Methacrylate and Styrene Block Copolymer Synthesis by Cu-Mediated Chain Extension of Acrylate Macroinitiator in a Semibatch Reactor

A process for the well-controlled growth of acrylates by Cu-mediated polymerization has been developed, with macroinitiator synthesized continuously in a copper tubular reactor and subsequently chain-extended in a semibatch reactor without additional copper. Extending this process to methacrylates and styrene, however, has proven difficult due to a significant reduction in reaction rate. This barrier has been overcome by chain-extending the low molecular weight (M-n of 760 g mol(-1)) poly(methyl acrylate) macroinitiator with methacrylates and styrene using PMDETA (N,N,N ',N '',N ''-pentamethyldiethylenetriamine) as ligand. Methyl methacrylate conversions of >80% at 70 degrees C and diethylene glycol methyl ether methacrylate conversions of >90% at room temperature are achieved in 4 h, with the same room temperature conditions successfully applied for controlled chain extensions with butyl methacrylate. Although styrene conversions are slightly lower (60-70%) over 4 h at 85 degrees C, the rates achieved are substantially higher than achieved in other studies. Hydrophobic-hydrophilic triblock structures are produced through sequential monomer feeds to the semibatch reactor, keeping total reaction time to less than 5 h. The ability to incorporate methacrylates and/or styrene into structured block polymers greatly extends the range of products that can be efficiently synthesized with low copper levels by this process.