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45286-G7
Reversible Self-Assembly of Boronic Acid-Containing Block Copolymers
Organoboron polymers are important precursors to materials with potential utility in catalysis, separations, and sensing applications and offer promise as electrolyte materials for batteries, blue emissive polymers, self-healing materials, precursors for functional polyolefins, and as potential surfactants for enhanced oil recovery. In order to more fully realize the potential of boronic acid-containing macromolecules in these fields, it is vital to expand the capability to prepare such polymers with precise control over topology, molecular weight, and composition. Our research is focused on devising methods for the synthesis of well-defined, water-soluble boronic acid copolymers from stable and easily manipulated boron-containing monomers. Additionally, we have employed highly efficient “click” chemistry techniques to further incorporate boron-containing moieties by postpolymerization modification.
During the past year, we have successfully established a facile route to well-defined boronic acid (co)polymers from stable and easily manipulated boronic ester monomers. The polymerization of 4-pinacolatoborylstyrene by reversible addition-fragmentation chain transfer (RAFT) yielded polymeric boronic acid precursors, and appropriate selection of stoichiometry allowed tuning of polymerization kinetics and targeting specific molecular weights in the range of Mn = 17,000 – 32,000 g/mol. The resulting low polydispersity poly(4-pinacolatoborylstyrene) homopolymers were employed as macro chain transfer agents for block copolymerization with N,N-dimethylacrylamide to yield amphiphilic block copolymers that formed micelles in aqueous media. The pinacol ester derivatized (co)polymers were easily deprotected by a mild and convenient strategy to yield free boronic acid polymers.
Current and future research will build on our success in preparing boronic acid derivatives of functional precursor polymers by postpolymerization modification via copper-catalyzed azide-alkyne click chemistry. Over the course of this project, we have successfully employed click functionalization to prepare macromonomers, azide functional RAFT chain transfer agents, and hyperbranched polymers with specific solubility response. 
