Relationships between the molecular architecture,crystallization capacity,and miscibility in poly(butylene terephthalate)/polycarbonate blends: A comparison with poly(ethylene terephthalate)/polycarbonate blends

Poly(butylene terephthalate) (PBT)/polycarbonate (PC) samples, prepared via reactive blending in the presence of Ti‐ and Sm‐based catalysts, resulted in block copolymers whose block length decreased as the mixing time increased. A single homogeneous amorphous phase occurred when the blocks had monomeric sequences shorter than 10 units. Otherwise, a crystalline phase of PBT developed. Also, in poly(ethylene terephthalate) (PET)/PC blends previously studied, the miscibility was strictly correlated with the crystallizability of the system. Therefore, the miscibility of the PBT/PC and PET/PC blends was compared with respect to the tendency of the PBT and PET blocks to crystallize under isothermal conditions. The crystallization rate of the PBT/PC copolymers was faster than that of the PET/PC copolymers with similar block lengths. Accordingly, the minimum crystallizable sequence length of the PBT blocks was shorter than that of the PET blocks (18 vs 31 monomeric unit sequences). This behavior was interpreted as an effect of the more flexible PBT units, which had a greater tendency to fold and crystallize than the PET units. Therefore, PBT, the blocks of which tended to crystallize even if they were very short and phase‐separated, was characterized by a poorer compatibility with PC than that of PET. As a result, the block size had a fundamental role in determining the crystallizability and, therefore, phase behavior of the semicrystalline block copolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2821–2832, 2004     

PHASE STRUCTURE AND THERMAL BEHAVIOR OF LIQUID CRYSTALLINE MULTI-BLOCK COPOLYMERS,POLY[1,6-BIS(4-OXYBENZOYL-OXY)HEXANE TEREPHTHALATE]-b-BISPHENOL A POLYCARBONATE

Liquid crystalline multi-block copolymers poly [1,6-bis(4-oxybenzoyl-oxy)hexane terephthalate]-b-bisphenol A polycarbonate (PHTH-6-b-PC) with different segments of polycarbonate (PC) and thermotropicpolyester PHTH-6 were synthesized in tetrachloroethane at 144～146℃, The influence of segment length onthe resulting phase structure and thermal behavior of block copolymers was also discussed. It is demonstratedby TEM and DMA that the resulting block copolymers show a considerable microphase separation. Thedegree of phase separation and the thermal behavior of the block copolymers are strongly dependent on themolecular weight of the segments incorporated.     

两嵌段共聚物PB-PDMS中PDMS的结晶行为与共聚物形态结构的关系

聚二甲基硅氧烷(PDMS)的结晶熔融温度(T_m)约为-43℃,远高于其玻璃化转变温度(T_g)(-124℃),为扩大其低温使用范围,需要破坏其链结构规整性以抑制结晶发生。但是我们发现在前人工作中,含PDMS段的嵌段共聚物,即使不破坏PDMS段的链结构规整性,其动态力学谱上有时也观测不到PDMS的结晶峰。遗憾的是这些作者末曾对这一不寻常现象给予足够的重视。无疑,搞清共聚物中PDMS不寻常结晶行为同共聚物形态结构的关系,对提高含有PDMS段的嵌段型热塑性弹性体的低温使用范围将有指导意义。本文报导PB-PDMS中的结晶行为与共聚物形态结构的关系。     

含聚碳酸酯、4-羟基苯甲酸、己二醇和1,4-苯二甲酸结构的嵌段共聚物的合成与表征

以端酰氯基团的热致液晶共聚酯ＨＴＨ ６和端酚羟基的聚碳酸酯（ＰＣ）齐聚物为原料，通过溶液缩聚法制备了含ＰＣ和ＨＴＨ ６的嵌段共聚物，并用ＩＲ、ＰＯＭ、ＤＳＣ、ＷＡＸＤ等手段对共聚物结构、热行为和结晶行为进了表征．ＤＳＣ和ＰＯＭ结果证明这些嵌段共聚物都属向列型热致性液晶．在２８０℃以下的温度范围内无相分离，而在较高温度（＞２８０℃）为两相结构．共聚物的结晶结构与ＨＴＨ ６相同，结晶度随ＨＴＨ ６含量增加而增加，结晶速度也受到ＰＣ含量的影响．     

