In situ sol–gel synthesis of silica reinforced polybenzoxazine hybrid materials with low surface free energy

Abstract

In the present work, silica reinforced polybenzoxazine (PBZ–SiO₂) hybrid materials possessing low surface free energy have been developed using a dimethylol-functional benzoxazine monomer (4HBA-BZ), tetraethoxysilane (TEOS) and 3-(isocyanatopropyl)triethoxysilane (ICPTS) through an in situ sol–gel process. Data from the contact angle measurement indicate that the hybrid materials are hydrophobic in nature and possess a low surface free energy. For example, a PBS₃ hybrid material (1 : 1 : 1 ratio of 4HBA-BZ : ICPTS : TEOS) exhibits a low surface free energy of 18.6 mJ m⁻² which is lower than that of poly(tetrafluoroethylene) (22.0 mJ m⁻²). Further data obtained from thermal studies indicate that the hybrid PBZ possesses higher values of the glass transition temperature (T_g), thermal stability and char yield than those of neat PBZ.