Polymerization of Blocked Isocyanate Functional Polymer Surfaces and Post-Polymerization Modification By Thiol-Isocyanate Reactions

Direct polymerization of isocyanate-functional monomers has been achieved with controlled radical polymerizations (CRP) for precisely engineered modification platforms with highly reactive side chains. However, despite the success of these strategies, the inherent reactivity of isocyanates still leads to adverse side reactions, such as hydrolysis, that are difficult to suppress. Phenol, lactam, and oxime-based blocking agents have been used to limit the reactivity of isocyanates in applications such as multicomponent urethane coating systems. The reactivity of these blocked isocyanates can be restored by thermal deprotection of the blocking agent to achieve the desired reactions. In this work, we use blocked isocyanate-functional monomers for surface-initiated polymerization. The isocyanate functional group allows facile modification of the side chains by thiol-isocyanate click reactions, while the blocking agent reduces detrimental side reactions like hydrolysis. We investigate thermally labile blocking agents and report the synthesis and characterization of the blocked isocyanate-functional polymers, followed by deprotection and modification of the isocyanates by reaction with thiols