Triphenylene-Based Side Chain Liquid Crystalline Block Copolymers Containing a PEG block: Controlled Synthesis, Microphase Structures Evolution and Their Interplay with Discotic Mesogenic Orders

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• 作者：Bin Wu ; Bin Mu ; Sai Wang ; Junfei Duan ; Jianglin Fang ; Rongshi Cheng ; Dongzhong Chen
• 刊名：Macromolecules
• 出版年：2013
• 出版时间：April 23, 2013
• 年：2013
• 卷：46
• 期：8
• 页码：2916-2929
• 全文大小：700K
• 年卷期：v.46,no.8(April 23, 2013)
• ISSN：1520-5835

文摘

Triphenylene (TP) derivatives are typical and probably the most widely studied discotic liquid crystalline (DLC) materials. Through polymer analogous reactions to attach TP mesogens to the well-synthesized poly(ethylene glycol)-b-poly(2-hydroxyethyl acrylate) (PEG鈥揚HEA) by ATRP, a series of well-defined side chain DLC diblock copolymers PEG鈥損oly(TPm) (m = 6 or 10) with DLC block weight fraction (f_w,DLC) ranging from 37% to 90% have been successfully prepared with narrow molecular weight distribution (PDI 鈮?1.11). An intriguing microphase-separated superstructure evolution and the correlation between overall morphologies and discotic mesogenic orders as a function of f_w,DLC and temperature have been demonstrated by combination of DSC, POM, and variable temperature SAXS/WAXS. Those copolymers with lower DLC contents (f_w,DLC = 37% and 43%) and at lower temperatures formed lamellar structures of variant periods and underwent order鈥搊rder transitions upon PEG region crystallization at 45 掳C and different discotic mesophases of N_D or N_col transition at about 25 掳C. For the copolymer with intermediate f_w,DLC = 62%, a high temperature hexagonal packed cylinder (HPC) structure of amorphous PEG nanocylinders in the matrix of DLC was formed above 35 掳C, while upon cooling below 35 掳C it turned into a mixed lamellar structure with PEG region crystallization. The higher f_w,DLC (67% 80%) copolymers exhibited HPC structures with the DLC matrix showing N_col or N_D mesophases. For copolymers with the highest f_w,DLC around 90%, an overall N_D phase was developed in sharp contrast to the ordered columnar phase formed by their corresponding DLC homopolymers, which was quite inspiring and might suggest another pathway of attaining this important nematic discotic phase through introducing a suitable copolymerized block. The better understanding of the interrelation of microstructures and discotic mesogenic orders constitutes the key basis for utilizing such type of organic semiconductor materials and could help to guide the design of complex DLC polymer materials with hierarchical structures for variant applications.