Effects of Soft Confinement of a Bottlebrush Polymer Reactor on the Polymerization Reaction

Molecular reactors offer molecular-level spatial confinement that enables precise control of reactions. Recently, we developed a bottlebrush polymer reactor (BBPR), a versatile molecular reactor based on bottlebrush polymers that can host various polymerization reactions, including Suzuki−Miyaura cross-coupling (SMC) polymerization. Yet, how the nanoscale soft confinement of a BBPR influences on polymerization reaction has remained elusive. Herein, we employ polythiophene as a molecular probe to investigate the effects of confinement provided by BBPRs. SMC polymerization in BBPR bearing thiophene monomers attached to the backbone produced oligomeric polythiophene chains. The sterically crowded environment inside the BBPRs shifted the competitive balance of the SMC reaction and a homocoupling side reaction, leading to altered regularity of the resulting chain. The monomer loading was found to effectively control the molecular weight of the product polythiophene. For the first time, the unique nanoscale crowded environment inside a BBPR was shown to directly modulate the polymerization pathway and structural order of conjugated polymers, underscoring their potential as a novel tool for tailoring polymerization reactions.