嵌段序列对聚合物囊泡形成过程影响的Monte Carlo模拟

采用Monte Carlo模拟方法研究了具有相同链长和组分比的不同嵌段序列的AB两嵌段共聚物与ABA三嵌段共聚物在选择性溶剂中形成囊泡的动力学过程. 模拟结果表明, AB两嵌段共聚物囊泡的形成与ABA三嵌段共聚物囊泡的形成的动力学过程不同. 在慢速退火条件下, ABA三嵌段共聚物囊泡是通过亲水链段向胶束的表面和中心扩散而形成的, 而AB两嵌段共聚物囊泡则由片层弯曲闭合而形成. 相对而言, 退火速度对AB两嵌段共聚物囊泡形成的动力学过程没有显著影响, 其改变仅影响亲水链段与疏水链段发生相分离的难易程度. 当退火速度较快时, 亲水链段和疏水链段发生相分离的速度较快且相分离发生在囊泡形成之前; 而当退火速度较慢时亲水链段和疏水链段之间的相分离在囊泡形成之后仍在进行.     

Isothermal crystallization kinetics of PEO in poly(ethylene terephthalate)–poly(ethylene oxide) segmented copolymers. I. Effect of the soft‐block length

The isothermal crystallization kinetics of poly(ethylene oxide) (PEO) block in two poly(ethylene terephthalate) (PET)–PEO segmented copolymers was studied with differential scanning calorimetry. The Avrami equation failed to describe the overall crystallization process, but a modified Avrami equation, the Q equation, did. The crystallizability of the PET block and the different lengths of the PEO block exerted strong influences on the crystallization process, the crystallinity, and the final morphology of the PEO block. The mechanism of nucleation and the growth dimension of the PEO block were different because of the crystallizability of the PET block and the compositional heterogeneity. The crystallization of the PEO block was physically constrained by the microstructure of the PET crystalline phase, which resulted in a lower crystallization rate. However, this influence became weak with the increase in the soft‐block length. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 3230–3238, 2000     

Competition Between Interfacial Interaction and Microphase Separation in Crystallization of Filled Block Copolymers

Understanding the effect of repulsive interaction between blocks on crystallization in block copolymers is beneficial for the design and development of sophisticated nanostructures. Dynamic Monte Carlo simulations were performed to reveal the crystallization mechanism of block copolymers containing one‐dimensional nanofiller under different repulsive interaction strengths between crystallizable and noncrystallizable blocks. During crystallization, crystalline morphology is determined by the competition between segmental orientation perpendicular to microphase interfaces dominated by microphase separation and that along the direction of the long axis of the nanofiller controlled by interfacial interaction. As the repulsive interaction between different blocks is strengthened, the competition between microphase separation and interfacial interaction is intensified, eventually leading to an increase in crystallization rate and a degradation in crystalline morphology. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1516–1526     

