聚氧化乙烯-聚苯乙烯-聚氧化乙烯三嵌段共聚物/聚苯醚共混物的相容性和结晶行为

 本工作对聚氧化乙烯-聚苯乙烯-聚氧化乙烯(PEO-PS-PEO)三嵌段共聚物与聚苯醚(PPO)均聚物共混物的相容性及结晶行为进行了研究。结果表明,共混体系的相容性与嵌段共聚物中苯乙烯段的含量有关,PS含量越高,PPO与共聚物PS段的相容性越好。共混体系的结晶行为也明显不同于一般均聚物共混体系。在DSC降温结晶过程中最多可出现三个结晶峰。     

聚氧化乙烯-聚苯乙烯-聚氧化乙烯三嵌段共聚物/聚苯醚共混物的相容性和结晶行为

本工作对聚氧化乙烯-聚苯乙烯-聚氧化乙烯(PEO-PS-PEO)三嵌段共聚物与聚苯醚(PPO)均聚物共混物的相容性及结晶行为进行了研究。结果表明,共混体系的相容性与嵌段共聚物中苯乙烯段的含量有关,PS含量越高,PPO与共聚物PS段的相容性越好。共混体系的结晶行为也明显不同于一般均聚物共混体系。在DSC降温结晶过程中最多可出现三个结晶峰。     

微量聚四氢呋喃-聚甲基丙烯酸甲酯/聚四氢呋喃共混体系稀固体溶液中共聚物胶束的抑制成核作用

 本工作将Leibler、Whitmore和Mayes等近期关于非晶嵌段共聚物共混体系胶束理论应用于结晶嵌段共聚物共混体系的熔融态,对聚甲基丙烯酸甲酯-聚四氢呋喃两嵌段共聚物与聚四氢呋喃均聚物共混体系的结晶行为进行了研究.结果表明,很低的共聚物浓度(如1％),其胶束在共混体系的结晶过程中即可显著地起到抑制成核的作用.这对改善结晶均聚物的形态及性能有一定的应用价值.     

聚甲基丙烯酸甲酯－聚四氢呋喃两嵌段共聚物／聚四氢呋喃共混体系的相容性和结晶行为

报道了对嵌段共聚物结晶型共混体系结晶行为的研究．通过对聚甲基丙烯酸甲酯－聚四氢呋喃两嵌段共聚物／聚四氢呋喃共混体系的研究，我们发现１．微相分离结构的存在，可使相容的这类体系形成多种特殊的结晶形态；２．共混体系的相容性可以方便地由其结晶行为来判断；３．共混体系中共聚物的结晶能力显著提高．这些特点都明显不同于一般的聚合物共混体系．     

微量聚四氢呋喃-聚甲基丙烯酸甲酯/聚四氢呋喃共混体系稀固体溶液中共聚物胶束的抑制成核作用

本工作将Leibler、Whitmore和Mayes等近期关于非晶嵌段共聚物共混体系胶束理论应用于结晶嵌段共聚物共混体系的熔融态,对聚甲基丙烯酸甲酯-聚四氢呋喃两嵌段共聚物与聚四氢呋喃均聚物共混体系的结晶行为进行了研究.结果表明,很低的共聚物浓度(如1％),其胶束在共混体系的结晶过程中即可显著地起到抑制成核的作用.这对改善结晶均聚物的形态及性能有一定的应用价值.     

PMMA—b—PTHF／PTHF共混体系中共聚物结晶能力的增强

结晶嵌段共聚物具有一般均聚物所没有的许多特殊结晶行为。虽然,人们很早就已开始对聚氧化乙烯/聚苯乙烯诸类嵌段共聚物的结晶行为进行研究,但对这类体系相分离规律及结晶行为的认识仍很不够。这主要是因为已研究的体系非常有限,此外,大都为对体系非平衡态结构的研究。所以,尽管Whitmore和Noolandi最近提出了结晶嵌段共聚物及其共混物的平衡形态理论,但缺乏实验数据与之比较。     

微量PEO-PS-PEO/PEO共混体系结晶过程中共聚物胶束的成核作用

本工作将Leibler等近期关于含非晶两嵌段共聚物“稀固体溶液”的胶束理论推广并应用到含结晶三嵌段共聚物的“稀固体溶液”.对微量聚氧化乙烯-聚苯乙烯-聚氧化乙烯三嵌段共聚物/聚氧化乙烯均聚物共混体系的结晶行为进行了研究.结果表明,共聚物胶束在共混体系的结晶过程中可以起到成核剂的作用.这对改善结晶均聚物的性能具有一定的应用价值.     

在含嵌段共聚物的“稳固体溶液”中决定共聚物胶束作用的诸因素

 在含嵌段共聚物可结晶型“稀固体溶液”的结晶过程中,我们已发现共聚物胶束既可起着成核剂的作用,也可起抑制成核数目的作用.本文根据进一步的研究结果,论述了共聚物胶束是起着成核剂的作用,还是起抑制成核作用或对体系的成核行为无影响主要取决于共聚物和均聚物的相对结晶能力及共混体系的相容性.     

聚苯乙烯溶胀聚苯乙烯－聚丁二烯－聚苯乙烯三嵌段共聚物微区的研究

嵌段共聚物/均聚物共混体系,各嵌段会形成各自的相,并且嵌段间的连接点一定在两相之间的界面上,这一要求极大地影响了嵌段共聚物/均聚物共混体系的链构象和相行为.     

