Crystallization behavior and morphology of PE-g-LCP copolymers

 This study presents DSC and optical microscopy investigations on copolymers of semiflexible liquid crystalline polymer SBH 112 grafted to functionalized low molecular mass polyethylene (PEox) obtained by melt polycondensation or reactive blending procedures. The crystallization behavior of the PE-g-SBH copolymers has been studied under non-isothermal measurement conditions carried out at different cooling rates. The crystallization temperature (T _cr) of the PE component of the copolymers decreases steadily upon increasing the concentration of the SBH grafts. It was found that the copolymers prepared by reactive blending crystallize at slightly higher T _cr than those prepared by polycondensation and with a higher rate, confirmed by the determination of the crystallization rate coefficients (CRC). The results have been interpreted by the fact that the PE crystallizable segments and SBH grafts of the copolymers obtained by reactive blending are longer than those of the copolymers prepared by polycondensation. The overall nonisothermal crystallization kinetics has been studied by the Harnisch and Muschik equation. The results show that the mechanism of the crystallization of the PE phase changes only when the SBH content overruns ca.50%, due to the decrease of both nucleation and crystal growth rates. The morphology of the copolymers crystallized nonisothermally from melt has been examined by polarization microscopy. Fairly homogeneous morphology with tiny PE spherulites is observed for PE-g-SBH copolymers prepared by polycondensation with SBH as the minor phase. No sign of the dispersed LCP domains can be recognized. On the contrary, the morphology of the copolymers prepared by reactive blending is distinctly biphasic. The allegedly longer PE segments crystallize into tiny spherulites too, but the LC domains formed by the long SBH branches present in this type of copolymers appear clearly in the micrographs at room temperature. It is concluded that the copolymers prepared by reactive blending would be more effective as compatibilizers for PE/SBH blends than those prepared by polycondensation. Received: 9 October 1996 Accepted: 13 January 1997     

Morphology of siloxane block copolymers: Tetramethyl-p-silphenylene siloxane–dimethylsiloxane

The morphological features of random block copolymers of tetramethyl-p-silphenylene (TMPS) and dimethylsiloxane (DMS) have been studied as a function of copolymer composition. Wide-angle and small-angle x-ray diffraction coupled with several electron diffraction and microscopy studies were used to investigate these materials. The results of this work clearly indicate that the amorphous segments do not enter into the crystalline lattice of the crystallizable component which is varied in content from 90% to 30%. Over the entire range of compositions the block copolymers are crystallizable. Spherulites can be grown from the melt, and single crystals and/or spherulites may be obtained from solution. Single crystals can be obtained over the entire range of compositions provided ample time is allowed for crystallization. The crystalline TMPS component exhibits tetragonal symmetry at all compositions. The amorphous phase manifests itself as a diffuse halo in patterns obtained by electron and x-ray diffraction.     

Mechanical,aging, optical and rheological properties of toughening polylactide by melt blending with poly(ethylene glycol) based copolymers

Two novel biodegradable copolymers, including poly(ethylene glycol)-succinate copolymer (PES) and poly(ethylene glycol)-succinate-l-lactide copolymer (PESL), have been successfully synthesized via melt polycondensation using SnCl₂ as a catalyst. The copolymers were used to toughen PLA by melt blending. The DSC and SEM results indicated that the two copolymers were compatible well with PLA, and the compatibility of PESL was superior to that of PES. The results of tensile testing showed that the extensibility of PLA was largely improved by blending with PES or PESL. At same blending ratios, the elongation at break of PLA/PESL blends was far higher than that of PLA/PES ones. The elongation maintained stable through aging for 3 months. The moisture absorption of the blends enhanced due to the strong moisture absorption of PEG segments in PES or PESL molecules, which did not directly lead to enhance the hydrolytic degradation rate of the PLA. The PLA blends containing 20–30 wt% PES or PESL were high transparent materials with high light scattering. The toughening PLA materials could potentially be used as a soft biodegradable packaging material or a special optical material.     

