Chapter 9 - Light-Induced Reactions of Benzoxazines and Derivatives

Abstract

This chapter describes photochemical routes for the incorporation of thermally polymerizable benzoxazine in linear and cross-linked polymeric structures. It focuses on the use of both the free radical and cationic photoinitiating systems for benzoxazine resins that provide some advantages or overcome existing problems and challenges in benzoxazine chemistry. The photochemical degradation and UV stability of benzoxazine resins are also discussed in this study. Benzoxazine resins are readily synthesized from benzoxazine monomers, either monofunctional or of higher functionality. It elaborates that photoinitiated polymerization is an important industrial process widely used in different applications. This process induces the polymer formation with a fast transformation of the liquid monomer into a solid film with tailored physical chemical and mechanical properties. This is a striking advantage for both the classical polymerization of monofunctional monomers and modern curing applications. Photopolymerizations are simply polymerization reactions initiated by light, typically in the ultraviolet or visible region of the light spectrum. Photoinitiated polymerization can be divided into two categories: free radical and cationic polymerizations. Deep curing using the described photoinitiating system followed by the thermal ring-opening of the incorporated benzoxazine groups provides highly dense cross-linked networks. The thermal cross-linking nature may be used to prepare high-performance thermoset polymers with diverse properties featuring self-supporting and flexible films. The hydrophilicity and wettability of benzoxazine films can also be changed by light. Such material is well-suited for applications such as coating and microelectronics where film formation is needed.