液晶嵌段共聚物PET/60PHB-b-PC的合成及结构与性能

采用ＰＥＴ齐聚物的原位乙酰化法通过加入少量乙二醇（ＥＧ）合成了端羟基液晶聚合物ＰＥＴ／６０ＰＨＢ，并将其作为大单体，与双酚Ａ及碳酸二苯酯通过熔融酯交换法，进一步制得了液晶嵌段共聚物ＰＥＴ／６０ＰＨＢ ｂ ＰＣ．研究了合成规律，并借助粘度测定、ＤＳＣ、偏光显微镜、Ｘ 光衍射和红外光谱分析等手段对合成的液晶嵌段共聚物进行了表征．研究表明，当ＰＥＴ齐聚物的ηｉｎｈ＝００５～００７ｄＬ／ｇ，Ａｃ２Ｏ／ＰＨＢ（ｍｏｌ／ｍｏｌ）＝１３，ＥＧ／ＰＥＴ（ｍｏｌ／ｍｏｌ）＝００６时能获得颜色、液晶性、溶解性均很好的端羟基液晶聚合物ＰＥＴ／６０ＰＨＢ，以此液晶聚合物为原料，采用合适的配方与工艺，能获得粘度较高、液晶性较好，并且熔体流动性很好的液晶嵌段共聚物ＰＥＴ／６０ＰＨＢ ｂ ＰＣ．通过偏光显微镜与Ｘ 光衍射观察，证明此嵌段共聚物呈现向列型液晶织构，但其液晶态织构与纯ＰＥＴ／６０ＰＨＢ、ＰＥＴ／６０ＰＨＢ和ＰＣ的混合物明显不同．此外，还初步建立了用红外的分析手段鉴定液晶聚合物ＰＥＴ／６０ＰＨＢ端基的方法．     

Nucleation and crystallization of H-shaped (PS)2PEG(PS)2 block copolymers

<正>A series of H-shaped(PS)_2PEG(PS)_2 block copolymers with different PS chain lengths were prepared.The influence of different confinements active on the crystallization and self-nucleation(SN) behavior of the PEG blocks was investigated by differential scanning calorimetry(DSC).When the content of the crystalline block was high,a classical SN behavior was obtained.The block copolymer with PEG content of 49%(by weight) showed a classical SN behavior with a narrow self-nucleation domain and had bimodal crystallization exotherms.When the PEG dispersed as separated microdomains in the block copolymer,the self-nucleation domain disappeared and only annealing was observed.     

Fast Crystallization and Toughening of Poly(<Emphasis Type="Italic">L</Emphasis>-lactic acid) by Incorporating with Poly(ethylene glycol) as a Middle Block Chain

High molecular weight poly(L-lactic acid)-poly(ethylene glycol)-poly(L-lactic acid) (PLLA–PEG–PLLA; PLGL) triblock copolymers with various lengths of the PLLA blocks were synthesized by ringopening polymerization of L-lactide. The amorphous and crystalline PLLA and PLGL films were prepared by hot pressing with different temperature treatments. PLLA and PEG blocks exhibited good miscibility in the amorphous PLGL samples, while phase separation occurred in the crystalline ones. The flexible PEG blocks not only accelerated the crystallization rate of PLLA but also greatly improve its flexibility. The crystallization time of PLGL copolymers shorten to less than 5 min and copolymers showed much better flexibility than neat PLLA, the maximum fracture strain reached about 600% for amorphous sample. The processing time of PLLA was greatly shortened and the brittleness of material was improved.     

Nucleation and crystallization of PS-b-PEO-b-PCL triblock copolymers

We have recently prepared a series of Polystyrene-b-Poly(ethylene oxide)-b-Polycaprolactone (PS-b-PEO-b-PCL or SEOCL) triblock copolymers of varying compositions and molecular weights. These ABC triblock copolymers present the peculiarity that two of the three blocks are able to crystallize upon cooling from an already phase segregated melt. When either of the crystallizable blocks or both are a minor phase, a fractionated crystallization process develops. The confinement of crystallizable blocks in the nanoscopic scale enables the clear observation in some cases of exclusive crystallization from homogeneous nuclei of two components within the triblock copolymer. The homogeneous nature of the nucleation was deduced since the supercooling attained is the maximum possible before vitrification of the material takes place. The self-nucleation domains were also found to depend on the composition and molecular weight of the copolymers. The block copolymers exhibited a marked decrease in crystalline memory and when the crystallizable blocks constitute minor phases, the self-nucleation domain disappears. The reason behind this behavior is that only at lower self-nucleation temperatures the density of self-nuclei becomes high enough to include at least one crystal fragment per confined microdomain in view of their vast numbers (e.g., 10¹⁶/cm³).     

