Ultrahigh-Molecular-Weight Triblock Copolymers via Inverse Miniemulsion Photoiniferter Polymerization

We report the successful synthesis of ultrahigh-molecular-weight (UHMW, 106–107 g/mol) ABA triblock copolymers through photoiniferter polymerization using solution and inverse miniemulsion conditions. The photoiniferter process was first employed in homogeneous aqueous media to prepare telechelic UHMW poly(N,N-dimethylacrylamide). The effect of the R-group of the iniferter (ZC(═S)SR) on the polymerization control and rate was investigated. The chain-end fidelity of the resulting polymers was verified through sequential chain extensions in solution. Various iniferters were investigated for their hydrolytic stability and partitioning between aqueous and organic phases. Relying on these learnings, the photoiniferter synthesis of UHMW ABA triblock copolymers was achieved under inverse miniemulsion conditions, and the approach was expanded in monomer scope to incorporate 3-acrylamidophenylboronic acid units to impart stimuli-responsive behavior.