共聚聚醚酯酰胺的多重转变及其相态结构

Segmented polyesteramides have been synthesized from N,N'-bis（p-carbomethoxybenzoy）butanediamine（T4T）as crystalline segments and mixture of poly（tetramethylene oxide）with the average molecular weight 1000（PTMO1000）and 1,5-pentanediol（PDO）as soft segments. The polymerization was carried out in the melt at 250℃ for 1-2 h while vacuum was applied. The chemical composition of the copolymer was measured by H1-NMR. The melting behavior of the copolymers was studied by the differential scanning calorimeter. The dynamic mechanical properties were investigated on injection moulded bars by means of dynamic mechanical analysis. It was found that the copolymers with more than 40% molar ratio PDO showed two glass transition temperatures and two melting temperatures. The glass transition temperatures are independent of composition,and thus two fully phaseseparated amorphous phases are present. The melting temperatures change with PDO content. The amount of PDO has an effect on both TmA and TmB . TmA is attributed to the lamella consisting of extended T4T segments,while TmB results from the much thicker lamella consisting of both extended T4T and PDO segments. It is also possible that some PDO is present in the interphase as adjacent re-entry groups. So the resultant copolymer shows that a complex system,two crystalline phases,two amorphous phases and an interphase are involved in the copolymer. The undercooling for these copolymers is small,which means that these segmented copolymers crystallize fast.     

Structure and property relationships in ethylene–vinyl acetate copolymers

The effects of vinyl acetate content on crystallinity of ethylene–vinyl acetate (E/VA) copolymers were investigated by x-ray diffraction and differential thermal analysis (DTA). The values of these parameters obtained from DTA were found to agree quantitatively with data calculated from x-ray, probability equations, and copolymer theory. The melting points of the crystalline copolymers, and the molar amounts of vinyl acetate to produce a completely amorphous rubber corresponds exactly to that predicted by the Flory theory. The random character expected in E/VA copolymers is thereby confirmed. The physical properties of E/VA copolymers of all ranges of compositions and crystallinity were determined. Depending directly upon vinyl acetate content, the copolymers changed progressively from highly crystalline polyethylene to semicrystalline polyethylene, a completely amorphous rubber, a soft plastic with a glass transition near room temperature. Properties which were correlated with copolymer composition include: crystallinity, melting point, density, modulus, tensile strength, glass transition, and solubility. Finally, the effect on crystallinity and physical properties of replacing the acetoxy group in E/VA with the smaller, highly polar hydroxyl group (ethylene—vinyl alcohol copolymer) was also investigated.     

甲基取代的新型聚醚醚酮及其共聚物的合成、表征和性能研究

设计合成了一种甲基侧基取代的可溶性聚芳醚酮均聚物PETMDEK,同时合成了一系列不同比例的无规共聚物PETMDEK-PEDEK,考察了共聚组成对聚合物性能的影响.随着共聚物中可溶性PETMDEK组分的不断增加,其聚集态结构也发生变化,出现从结晶→液晶→结晶→无定形固体的转变,同时溶解性也由可溶向不溶转变.本文还侧重研究了PETMDEK组分摩尔分数为20%的无规共聚物的热致液晶行为.     

聚(苯乙烯-ε-己内酯)嵌段共聚物的研究

本文采用活性阴离子聚合方法合成聚(苯乙烯-ε-己内酯)嵌段共聚物。研究了聚合反应条件,并用GPC、柱上溶解分级及红外光谱进行表征。对产物进行结构分析,产物为聚(苯乙烯-ε-己内酯)嵌段共聚物,具有多相结构,是由无定形聚苯乙烯链段、无定形聚-ε-己内酯链段和结晶型聚-ε-己内酯链段组成的嵌段共聚物。对该嵌段共聚物的性能进行了测试。     

Melting behavior of a poly(ether‐block‐amide) copolymer melt‐crystallized under quiescent,isothermal conditions

