Hydrazide and blocked isocyanate chemistries are useful for post-polymerization modification (PPM), and have been underutilized for obtaining polymers with controlled architectures. Blocked isocyanates are generated by an equilibrium reaction between isocyanates and, commonly, N-based heterocyles, which can then be reversed thermally or by direct nucleophilic displacement. In this research, we demonstrate the synthesis and use of blocked isocyanate methacrylate-based monomers in RAFT polymerizations to mitigate the sensitivity of isocyanates to water, while maintaining mild, room temperature reactions. By changing the identity of the blocking agent to adjust deblocking conditions, we show that direct nucleophilic displacement of blocking agents occurs readily at room temperature – a result that maintains the salient features of isocyanate reactivity while reducing sensitivity to water.<br/>Hydrazone linkages, a class of dynamic covalent chemistry, are also established through a thermodynamic equilibrium which is controlled by pH. We have investigated the synthesis of hydrazide-containing monomers and the polymerization of these monomers directly by aqueous RAFT polymerization, which, until now, has yet to be achieved. Direct polymerization of hydrazide monomers opens doors to libraries of polymers that can shuffle or exchange pendent groups thereby enabling the design of new dynamic combinatorial polymer libraries for a wide range of applications. The dynamic nature of both the blocked isocyanates and hydrazone functional polymers promotes facile and versatile post-polymerization modification.

Facile post-polymerization modification of blocked isocyanate and hydrazide containing polymers

249th National Meeting (2015)

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