Composition-dependent phase transformation in side-chain liquid crystalline copolymers with mesogenic groups at different substituent positions
Composition-dependent phase transformation in side-chain liquid crystalline copolymers with mesogenic groups at different substituent positions
复制标题
不同取代基位置具有介晶基团的侧链液晶共聚物中的组成依赖性相变
DOI：
10.1039/d1sm00161b
复制
发表时间：
2021
期刊：
影响因子：
3.4
通讯作者：
Chen Xiao-Fang
中科院分区：
文献类型：
--
作者：
Pei Jiwei;Wei Wenjing;Li Bian;Chen Xiao-Fang
共聚是调整液晶聚合物材料热性能和结构性能的一种有效方法，在各种应用中是必不可少的。本工作通过开环歧化聚合合成了两个系列的聚降冰片烯共聚物A-r-B和A-r-C，它们的联苯基介晶侧基位于不同的取代基位。相应的均聚物A和C是液晶聚合物，分别表现为斜柱状结构(Colob/p2)和片层结构，而均聚物B为非晶态。结合SAXS、GISAXS、AFM、DSC和POM等技术，系统地研究了共聚物的组成相关相行为。随着A(XA)摩尔分数的增加，共聚物A-r-B的自组织结构由无定形到片层、波状片层和Colob/p2结构，A-r-C的自组织结构依次为片层、波状片层和Colob/p2结构。然后，具有波状片层或Colob/p2结构的共聚物在较高的温度下倾向于首先进入片层相，然后在加热过程中转变为各向同性状态。组成诱导的从片层到超分子柱状组织的转变多少让人想起嵌段共聚物和其他可以形成有序结构的软物质体系。此外，刚性介晶单元在侧链上的取代数目和位置可以进一步改变自组织相的形态。
Copolymerization is an effective approach to tailor the thermal and structural properties of liquid crystalline polymer materials, which is essential for various applications. In this work, two series of polynorbornene copolymers, A-r-B and A-r-C, with the biphenyl mesogenic side group at different substituent positions were synthesized via ring-opening metathesis polymerization in various compositions. The corresponding homopolymers A and C are liquid crystalline polymers, exhibiting an oblique columnar structure (Colob/p2) and lamellar structure, respectively, while homopolymer B is amorphous. The composition-dependent phase behaviors of copolymers were systematically studied with the combination of SAXS, GISAXS, AFM, DSC and POM techniques. With increasing molar content of A (xA), the self-organzied structure of copolymer A-r-B follows the sequence from amorphous to lamellar, undulated lamellar, and Colob/p2 structures, and that of A-r-C follows the sequence of lamellar, undulated lamellar, and Colob/p2 structures. Then, copolymers with undulated lamellar or Colob/p2 structures tend to enter lamellar phase first at higher temperature and then change to the isotropic state during heating. The composition-induced transition from lamellar to supramolecular columnar organization is somewhat reminiscent of block copolymers and other soft matter systems that can form ordered structures. Furthermore, the subsitituent number and position of rigid mesogenic units in the side chain can further modify the morphologies of self-organized phases.