在含嵌段共聚物的“稳固体溶液”中决定共聚物胶束作用的诸因素

在含嵌段共聚物可结晶型“稀固体溶液”的结晶过程中,我们已发现共聚物胶束既可起着成核剂的作用,也可起抑制成核数目的作用.本文根据进一步的研究结果,论述了共聚物胶束是起着成核剂的作用,还是起抑制成核作用或对体系的成核行为无影响主要取决于共聚物和均聚物的相对结晶能力及共混体系的相容性.     

COMPUTER SIMULATION OF MISCIBILITY AND SELF-ASSEMBLY STRUCTURE FOR POLYMER-CONTAINING SYSTEMS WITH SPECIAL INTERACTIONS

The miscibility and structure of A-B copolymer/C homopolymer blends with special interactions were studied by aMonte Carlo simulation in two dimensions. The interaction between segment A and segment C was repulsive, whereas it wasattractive between segment B and segment C. In order to study the effect of copolymer chain structure on the morphologyand structure of A-B copolymer/C homopolymer blends, the alternating, random and block A-B copolymers were introducedinto the blends, respectively. The simulation results indicated that the miscibility of A-B block copolymer/C homopolymerblends depended on the chain structure of the A-B copolymer. Compared with alternating or random copolymer, the blockcopolymer, especially the diblock copolymer, could lead to a poor miscibility of A-B copolymer/C homopolymer blends.Moreover, for diblock A-B copolymer/C homopolymer blends, obvious self-organized core-shell smicture was observed inthe segment B composition region from 20% to 60%. However if diblock copolymer composition in the blends is less than40%, obvious self-organized core-shell structure could be formed in the B-segment component region from 10 to 90%.Furthermore, computer statistical analysis for the simulation results showed that the core sizes tended to increasecontinuously and their distribution became wider with decreasing B-segment component.     

CRYSTALLIZATION OF BLENDS OF AN ASYMMETRIC POLY（OXYETHYLENE）-b-POLY（OXYBUTYLENE） BLOCK COPOLYMER WITH POLY（OXYBUTYLENE）

An oxyethylene/oxybutylene block copolymer with asymmetric volume fraction (E115B103) was blended with oxybutylene homopolymer (Bh) at different volume fractions of the block (φE). Crystallization behavior of the blends was studied and was compared with that of the blends from a symmetric block copolymer (E114B56). It was found that the crystallization temperature of E115B103/B28 blend is lower than that of the blends from symmetric block copolymer. For the blend with φE= 0.30 breakout crystallization with an Avrami exponent n ≈ 3.0 is observed. At φE = 0.22 the blend exhibits a variable crystallization behavior: confined crystallization with n ≈ 1.0 at lower crystallization temperatures but breakout crystallization at high crystallization temperatures. For the blend with φE = 0.14 and sphere morphology confined crystallization occurs at all crystallization temperatures studied. When compared with the blends from symmetric block copolymer, confined crystallization occurs more easily in the E115B103/B28 blends. The SAXS results agree with the isothermal crystallization kinetics. Deformation of the confined crystalline block is observed in the blend with φE = 0.14 and mixed lamellar and cylinder morphologies in the blend with φE = 0.22.     

Dissipative particle dynamics study on the interfaces in incompatible A/B homopolymer blends and with their block copolymers

Dissipative particle dynamics, a simulation technique appropriate at mesoscopic scales, has been applied to investigate the interfaces in immiscible binary A/B homopolymer blends and in the ternary systems with their block copolymers. For the binary blends, the interfacial tension increases and the interface thickness decreases with increasing Flory-Huggins interaction parameter chi while the homopolymer chain length is fixed. However, when the chi parameter and one of the homopolymer chain length is fixed, increasing another homopolymer chain length will induce only a small increase on interfacial tension and slight decrease on interface thickness. For the ternary blends, adding the A-b-B block copolymer will reduce the interfacial tension. When the mole number of the block copolymer is fixed, longer block chains have higher efficiency on reducing the interfacial tension than the shorter ones. But for the block copolymers with fixed volume fraction, shorter chains will be more efficient than the longer ones on reducing the interfacial tension. Increasing the block copolymer concentration reduces interfacial tension. This effect is more prominent for shorter block copolymer chains.     

Influence of Phase Separation Behaviour on Toughness of Compression Moulded SBS Star Block Copolymer/Polystyrene Blends

The influence of homopolymer molecular weight and compression moulding on morphology formation and deformation behaviour of binary blends of polystyrene-polybutadiene based star block copolymer and polystyrene (PS) homopolymer was investigated. The samples used were a polystyrene-(polystyrene-co-polybutadiene)-polystyrene (S-S/B-S) star block copolymer and anionically prepared polystyrene (aPS). The techniques used were transmission electron microscopy (TEM) and uniaxial tensile testing. A wide range of segregation behaviour was observed depending on the ratio of the length of aPS chains relative to that of corresponding outer blocks of the block copolymer. For the first time, the formation of macrophase-separated ‘droplet-like’ morphology has been reported, which endows the block copolymer/polystyrene blends with higher toughness. The mechanical properties of blends are discussed in the light of micromechanical processes of deformation. The micromechanical mechanisms and their dependence with inter domain distance are similar to the mechanisms found in rubber network toughened systems.