Sequence distribution and thermal properties of poly(butylene naphthalate terephthalate)

Poly(butylene naphthalate terephthalate) (PBNT) copolyesters were synthesized from bis(4-hydroxybutyl) terephthalate (BHBT) and bis(4-hydroxybutyl) naphthalate (BHBN) as starting materials. BHBT and BHBN were either homopolymerized or copolymerized at 260∼270 °C in the presence of titanium tetrabutoxide (TBT) as a catalyst to provide PBNT with various compositions. The copolyesters were characterized using inherent viscosity, X-ray, d.s.c., t.g.a. and ¹H NMR. The composition and sequence distribution of the copolyesters was determined from ¹H NMR spectra. The copolyesters exhibited a degree of randomness of about 1, indicating that the reactivity of BHBT and BHBN was almost the same. X-ray and d.s.c. showed PBNT copolyesters to be crystalline polymers. T.g.a. kinetics showed PBNT copolyesters to exhibit higher degradation activation energy, that is, better thermal stability, than PBTs.     

Poly(ethylene terephthalate) copolyesters and fibers modified with NPG and SIPE for improved hydrophilicity and dyeability

A series of Poly(ethylene terephthalate) (PET)-based copolyesters containing sodium-5-sulfo-bis-(hydroxyethyl)-isophthalate (SIPE) and 22-dimethyl-13-propanediol (NPG) were successfully synthesized. The results showed that the actual molar ratio of comonomers was consistent with the relative feed ratio, and the thermal properties of copolyester were greatly dependent on the amount of NPG. Meanwhile, the modified PET fibers were prepared via traditional melting-spinning and the effects of NPG amounts and draw ratio on the crystallinity, orientation, and mechanical property of the fibers were also investigated. Furthermore, the hydrophilic property and dyeability of the fibers were explored. The results showed that compared with the pure PET fibers, the resultant fibers exhibited improved hydrophilicity and dyeability, which also were controllable by tuning the amount of NPG and in turn provided the modified PET fibers with more potential application in various fields.     

Microstructure analysis and thermal properties of l-lactide/?-caprolactone copolymers obtained with magnesium octoate

A series of copolymers with various compositions were prepared by the ring opening copolymerization of l-lactide (l-LA) and ?-caprolactone (?-CL) using nontoxic magnesium octoate as a catalyst in bulk. The copolymerization process and the influence of transesterification on the chain microstructure were examined by ¹H and ¹³C NMR. A tapered block or gradient copolymer is expected to be formed on the basis of the reactivity difference between l-LA and ?-CL. Two modes of transesterification occurred and played an important role in the redistribution of comonomer sequences but not a completely random distribution. The CLC sequence formed by the second mode of transesterification was observed at the end of reaction. The coefficient of the second mode of transesterification (T_II) increased as the feed mole fraction of ?-CL increased. In terms of the overall feed compositions, the L_LL^r values of lactidyl sequences calculated from the reactivity ratio exceeded the L_LL^e values determined from the product, however, the L_C^r values of caproyl sequences were identical or shorter than the L_C^e values. The thermal properties and crystallinities of the obtained copolymers were investigated by DSC and WAXD. The thermal properties and crystallinities depend on both the composition and the chain microstructure. The l-LA/?-CL copolymer with intermediate composition exhibited some blocky character by DSC. Only single T_g was observed for each copolymer and in agreement with the calculated value from Fox equation, indicating that the amorphous region of the copolymers is miscible. The obtained copolymers can best be described as random copolymers with more or less blocky chain structure.     

聚(对苯二甲酸丁二醇酯-co-衣康酸丁二醇酯)的合成及表征

以对苯二甲酸二甲酯(DMT)、1,4-丁二醇和生物质来源的衣康酸二甲酯(DI)为原料,采用熔融缩聚法制备了一类生物可降解脂肪族/芳香族共聚酯—聚(对苯二甲酸丁二醇酯-co-衣康酸丁二醇酯)(PBTI),并考察了缩聚反应时间、缩聚温度和DMT与DI的物质的量比对PBTI相对分子质量和热力学性质的影响。利用1 H-NMR和FT-IR对PBTI的结构进行了确认,同时GPC、DSC和TGA测试结果表明,相对分子质量、玻璃化转变温度和熔点都受共聚酯中DMT与DI比例的影响。另外还探究了DMT与DI的物质的量比对该类共聚酯降解性的影响,结果表明,随脂肪族链段的增加共聚酯的降解性逐渐增加。     

全芳族热致液晶共聚酯的性能研究

通过酯交换反应,合成了一系列以对乙酰氧基苯甲酸(PHB),4.4,—二乙酰氧基二苯基丙烷(BPA)和对苯二甲酸(TPA)为单体的三元共聚酯。采用热台偏光显微镜(TOT)、示差扫描量热仪(DSC)和广角x射线衍射(WAXD),较详细地研究了液晶共聚酯的结构、性能及其与分子链组成的关系。DSC和TOT结果表明,共聚酯的玻璃化温度较高,介于166—188℃之间,熔化温度一组成关系的相图具有最低共熔点;共聚酯中PHB链节含量在10～50％时均呈现向列型液晶特征,随温度升高.均无各向同性转变,固态共聚酯具有冻结向列液晶结构。WAXD结果指出无规共聚是破坏结晶结构,降低熔点的有效手段。     

Tailoring block‐copolyesters by reactive blending of polyethylene terephthalate and polyethylene naphthalate using statistical design of experiments

Block‐copolyesters of polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) were synthesized via reactive extrusion. The influence of processing parameters on the material properties on a molecular scale like degree of trans‐esterification, block length, and degree of randomness were investigated. The varied process factors were extrusion temperature and rotational speed. The effects of process parameter variation were investigated by ¹H‐NMR‐spectroscopy. The experimental results show a clear dependence of the molecular properties on the processing conditions. By using statistical experimental design (DoE), it was possible to prepare defined copolyesters from PET and PEN without addition of further chemicals. With a degree of randomness between 0.05 and 0.5, the presence of an actual copolyester was confirmed when appropriate extrusion conditions were applied. The reactive extrusion process was confirmed to be suitable to produce defined block‐copolyesters in a predictable and reproducible way. It was possible to produce designed sequence lengths, which could be adjusted within a range of 11–136 repeating units in the case of PET and, in the case of PEN, of 2.5–26. The produced materials can be used as barrier materials or barrier coatings to protect substrates against molecular oxygen and water vapour, e.g., in organic photovoltaic applications or food packaging. The described method is a one‐pot alternative method to the previously described chemical recycling pathway. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41997.     

Aromatic-aliphatic copolyesters: structure and properties

Aromatic-aliphatic copolyesters synthesized by interfacial polycondensation were characterized by differential scanning calorimetry. X-ray diffraction and density measurements. A decrease in the T_g and melting temperature was observed on increasing the glycol content of the copolyesters. The wholly aromatic polyesters showed changes both in the Bragg angle position and intensity of the reflections, whereas in the aromatic-aliphatic copolyesters no sharp change was observed.