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Side-Chain Jacketed Liquid Crystalline Polymer Forming Double-Chain Supramolecular Column and Hexagonal Superlattice

Zheng, Jun-Feng, Yu, Kai-Ling, Jiang, Xu-Qiang, Tang, Tao, Sun, Jia, Ding, Lin-Lin, Zhang, Rui, Zhao, Yang, Ren, Xiang-Kui, Xu, Jia-Ru, Zhang, Yan-Fang, Yu, Xiao-Song, Yang, Shuang, Chen, Er-Qiang
Macromolecules 2018 v.51 no.17 pp. 6949-6957
X-ray diffraction, isomers, light microscopy, liquids, melting, moieties, polyethylene, thermal analysis
We synthesized a series of poly(dialkyl 1-viny-3,5-isophthalate) (P₃,₅-n, n is the number of carbons on alkyl group, n = 4–18), wherein the polyethylene backbone is jacketed by the isophthalate side chains. The phase behaviors of P₃,₅-n were investigated by using various techniques including thermal analysis, polarized light microscopy, and X-ray diffraction. It is identified that with n ≥ 8 the P₃,₅-n samples form the hexagonal columnar phase (ΦH). Furthermore, P₃,₅-16 and P₃,₅-18 can exhibit a four-column hexagonal superlattice (ΦHS), wherein one column is frustrated. After the alkyl tails are fully melted or crystallized, the ΦHS degrades into the conventional ΦH phase. For the ΦH of P₃,₅-n observed, the cross section area of the column (S) increases linearly with n, S = 1.97 + 0.52n (nm²). The number of repeating units (Zᵣₑₚ) required to be packed in the 0.44 nm thick column stratum is 4. Compared with poly(dialkyl 1-vinyl-2,5-terephthalate) (P₂,₅-n), which is the isomer of P₃,₅-n and can form the ΦH phase based on the parallel packing of a “single-chain column”, P₃,₅-n possesses the intercept and slope of the linear function of S vs n and the Zᵣₑₚ value nearly twice that found for P₂,₅-n. We propose that P₃,₅-n can self-organize into the column containing two chains laterally associated together. Namely, P₃,₅-n takes the “double-chain column” rather than the “single-chain column” as the building block for the ΦH phase.