Precise synthesis and surface wettability of a polymer with liquid crystalline side chains

Well-defined poly(methacrylate)s with liquid crystal side chains, designated as PPHM, were synthesized by a living anionic polymerization method. Introducing a short-length alkyl chain at the end of the side chain, the solubility of the polymer was improved, resulting in higher molecular weight polymers. While the highest weight-average molecular weight (M_w) of PPHM was 68k, it exceeded 100k for a slight-polydisperse PPHM. Wide-angle X-ray diffraction (WAXD) revealed that PPHM formed a smectic A phase with 2.7 nm layer spacing and that the layer structure is present even in the glassy state at room temperature. Molecular aggregation states of PPHM in surface regions of films were characterized by sum-frequency generation, grazing-incidence WAXD, and contact angle measurements. The results show that the PPHM with a larger M_w formed a layer structure parallel to the film plane. Although low M_w PPHM also maintained a layer structure, the structure became more random within internal regions. The surface reorganization of PPHM with larger M_w was suppressed in comparison with smaller ones.