Reaction‐Induced Liquid Crystalline Polybenzoxazine Bearing Aromatic Amide Side Branches

Abstract

AbstractIn this study, a nematic phase structure is incorporated into polybenzoxazine to increase its thermal conductivity. A simple route for the synthesis of a thermally conductive polybenzoxazine containing liquid crystalline (LC) structure by grafting oligomeric p‐sulfophenylene‐terephthalamide (PSTA) is offered. Benzoxazine monomer of pHBA‐da is synthesized via Mannich reaction of p‐hydroxy benzoic acid, p‐formaldehyde, and dodecyl amine. After ring‐opening polymerization, the oligomer benzoxazine of OBZ─COOH is obtained. The OBZ─COOH/PSTA mixture is prepared by mixing PSTA with OBZ─COOH. Afterward, the grafted copolymer is named OBZ─PSTA copolymer. The liquid crystalline behavior of OBZ─COOH/PSTA is studied by polarized optical microscopy and small angle X‐ray scattering analysis. The results show that the OBZ─PSTA forms the LC structure during isothermal and non‐isothermal curing. The LC structure displays a floral textured nematic phase. The phase formation is induced by an amidation reaction. Due to the grafts of LC PSTA, the thermal conductivity of OBZ─PSTA is 0.296 W m−1 K−1, which is 26% greater than OBZ─COOH. The glass transition temperature (Tg) of OBZ─PSTA is 241 °C. The 5% (Td5) and 10% weight loss temperatures (Td10) of OBZ─PSTA are 346 and 362 °C, respectively.