Proton NMR characterization of chain structure in butylene terephthalate-ϵ-caprolactone copolyesters

A series of butylene terephthalate-ϵ-caprolactone copolyesters (BCL) with different hard-segment content were synthesized and their chain structures were carefully investigated by high resolution ¹H-NMR spectroscopy. The analysis from ¹H-NMR spectra of samples reveals that BCL chain chemical and sequence structure is specific and complicated because of the unavoidable transesterification between BT and CL segments during synthesis process and so BCL copolyesters are segmented copolyesters with certain random property as confirmed by DSC measurements. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3770–3777, 1999     

Shape Memory Properties in Poly(ethylene oxide)–Poly(ethylene terephthalate) Copolymers

Memory effects of several copolymers of poly(ethylene oxide) (PEO) and poly(ethylene terephthalate) (PET) were illustrated with photos, determined with shrinkage experiments and characterized by the recovery of samples to their original figures. Copolymers of appropriate composition could undertake an approximately full recovery which is tightly related to the annealing temperature at which shrinkage of samples occurs to some extent. Melting and recrystallization of PEO segments may be responsible for the memory effect. The memory properties of samples almost kept unchanged after many fatigue cycles (e.g. 15–20 cycles), which could make these copolymers useful in practical applications as novel shape memory materials. © 1997 John Wiley & Sons, Ltd.     

Effect of Orientation on the Biodegradability of Aliphatic Copolyester Blown Films

The effects of process conditions on the orientation of aliphatic copolyester-blown films were investigated by using both Fourier transform infrared–attenuated total reflection (FTIR–ATR) dichroism and wide-angle X-ray diffraction (WAXD) methods. The results showed that a large increase in orientation was obtained by increasing the drawdown ratio (DDR). However, an unbalanced orientation was clearly shown at high DDR. A high blowup ratio was accompanied by reduced chain relaxation as well as fast crystallization, leading to more balanced films. The WAXD patterns of blown films exhibited the preferential orientation of lamellar crystallites. The results of microbial degradation indicated that the development of planar orientation evidently depressed biodegradability of samples. Video microscopy observations revealed that the degree of orientation played a dominant role in determining the rate of surface erosion. © 1997 John Wiley & Sons, Ltd.     

嵌段共聚酯的合成研究

采用直接酯化法合成了一系列含间苯二甲酸的PEIT－PEG嵌段共聚酯,研究了聚合时间,聚合效率及聚酯的特性粘度与产物中间苯二甲酸含量及共聚酯分子量的关系,得出适于纺丝工艺及工业化生产的共聚酯分子量和间苯二甲酸的含量。     

Investigations of transesterification in PC/PBT melt blends and the proof of immiscibility of PC and PBT at completely suppressed transesterification

The miscibility of polycarbonate PC and poly(butylene terephthalate) PBT is controversially discussed in the literature. Partial miscibility has been generally found in melt blends of the two polymers. However, in solution cast blends they were found to be immiscible. It is known that the transesterification takes place in the melt. Copolyesters formed by the transesterification change the compatibility of PC and PBT. In this work PC/PBT melt blends of various composition were investigated in dependence on the copolyester content by means of DSC and NMR. It can be shown that the time regime of the thermal treatment in the melt determines the transesterification degree. The PBT crystallization behavior is strongly influenced by both the PC and copolyester content. The glass transition temperatures of the PBT-rich and PC-rich phase approach each other with the increasing copolyester content. The analysis of the glass transition behavior permits the conclusion that PC and PBT are inherently immiscible provided that the copolyester content is exactly zero. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2161–2168, 1997     

Glass transition broadening via nanofiller-contiguous polymer network in aromatic thermosetting copolyester nanocomposites

The glass transition is a genuine imprint of temperature-dependent structural relaxation dynamics of backbone chains in amorphous polymers, which can also reflect features of chemical transformations induced in macromolecular architectures. Optimization of thermophysical properties of polymer nanocomposites beyond the state of the art is contingent on strong interfacial bonding between nanofiller particles and host polymer matrix chains that accordingly modifies glass transition characteristics. Contemporary polymer nanocomposite configurations have demonstrated only marginal glass transition temperature shifts utilizing conventional polymer matrix and functionalized nanofiller combinations. We present nanofiller-contiguous polymer network with aromatic thermosetting copolyester nanocomposites in which carbon nanofillers covalently conjugate with cure advancing crosslinked backbone chains through functional end-groups of constituent precursor oligomers upon an in situ polymerization reaction. Via thoroughly transformed backbone chain configuration, the polymer nanocomposites demonstrate unprecedented glass transition peak broadening by about 100 °C along with significant temperature upshift of around 80 °C. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1595–1603     

