A novel bio-based polybenzoxazine prepared from fluorinated Schiff base and furfurylamine with superior thermal, flame-retardant and superhigh-frequency low dielectric properties

Abstract

In pursuit of high-performance and environmentally friendly materials for superhigh-frequency communication applications, a novel biobased benzoxazine resin (poly(SF-f)) is firstly synthesized from fluorinated Schiff base based bisphenol (SF) and furfurylamine. The bulky fluorinated Schiff base structure in SF can impart low polarity, enhance flame retardancy, and reduce the density of polar group, while low polar and reactive furan ring in furfurylamine can increase the cross-linking density. Interestingly, the newly developed benzoxazine SF-f exhibits the lowest onset polymerization temperature, relatively high exothermic enthalpy, and relatively low activation energy compared to other similar structures, due to the presence of both Schiff base moiety and furan ring. Notably, the prepared benzoxazine resin displays good thermal and flame retardancy properties, including the glass transition temperature of 302 °C, the char yield at 800 °C of 56.5%, the limiting oxygen index of 40.10, the heat release capacity of 30.9 J/g K, the total heat release of 2.9 KJ/g, and UL-94 V-0 rating. Besides, the poly(SF-f) also shows low dielectric constants (2.73, 5 GHz; 2.68, 10 GHz) and low dielectric losses (0.0064, 5 GHz; 0.0062, 10 GHz), resulting from the increased cross-linking density, strengthened hydrogen-bonding, and decreased molecular polarity. Therefore, this study not only provides an effective method to design and prepare bio-benzoxazine resin containing Schiff base with good comprehensive properties of high thermally stable, intrinsic flame-retardant, and superhigh-frequency low dielectric properties, but also gives a new insight for the development of high-performance benzoxazine chemistry.