photostabilizing component, which are stable to ultraviolet lights, were synthesized from dimethyl naphthalate, ethylene glycol, and HPNTI. The polyesters obtained were characterized by fluorescence spectroscopy and measurements of molecular weights and thermal properties. 相似文献
The synthesis of polythioethers of the form was effected, where Cp denotes cyclopentadienyl. Four reaction systems were studied and evaluated. Two proved to be undesirable (the “reverse” interfacial and organic solution methods), while two proved acceptable (the “normal” interfacial and aqueous solution methods). A number of added bases were evaluated. Et3N and NaOH were found to be acceptable. Yield increases with reaction time for aqueous solution syntheses, while yield remains constant with reaction time for synthesis via the normal interfacial method. 相似文献
Several polyesters containing thiaxanthone rings were prepared from 2,7-dichloroformylthiaxanthone-5,5′-dioxide ( IVa ), 2,8-dichloroformylthiaxanthone-5,5′-dioxide ( IVb ), and bisphenols by solution polycondensation. The 2,8-diethoxycarbonylthiaxanthone-5,5′-dioxide ( V ) was prepared and characterized by spectral methods to confirm the formation of 2,8-thiaxanthonedicarboxylic acid-5,5′-dioxide ( IVb ). Prior to polymer synthesis two model compounds,2,7-diphenoxycarbonylthiaxanthone-5,5′-dioxide (MDE-1) and 2,8-diphenoxycarbonylthiaxanthone-5,5′-dioxide (MDE-2), were synthesized and characterized by spectral methods. The polyesters were obtained in 62–78% yield and had inherent viscosities in the range 0.42–0.90 dL/g. The effect of thiaxanthone rings on solubility, crystallinity, and thermal stability of the polyesters are also discussed. The polyesters have decomposition temperatures in the range 372–438°C. 相似文献
Several series of liquid-crystalline side group polymers with a polyester backbone structure have been synthesized using mesogenic diethylmalonate and 1,3-propanediol derivatives. The structures of the polymer backbone and the mesogenic units have been varied systematically. As shown by differential scanning calorimetry, polarizing microscopy and X-ray diffraction, the side group polyesters exhibit nematic and/or smectic mesophases. Polyesters synthesized from mesogenic diethylmalonate derivatives can tolerate long non-mesogenic segments in the polymer main chain without losing their liquid crystal properties. X-ray studies suggest that some of the smectic polymers exhibit interdigitated bilayer SA phases. 相似文献
Summary By joint oxidative dehydropolycondensation of p-diethynylbenzene and dipropargyl esters, polymers have been obtained that contain triple bonds alternating with ester groups. 相似文献