Attempt to control monomer sequences in copolycondensations of IPA,TPA, BPA,and PHB

Copolycondensations of IPA, TPA, BPA, and PHB were studied to investigate how PHB, which can form mesogenic segments, should be incorporated into the amorphous IPA/TPA–BPA polyester to obtain the thermotropic copolyester, unlike other copolymerizations studied so far by randomly introducing nonmesogenic components into the liquid crystalline polyesters. Random and controlled copolycondensations were attempted to regulate the segment length of mesogenic PHB units by stepwise addition of BPA and PHB through the two- and three-stage reactions using TsCl/DMF/Py as a condensing agent. Thermotropic copolyesters with ca. 40 mol % PHB could be obtained by a three-stage reaction, despite that more than 70 mol % PHB is needed to prepare by usual random copolymerization with PHB. The segment length of the PHB unit was indirectly studied from IPA/TPA–BPA oligomer distribution at initial reaction by means of GPC and from the NMR analysis of the resulting copolymers. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2371–2377, 1999     

Ester–amide exchange in blends of liquid‐crystalline copolyester and polyamide 6

The kinetics of the ester–amide exchange in solution blends of the random liquid‐crystalline polyester copoly(oxybenzoate‐terephthalate) (P64) and polyamide 6 (PA6) were studied with carbon nuclear magnetic resonance. With second‐order reversible reactions assumed, the activation energy of the ester–amide interchange in 30/70, 50/50, and 70/30 P64/PA6 blends were all about 24.0 kcal/mol. The pre‐exponential factors for the ester–amide exchange in 30/70, 50/50, and 70/30 P64/PA6 blends were 2.01 × 10¹¹, 2.59 × 10¹⁰, and 2.74 × 10¹² min⁻¹, respectively. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2124–2135, 2000     

含异山梨醇的全生物基PBS嵌段共聚酯的制备及性能

采用熔融扩链法制备了高分子量的全生物基聚丁二酸丁二醇酯(PBS)-聚丁二酸异山梨醇酯嵌段共聚酯.GPC测试结果表明,该嵌段共聚酯在较高的异山梨醇(Is)含量时仍具有较高的分子量,其M_n介于3.5×10~4~7.0×10~4之间.采用TGA和DSC对嵌段共聚酯的热稳定性和结晶性能进行了研究,结果表明嵌段共聚酯保持了PBS优异的热稳定性和结晶性能,即使异山梨醇含量达60 mol%,其熔点较PBS仅下降2 K.采用DMA分析了嵌段共聚酯的玻璃化转变温度T_g,发现随着异山梨醇含量的增加,其T_g随之升高,当Is含量为60mol%时,嵌段共聚酯的T_g高达68℃,并且共聚酯的2个链段具有很好的相容性.力学性能测试结果表明,异山梨醇的引入可使PBS的力学性能得到明显地提高和调控,随着异山梨醇含量的增加,嵌段共聚酯的拉伸强度先增加后降低,断裂伸长率约是PBS的2倍,其中,当异山梨醇含量达60 mol%时,嵌段共聚酯的屈服强度由PBS的35.0 MPa增至43.0 MPa.     

Synthesis and characterization of potentially biodegradable thermotropic polyesters based on p-hydroxybenzoic acid and glycolic acid

The synthesis of novel thermotropic liquid crystalline copolyesters derived from aliphatic hydroxy acid (glycolic acid, GA) and aromatic hydroxy acid (p-hydroxybenzoic acid, PHBA) via a melt-copolycondensation process in the presence of various catalysts was explored. The following three possible routes were checked: PHBA and GA in different feed ratios with or without a catalyst; PHBA and GA in different feed ratios with or without a catalyst in the presence of acetic anhydride as a condensation agent; and different PHBA derivatives were used to examine the reactivity of aromatic hydroxy acid. The copolycondensability, chemical structure, liquid crystallinity, textures and morphology, phase transition behaviors and thermal stability, and solubility were investigated by FTIR, NMR, DSC, TGA, and polarized-light microscope. It has been found that only the 60–70 mol % PHBA-containing copolyesters could exhibit a nematic liquid crystallinity. The as-prepared polymers were brittle due to relatively lower molecular weights. © 1994 John Wiley & Sons, Inc.