Cross-linked liquid crystalline polybenzoxazines bearing cholesterol-based mesogen side groups

A cross-linked liquid crystalline polybenzoxazine [poly(BA-ac)] was synthesized for the first time from a novel bifunctional benzoxazine monomer (BA-ac) containing cholesterol-based mesogens. The monomer was synthesized using cholesteryl 4-aminobenzoate, bisphenol-A, and paraformaldehyde as raw materials via Mannich reaction. Subsequently, the cross-linked polybenzoxazine bearing cholesterol-based mesogen side groups was obtained through thermally induced ring-opening polymerization of the benzoxazine ring. The study results show that BA-ac is a monotropic smectic C liquid crystal, and poly(BA-ac) contains a smectic C phase structure. The formation of the liquid crystalline structure of poly(BA-ac) is mainly caused by the strong ability of cholesterol-based mesogen to form liquid crystals and its position on the side group of the cross-linked network. Due to the existence of a liquid crystal structure, poly(BA-ac) has high thermal conductivity. Its coefficient of thermal diffusivity is 31% higher than that of a traditional polybenzoxazine poly(BA-a). Poly(BA-ac) also has high heat-resistance. Its glass transition temperature, 5% and 10% weight loss temperatures are 175 degrees C, 306 degrees C, and 321 degrees C, respectively. (C) 2018 Elsevier Ltd. All rights reserved.