Segmented poly(ether‐block‐amide) copolymers are typically known as polyamide‐based thermoplastic elastomers consisting of hard, crystallizable polyamide block and flexible, amorphous polyether block. The melting characteristics of a poly(ether‐block‐amide) copolymer melt‐crystallized under various quiescent, isothermal conditions were calorimetrically investigated using differential scanning calorimetry (DSC). For such crystallized copolymer samples, their crystalline structures under ambient condition and the structural evolutions upon heating from ambient to complete melting were characterized using ambient and variable‐temperature wide‐angle X‐ray diffractometry (WAXD), respectively. It was observed that dependent of specific crystallization conditions, the copolymer samples exhibited one, two, or three melting endotherms. The ambient WAXD results indicated that all melt‐crystallized copolymer samples only exhibited γ‐form crystals associated with the hexagonal habits of the polyamide homopolymer, whereas variable‐temperature WAXD data suggested that upon heating from ambient, a melt‐crystallized copolymer might exhibit so‐called Brill transition before complete melting. Based on various DSC and variable‐temperature WAXD experimental results obtained in this study, the applicability of different melting mechanisms that might be responsible for multiple melting characteristics of various crystallized PEBA copolymer samples were discussed. It was postulated that the low (T _m1) endotherm was primarily because of the disruption of less thermally stable, short‐range ordered structure of amorphous polyamide segments of the copolymer, which was only formed after the completion of primary crystallization via so‐called annealing effects. The intermediate (T_m2) and high (T_m3) endotherms were attributed to the melting of primary crystals within polyamide crystalline microdomains of the copolymer. The appearance of these two melting endotherms might be somehow complicated by thermally induced Brill transition. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2035–2046, 2008     

Modifying an amorphous polymer to a fast crystallizing semi‐crystalline material by copolymerization with monodisperse amide segments

Segmented block copolymers of polysulphone with monodisperse amide segments were synthesized by a melt and a solution polymerization method. Both triblock and multiblock copolymers were prepared. The length of the difunctional polysulphone was varied from 2000 to 20,000 g/mol. The monodisperse amide segment was the tetra‐amide T6T6T based on terephthalic acid (T) and hexamethylene diamine (6) units. The main goal of this work was to study if the high T_g amorphous polysulphone could be modified to a high T_g semi‐crystalline PSU‐T6T6T copolymer. The copolymers were characterized by viscosity measurements, NMR, FTIR, MALDI‐TOF, DSC, and DMA. Depending on the amide concentration in the copolymers the T6T6T melting temperatures ranged between 220 and 270 °C and thus the crystallization window was small 50–100 °C. From the FTIR results, it was revealed that the crystallinity of the T6T6T segments in the copolymer could be very high, up to 92–97%. The T6T6T has crystallized out into nanoribbons with a high aspect ratio. These high T_g semi‐crystalline copolymers had a high dimensional and solvent resistance. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 63–73, 2010     

Synthesis and thermal characterization of poly(1,3-phenyl octanoate)

Poly(1,3-phenyl octanoate) (polyHPOA) was prepared by melt and solution polycondensation methods from 8-(3-hydroxyphenyl)octanoic acid (HPOA), a novel monomer useful as a chain disruptor in liquid crystalline copolyesters. The melt polycondensation technique gave a polyester of higher inherent viscosity (0.80 dL/g in p-chlorophenol) than that (0.75 and 0.56 dL/g, respectively, for the Ogata method and thionyl chloride/pyridine method in the same solvent) of solution techniques. The solubility of the polyesters was limited to strongly acidic and polar solvents. The polyester was characterized by elemental analysis, IR spectroscopy, WAXD, TGA, isothermal TGA and DTA. x-ray diffraction pattern of the polyesters indicated that it is amorphous in nature. TGA of the polyesters gave a thermal stability of 470°C in nitrogen atmosphere at 50% decomposition. The available thermal data suggest that the polyester undergoes thermal decomposition by a pyrolytic cleavage involving the ester linkage with the formation of ketene and phenol ended groups as intermediates. © 1996 John Wiley & Sons, Inc.     

蓖麻油与乳酸的共聚物合成与表征

用熔融聚合法合成了一种蓖麻油和乳酸的共聚物.以丁二酸酐作为共聚体系的引发剂和封端剂,制得端羧基共聚物P(LA-CO)-COOH.研究了反应条件对共聚物分子量的影响,通过核磁共振表征了共聚物的结构.DSC和TG研究表明,蓖麻油链段的引入破坏了聚乳酸的结晶性,提高了共聚物的热稳定性.     

