The liquid-crystalline (LC) phase structures and transitions of a combined main-chain/side-chain LC polymer (MCSCLCP) 1 obtained from radical polymerization of a 2-vinylterephthalate, poly(2,5-bis{[6-(4-butoxy-4'-oxybiphenyl) hexyl]oxycarbonyl}styrene), were studied using differential scanning calorimetry, one- and two-dimensional wide-angle X-ray diffraction (1D and 2D WAXD), and polarized light microscopy. We have found that 1 with sufficiently high molecular weight can self-assemble into a hierarchical structure with double orderings on the nanometer and subnanometer scales at low temperatures. The main chains of 1, which are rodlike as a result of the "jacketing" effect generated by the central rigid portion of the side chains laterally attached to every second carbon atom along the polyethylene backbone, form a 2D centered rectangular scaffold. The biphenyl-containing side chains fill the space between the main chains, forming a smectic E (SmE)-like structure with the side-chain axis perpendicular to that of the main chain. This biaxial orientation of 1 was confirmed by our 2D WAXD experiments through three orthogonal directions. The main-chain scaffold remains when the SmE-like packing is melted at elevated temperatures. Further heating leads to a normal smectic A (SmA) structure followed by the isotropic state. We found that when an external electric field was applied, the main-chain scaffold greatly inhibited the motion of the biphenyls. While the main chains gain a sufficiently high mobility in the SmA phase, macroscopic orientation of 1 can be achieved using a rather weak electric field, implying that the main and side chains with orthogonal directions can move cooperatively. Our work demonstrates that when two separate components, one offering the "jacketing" effect to the normally flexible backbone and the other with mesogens that form surrounding LC phases, are introduced simultaneously into the side chains, the polymer obtained can be described as an MCSCLCP with a fascinating hierarchically ordered structure.

A series of hairy‐rod polymers, poly{2,5‐bis[(4‐alkoxyphenyl)oxycarbonyl]styrenes} (P‐OCm, m = 1, 2, 4, 6, 8, 10, 12, 14, 16, and 18) were designed and successfully synthesized via free radical polymerization. The chemical structure of the monomers was confirmed by elemental analysis, 1H NMR and 13C NMR. The molecular characterizations of the polymers were performed with 1H NMR and gel permeation chromatography. The phase structures and transitions of the polymers were investigated by the combination of techniques including differential scanning calorimetry, wide‐angle X‐ray diffraction, polarized optical microscopy, and rheological measurement. The experimental results revealed that the self‐assembly behaviors of P‐OCm changed with the increase in m. First, the P‐OCm (m = 1, 2) showed only a stable liquid crystalline phase above Tg. Second, with the increasing length of alkoxy tails, the P‐OCm (m = 4, 6, 8) presented a re‐entrant isotropic phase above Tg and a liquid crystalline phase at higher temperature. Third, the P‐OCm (m = 10, 12, 14, 16, 18) exhibited an unusual re‐entrant isotropic phase which was separating SmA (in low temperature) and columnar phases (in high temperature). It was the first time that mesogen‐jacketed liquid crystalline polymers formed smectic phase, re‐entrant isotropic phase, and columnar phases in one polymer due to the microphase separation and the driving force of the entropy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012