(404e) Expanding the Toolbox of Living Branching Polymerization through Simulation-Informed Reaction Design

Branched polymers exhibit distinct mechanical, photonic, and electrical properties compared to their linear analogs, and have attracted growing attentions in biomedical applications, water treatment, and catalysis. Constructing hierarchically-structured materials integrated with branched functional motifs provides collectively enhanced performance. However, this desirable materials design has been limited by the synthetic difficulty in site-specifically growing polymers with well-controlled degree of branching. In this talk, the presenter will introduce a chain-growth branching polymerization that involves the copolymerization of conventional vinyl monomers with α-haloacrylate comonomers in a copper-mediated atom transfer radical process. The rationally-designed α-haloacrylate will be efficiently converted into branching junctions with the C–halogen bond at the α-position remaining intact until the radical addition occurs. Assisted by the mechanistic studies and kinetic simulations, an optimal profile of the polymerization conditions was obtained. The livingness and degree of polymerization control were both enhanced through an activator regeneration approach combined with a semibatch reactor development. The photo-/electrochemical redox reaction were employed to precisely modulate the activator regeneration rate and suppress the biradical termination reactions. Cross-propagation of comonomers in the copolymerization process was externally regulated by slowing feeding α-haloacrylate at a controlled rate. A diverse variety of vinyl monomers, including acrylates, styrene, acrylonitrile, and acrylamides, were successfully copolymerized with a-haloacrylates to attain high monomer conversion and highly tunable degrees of branching. Hierarchically-branched polymer architectures, e.g., linear-block-branch, branch-on-star, and branch-on-bottlebrush, were prepared through the developed living branching radical copolymerization method.