Structure and properties of new polyester elastomers composed of poly(trimethylene terephthalate) and poly(ethylene oxide)

Series of PTT-b-PEO copolymers with different composition of rigid PTT and PEO flexible segments were synthesized from dimethyl terephthalate (DMT), 1,3-propanediol (PDO), poly(ethylene glycol) (PEG, M_n = 1000 g/mol) in a two stage process involving transesterification and polycondensation in the melt. The weight fraction of flexible segments was varied between 20 and 70 wt%. The molecular structure of synthesized copolymers was confirmed by ¹H NMR and ¹³C NMR spectroscopy. The superstructure of these polymers was characterized by DSC, DMTA, WAXS and SAXS measurements. It was observed that domains of three types can exist in PTT-b-PEOT copolymers: semi-crystalline PTT, amorphous PEO rich phase (amorphous PEO/PTT blended phase) and semi-crystalline PEO phase. Semi-crystalline PEO phase was observed only at temperature below 0 °C for sample containing the highest concentration of PEO segment. The phase structure, thermal and mechanical properties are effected by copolymer composition. The copolymers containing 30÷70 wt% of PEO segment posses good thermoplastic elastomers properties with high thermal stability. Hardness and tensile strength rise with increase of PTT content in copolymers.     

Synthesis and Enzymatic Degradation of Aliphatic Polyesters Copolymerized with Trimesic Acid

Abstract

Network copolyesters were made from adipic acid and ethylene glycol with 10–40 mol% trimesic acid (Y). Prepolymers prepared by melt polycondensation were cast from dimethylformamide solution and postpolymerized at 260°C for various times to form a network. The degree of reaction (D _R), estimated from the infrared absorbance of hydroxyl and methylene groups, increased with increasing postpolymerization time and leveled out at about 90% after 4–6 hours. Heat distortion temperatures (T _h) measured by thermomechanical analysis increased greatly from ?83 to 48°C upon the incorporation of Y. Wide-angle x-ray diffraction patterns showed that the copolymer films are amorphous. Density, tensile strength, and Young's modulus decreased for the copolymers with 10–30 mol% Y, whereas they increased drastically for the copolymer with 40 mol% Y. The enzymatic degradation was estimated by the weight loss of the copolymer films in buffer solutions with a lipase at 37°C. The weight loss decreased remarkably with increasing Y and showed no weight loss for the copolymer with 40 mol% Y. On the other hand, the weight loss by alkali hydrolysis increased for the copolymers with 10 and 20 mol% Y, implying a difference in the degradation mechanism between enzymatic degradation and alkali hydrolysis.     

Crystallization of branched polymers. I. Ethylene–vinyl acetate and ethylene–acrylic acid copolymers

The following quantities were measured on a number of ethylene–vinyl acetate (EVA) and ethylene–acrylic acid (EAA) copolymers: (1) the small-angle x-ray scattering invariant, (2) the overall density, and (3) the crystallinity. Assuming a two-phase structure, the separate values of the densities of the crystalline and amorphous regions can be calculated from these data. Of these, the crystalline density is compared with the value obtained from the lattice constants. A systematic difference is observed which is ascribed to the presence of comonomeric side groups in the crystalline regions. For the EVA and EAA samples, their concentration is at least 0.3 and 0.5 times the overall concentration, respectively. The amorphous densities are found to be higher than the values calculated from completely amorphous copolymers by extrapolation procedures.     

Polymer-metal halide interactions

Zirconium tatrafluoride forms stable complexes with Nylon 6 and caprolactam entailing the amide moieties. In compositions up to 5% ZiF₄ the crystalline structure of the polyamide appears unaffected by the complexed chain segments formed during melt blending. These segments become upon solidification part of the amorphous regions of the polyamide. This molecular reinforcement results in significant increases in both yield stress and tensile modulus. The polyamide compositions are characterized by increased rates of nucleation and a stable, fine crystalline structure in the solid state.     