The crystallization characteristics of ethylene block copolymers

Block copolymers of ethylene and butadiene with short ethylene sequences and degrees of polymerization up to 250 have been studied calorimetrically to determine their structure in the melt and also on crystallization. Crystallization rate characteristics and the thermodynamic parameters of the melting of block copolymers were studied. Block copolymers with ethylene sequences with degrees of polymerization below 20–30 were amorphous. Those with ethylene sequences of 35–45 units crystallized with extended chain crystals; above 45 units the polyethylene blocks crystallized with chain folding. There was a corresponding reduction in the melting point of the crystals and in the surface free energy of the crystals. The extent of crystallinity that developed within the copolymers was dependent on crystallization temperature and independent of time. This behavior was unlike that exhibited by polyethylene samples of similar molecular weight and was considered due to the effect of phase separation of the two blocks in the melt and nucleation control of the crystallization of the isolated domains. Analogous behavior was observed with polyethylene for polymer blends with polystyrene.     

Polycaprolactone-based block copolymers. II. Morphology and crystallization of copolymers of styrene or butadiene and ε-caprolactone

Three series of amorphous semicrystalline poly(styrene-b-ε-caprolactone)s have been synthesized with polystyrene blocks of 6000 (series A), 40000 (series B), and 70000 (series C) molecular weight, respectively. In these materials, the polymer miscibility evolves from a situation where a diffuse interphase involves the major part of the volume of the copolymer (series A) to a sharp phase separation as observed for copolymers with the longest PS block (series C). The crystallization of PCL blocks is mainly governed by the phase morphology. In copolymers of series A, the crystallization rate of PCL blocks is slowed down the more as the miscibility with PS increases, and ultimately the degree of crystallinity X_c decreases significantly. When phase separation is sharp, X_c changes dramatically at the phase inversion and decreases when PS forms the continuous phase. At the inversion X_c depends on the mean size of the PCL microdomains as compared with the thickness of the crystalline lamellae. The periodicity of the phase morphology as observed by TEM is influenced by the solvent used in casting films, whereas monolamellar monocrystals can be obtained by a self-seeding technique.     

聚氧化乙烯-聚苯乙烯-聚氧化乙烯三嵌段共聚物的微相分离与结晶

本工作研究了多分散和单分散聚氧化乙烯-聚苯乙烯-聚氧化乙烯三嵌段共聚物(PEO-PS-PEO)的结晶行为,及这些试样按非晶型嵌段共聚物进行微相分离后再结晶的结晶特点.     

Thermal fractionation of vinyl acetate-vinyl alcohol copolymers

Thermal fractionation via the method of successive self-nucleation and annealing was used for the first time to study the crystallinity of vinyl acetate-vinyl alcohol copolymers with different random distributions of chain units. The lamella-thickness distribution was calculated through the Gibbs-Thomson equation. It was shown that, for all samples, the minimum lamella thickness is the same and corresponds to a block of no less than 15 vinyl alcohol units. On the basis of these data and with the use of the computer simulation of the polymer-analogous reaction via the Monte Carlo method, the block-length distribution in the crystalline phase was found. It was shown through a comparison of the lamella-thickness and block-length distributions that the maximum lamella thickness increases with the block length and vinyl alcohol content in the copolymer. In crystallites, blocks with lengths exceeding the maximum lamella thickness comprise a significant fraction. Thus, it is probable that these blocks form folds. The dependences of melting temperatures of crystalline lamellas on their thicknesses, as well as the dependences of the melting temperatures of copolymers not subjected to thermal fractionation on the chain-structure parameters, are adequately described by the Flory crystallization theory.     

