Controlled Dual Cross-Linking of Radical and Urethane Reactions via Vinyl Protection for High-Performance Coating Materials

Herein, we present a method to control the dual cross-linkingofradical and urethane reactions for the enhanced polymer coatings byprotecting and deprotecting vinyl functionalities using sulfoxidechemistry. We exploited this chemistry to produce highly cross-linkedpolymers suitable for use as protective coatings. Briefly, duallycross-linkable polymers with sulfoxide-protected vinyl and hydroxylfunctionalities were synthesized. Subsequently, thermal curing resultedin the reaction of the hydroxyl functionalities with isocyanate cross-linkersto form urethane cross-links. At the same time, the sulfoxide-protectedvinyl functionalities were deprotected and participated in vinyl cross-linkingvia radical addition reactions. The real-time monitoring of the dual-cross-linkingbehavior and mechanical properties of the cross-linked films revealedenhanced cross-linking when the reaction rate of the vinyl functionalitieswas retarded during thermal curing. Thus, this work provides insightsinto methods of enhancing dual-cross-linking reaction efficiency,and the developed system has applications for the low-temperaturepreparation of automotive clearcoats.