Synthesis and morphology of all‐conjugated donor–acceptor block copolymers based on poly(3‐hexylthiophene) and poly(naphthalene diimide)

A series of all‐conjugated diblock and triblock copolymers comprised of poly(naphthalene diimide) (PNDI)‐based n‐type and the poly(3‐hexylthiophene) (P3HT) segments could be synthesized via the Kumada catalyst‐transfer polycondensation process. The crystalline structures and chain orientation of the block copolymer thin films were systematically studied by grazing incident wide‐angle X‐ray scattering (GIWAXS). The GIWAXS results indicated that both the P3HT and PNDI segments in the block copolymers form exclusive crystalline domains in which the P3HT domain aligns with an edge‐on rich orientation, and the PNDI domain aligns with a face‐on rich orientation. In contrast, the blend films of the P3HT and PNDI homopolymers also show two distinguished crystalline domains in which the P3HT domain aligns with an edge‐on rich orientation, and the PNDI domains align in different ways depending on the chemical structure of n‐type polymers, that is, PNDI1Th is isotropically dispersed, while PNDI2Th aligns with a face‐on rich orientation. In addition, the effect of thermal annealing on the crystalline behavior of the block copolymers is reported. The GIWAXS results indicated that thermal annealing increases the crystallinity of both segments without affecting their chain orientation. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1139–1148     

降冰片烯封端的聚苯乙烯大分子单体与乙烯共聚的初步报告

大分子单体(macromer)共聚合为合成结构确定的接枝共聚物提供了新途径,但用络合催化剂进行共聚的例子很少。前文报导了末端为降冰片烯(NB)的聚苯乙烯大分子单体PS-NB的合成及表征;现报告其与乙烯的共聚,以制备主干为聚乙烯(PE)、支链为聚苯乙烯(PS)的接枝共聚物PE-g-PS的初步结果。     

Synthesis,characterization, and properties of amphiphilic chitosan copolymers with mixed side chains by click chemistry

Novel amphiphilic chitosan copolymers with mixed side chains of poly(ε‐caprolactone) and poly(ethylene oxide) (CS‐g‐PCL/PEO) were successfully synthesized by “graft to” approach via click chemistry. The melting and crystallization behaviors and crystalline morphology of CS‐g‐PCL/PEO copolymers can be adjusted by the alteration of the feed ratio of PCL and PEO segments. CS‐g‐PCL/PEO copolymers revealed crystalline morphology different from that of linear alkynyl PCL and alkynyl PEO due to the influence of brush structure of copolymers and the mutual influence of PCL and PEO segments. The hydrophilicity of the CS copolymers can be improved and adjusted by the alteration of the composition of PCL and PEO segments. Moreover, the CS copolymers can self‐assemble into spherical micelles in aqueous solution. Investigation shows that the size of the CS copolymer micelles increased with the increase of the content of hydrophobic PCL segments in copolymers, which indicated that the micellar behavior of the copolymers can be controlled by the adjustment of the ratio of PCL and PEO segments in copolymer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3476–3486, 2010     

Thermotropic semi-rigid copoly(imide-carbonate)s composed of 3,4,3,4-p-terphenyltetracarboxdi-imide and 3,4,3',4'-biphenyltetracarboxdi-imide rings

New semi-rigid copoly(imide-carbonate)s composed of 3,4,3",4"-p-terphenyltetracarboxdi-imide and 3,4,3',4'-biphenyltetracarboxdi-imide units and neighbouring homologous penta- and hexa-methylene spacer chains were prepared by melt polycondensation; the relationships between polymer structure and liquid crystalline (LC) properties are discussed. Differential scanning calorimetry measurements, polarizing microscope observations, miscibility tests and variable temperature X-ray analyses suggest that the 3,4,3",4"-p-terphenyltetracarboxdi-imide-rich copolymers form thermotropic LC nematic and smectic phases, but the 3,4,3',4'-biphenyltetracarboxdi-imide-rich copolymers are amorphous and have no LC melts. Therefore, the presence of 3,4,3",4"-p-terphenyltetracarboxdi-imide units confers good mesogenic properties.