Low melting point, high thermal stable branched benzoxazines resin derived from mixed-substituted phosphazene core

Abstract

Six fluorine-containing, mix-substituted phosphazene-based branched benzoxazine monomers with a low melting point were successfully prepared and their chemical structures were verified by 1H, 13C, 31P and 19F nuclear magnetic resonance (NMR). These branched benzoxazine resins underwent thermal ring-opening polymerization to form cured polymers with high thermal stability both in N2 atmosphere and in air. The co-substituents, both m-CF3PhOH and p-CF3PhOH, imposed significant effects on processing, thermal, and surface properties of corresponding polybenzoxazines. Non-isothermal differential scanning calorimetry (DSC) under diverse heating rates was adopted to investigate the curing kinetics and determine the activation energy of polymerization. DSC results indicate that the m-CF3PhO–/p-CF3PhO– groups have the potential to lower ring-opening polymerization temperature. Glass transition temperatures (Tgs) of polybenzoxazines derived from p-CF3PhOH are higher than that of polymers derived from m-CF3PhOH due to different steric hindrance and crosslinking density. More interesting, all polybenzoxazines show relatively high dielectric constant but exhibit low dielectric loss at ambient temperature.

Keywords

• thermosetting resins
• branched benzoxazine monomer
• phosphazene-core
• low melting point
• high thermal stability