Block copolymers of poly(ethylene terephthalate–polybutylene terephthalate). I. Preparation and crystallization behavior

Block copolymers of two crystallizable compounds, poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT), were developed with PET as the major component and the amount of PBT varying from 1.0 to 20.0 wt %. These block copolymers were prepared by end-group coupling of preformed oligomers. All polymers prepared were of equivalent molecular weight as determined by the intrinsic viscosity method. Thermal properties were determined by differential thermal analysis (DTA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). With increasing PBT content, the block copolymers showed a general decrease in the values of glass transition temperature, melting temperature, initial decomposition temperature, and maximum decomposition temperature. The heat of fusion and heat of crystallization first increased and then decreased slightly. Rates of crystallization were determined by measuring density as a function of time of isothermal crystallization carried out at 95°C. It was found that small amounts of PBT increased the crystallization rate considerably over that of PET. Random copolymers did not show this phenomenon and behaved more like pure PET. The crystallization behavior of block copolymers was analyzed by the Avrami equation and Avrami exponents were determined. Results were explained on the basis that the faster-crystallizing PBT blocks crystallized first and provided built-in nucleation sites for the subsequent crystallization of PET, thus resulting in a relatively fast-crystallizing copolyester.     

Confinement Effects on the Crystallization Kinetics and Self-Nucleation of Double Crystalline Poly(p-dioxanone)-b-poly(ϵ-caprolactone) Diblock Copolymers

The morphology, crystallization and self nucleation behavior of double crystalline diblock copolymers of poly(p-dioxanone) (PPDX) and poly(ϵ-caprolactone) (PCL) with different compositions have been studied by different techniques, including optical microscopy (OM), atomic force microscopy (AFM) and differential scanning calorimetry (DSC). The two blocks crystallize in a single coincident exotherm when cooled from the melt. The self-nucleation technique is able to separate into two exotherms the crystallization of each block. We have gathered evidences indicating that the PPDX block can nucleate the PCL block within the copolymers regardless of the composition. This effect is responsible for the lack of homogeneous nucleation or fractionated crystallization of the PCL block even when it constitutes a minor phase within the copolymer (25% or less). Nevertheless, we were able to show that decreasing amounts of PCL within the diblock copolymer still produces confinement effects that retard the crystallization kinetics of the PCL component and decrease the Avrami index. On the other hand evidence for confinement was also obtained for the PPDX block, since as its content is reduced within the copolymer, a depression in its self-nucleation and annealing temperatures were observed.     

聚芳醚酮与液晶聚酯多嵌段共聚物的合成表征

近年来,以热塑性聚合物为基体,热致液晶聚合物(TLCP)作为增强剂的高分子原位复合材料由于其具有优异的机械性能和优良的成型加工性能,已引起各国工作者的普遍关注和极大兴趣．然而由于自聚集和相分离作用的影响,大部分液晶聚合物与通常的热塑性聚合物基体基本不相容或弱相容,这对于提高原位复合材料的力学性能不利．     

聚苯乙烯-b-聚2(5)-乙烯基对(间)苯二甲酸二钠嵌段共聚物的合成及其对PET结晶行为的影响

通过原子转移自由基聚合合成了线形及三臂聚苯乙烯-b-聚2(5)-乙烯基对(间)苯二甲酸二钠嵌段共聚物,通过凝胶渗透色谱、核磁共振和热失重表征证实得到了结构明确、分散度较窄的嵌段共聚物成核剂.采用熔融共混的方法制得聚对苯二甲酸乙二酯(PET)与成核剂共混样品.采用差示扫描量热仪与一维X射线衍射仪研究了PET及添加成核剂后...     

聚对苯二甲酸乙二醇酯/聚乙二醇醚插层嵌段共聚物的结晶性能

合成了不同用量、不同分子量的聚乙二醇醚(PEG)或聚丁二醇醚(PTMC)与聚对苯二甲酸乙二醇酯(PET)/蒙脱土(MMT)的嵌段共聚物。研究了MMT在共聚物中的分散状态及PEG或PTMG对PET/MMT插层聚合物结晶性能的影响。结果表明,MMT在共聚物中以纳米尺寸分散;加入PEG或PTMG增强了聚酯链段的柔顺性,使共聚物熔体降温过程的结晶温度提高,冷结晶温度降低,即插层嵌段共聚物的结晶速率提高;在合成的共聚物中,分子量为2000,用量为DMT的6%的PEG对插层共聚物结晶速率的促进作用最大