Dynamic covalent linkages are stable bonds formed as a result of an equilibrium established between starting material and product that can be reversed under a specific set of conditions. Hydrazone bonds make up an important class of dynamic covalent linkages useful for applications ranging from self-healable materials to attachment and release of molecules of interest for therapeutics. Installing dynamic covalent linkages on polymers has become has, therefore, become a rapidly growing area of research due to its potential impact on a wide range of applications.Herein, we report the synthesis of monomers for direct and indirect polymerization of hydrazide functional groups by reversible addition-fragmentation chain transfer (RAFT) polymerization in order to synthesize hydrazone functional polymers. A couple of examples of hydrazide functional polymers by post-polymerization modification have been reported, however, direct polymerization of a hydrazide moiety has, until recently, yet to be achieved. We investigated the polymerization of N-methacryloyl hydrazide directly by aqueous RAFT at various pH's and the polymerization of N-methacryloyl carbazate by RAFT in organic media as an indirect route to achieve hydrazide functional polymers. The synthesis of hydrazide polymers by controlled radical polymerization opens the door to new types of dynamic covalent polymer architectures in solution. The dynamic nature of these hydrazone linkages enables the functionalized polymers to shuffle or exchange pendent groups providing a versatile polymer scaffold for development of dynamic combinatorial polymer libraries. Different monomer structures were also designed to determine its influence on hydrazone formation and exchange after polymerization.

Direct and indirect synthesis of hydrazide containing polymers via RAFT

248th National Meeting (2014)

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