Side-Chain Liquid Crystalline Block Copolymers with Well Defined Structures Prepared by Living Anionic Polymerization IV. Microphase Morphology in Blends with Coil Homopolystyrenes
Side-Chain Liquid Crystalline Block Copolymers with Well Defined Structures Prepared by Living Anionic Polymerization IV. Microphase Morphology in Blends with Coil Homopolystyrenes
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活性阴离子聚合制备结构明确的侧链液晶嵌段共聚物IV．
DOI：
10.1295/polymj.33.783
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
J. Watanabe
中科院分区：
文献类型：
--
作者：
T. Itoh;N. Tomikawa;Masayuki Yamada;M. Tokita;A. Hirao;J. Watanabe
研究了液晶-线团嵌段共聚物与线团均聚物共混体系的微区结构。所用的LC-螺旋嵌段共聚物由作为LC链段的聚（甲基丙烯酸6-[4-（4 '-甲氧基苯基）苯氧基]己酯）和作为螺旋链段的聚苯乙烯组成。其分子量Mn=47000，LC链段分数为45wt%。作为卷曲均聚物，使用具有37000、26000和8200的不同分子量的三种聚苯乙烯。在所有的共混物与LC段分数为35%至10%，微相分离是清楚地认识到和LC段在所产生的微区进行定义明确的晶体SmA各向同性相变。共混物的微区结构不仅与均聚苯乙烯的分子量有关，而且与液晶链段的相结构有关。当Mn=37000的最高分子量聚苯乙烯共混时（所谓的“干刷”方式），即使组成和温度变化，也总是观察到层状类型的形态。相反，当使用Mn=8200的最低分子量聚苯乙烯时（在“湿刷”方案中），形态的类型显著改变。在液晶链段的各向同性温度下，当液晶含量为45%~ 35%时，共混物均为片层结构，但随着液晶含量的降低，片层结构以圆柱形或球形为主。另一方面，在结晶温度下通常观察到层状形态。因此，在某些低分子量液晶链段的共混物中，随着温度的降低，可以看到从球形或圆柱形到层状的有序-有序转变。这种形态转变是由倾向于垂直于微区界面取向的层状结构的形成引起的。结果表明，液晶链段的结构顺序影响均聚物在嵌段共聚物中的微区形态和溶解方式。
The microdomain structure in the blends of liquid crystal (LC)-coil block copolymer with coil homopolymers was studied. The LC-coil block copolymer used is composed of poly(6-[4-(4’-methoxyphenyl) phenoxy] hexyl methacrylate) as a LC segment and polystyrene as a coil segment. It has the molecular weight Mn=47000 with the LC segment fraction of 45 wt%. As a coil homopolymer, three polystyrenes with different molecular weights of 37000, 26000, and 8200 were used. In all the blends with LC segment fractions of 35% to 10%, the microphase segregation is clearly recognized and LC segment in resulting microdomain undergoes the well defined crystal-SmA-isotropic phase transitions. The microdomain structure depends on both the molecular weight of homopolystyrene blended and the phase structure of LC segment. When the highest molecular weight polystyrene with Mn=37000 was blended (so called in a “dry-brush” regime), a lamellar type of morphology is invariably observed even if the composition and temperature are varied. In contrast, when the lowest molecular weight polystyrene with Mn=8200 was used (in a “wet-brush” regime), the type of morphology is significantly altered. At the isotropic temperatures of LC segment, the lamellar morphology is observed for the blends with LC contents from 45% to 35%, but the cylindrical or spherical domain becomes predominant with a decrease in the LC content. On the other hand, the lamellar morphology is commonly observed at the crystal temperatures. In some blends with the lower weight fractions of LC segment, hence, there can be seen the order–order transition from sphere or cylinder to lamella on decreasing temperature. This morphological transformation is caused by the formation of the layered structure that tends to orient perpendicularly to the interface of microdomain. The results show that the structural order of LC segment affects both the microdomain morphology and the solubility style of the homopolymer into the block copolymer.