Effects of Mesogenic Shape and Flexibility on the Phase Structures of Mesogen-Jacketed Liquid Crystalline Polymers with Bent Side Groups Containing 1,3,4-Oxadiazole

Abstract

We report the design, synthesis, and characterization of a new series of mesogen-jacketed liquid crystalline polymer (MJLCP) with rigid bent-core side groups and different flexible tails. The structures of monomers of 3,5-bis[(4-alkoxy-phenyl)-1,3,4-oxadiazole]styrene (MCx, x is the number of carbons in the alkoxy groups, x = 4, 6, 8, 10, 12, 14, 16, and t for tert-butyl) were confirmed by 1H NMR, mass spectrometry, IR, and elemental analysis. Basic characterizations of polymers were performed with 1H NMR and gel permeation chromatography. The phase transition and structures of polymers were investigated via differential scanning calorimetry, wide-angle X-ray diffraction, and polarized light microscopy experiments. Hexagonal column (ΦH) liquid crystalline phases with long-range order on a length scale of 3−5 nm and short-range order of 0.5 nm were observed in all PCx while monomers had no liquid crystallinity. The flexible alkoxy side groups of polymer rods interpenetrated with others except for rigid tert-butyl groups. Compared with the reported work in our group, a change in substitute position resulted in totally different packing of both monomers and polymers. Namely, both the molecular shape and the flexibility may greatly affect the packing behaviors of polymers and thus their liquid crystalline phase structures.