Twisted-Amide Design Enables Access to Functional Methacrylate–Styrene Alternating Copolymers through Postpolymerization Modification

Abstract

Sequence-controlled vinyl polymers provide unique opportunities to investigate how monomer sequence influences material properties; however, access to structurally diverse alternating copolymers remains challenging. Here, we report a molecular design strategy that introduces a twisted-amide structure into side-chain transformable methacrylamide to enhance postpolymerization alcoholysis transformability. Density functional theory (DFT) calculations revealed that the amide moiety adopts a highly twisted conformation, which facilitates nucleophilic substitution by alcohols. This design enables efficient postpolymerization transformation to yield a series of methacrylate–styrene alternating copolymers bearing diverse side chains, including bulky and fluorinated substituents. The resulting copolymers exhibit distinct sequence-dependent properties. In particular, sequence-specific thermal properties were observed, with alternating copolymers exhibiting substantially lower glass transition temperatures than the corresponding statistical copolymers and pronounced negative deviations from the Fox prediction, indicating a pronounced sequence effect arising from the disruption of consecutive bulky units. Furthermore, sequence-defined block copolymers composed of two alternating segments were successfully synthesized and found to exhibit microphase separation behavior driven by segmental incompatibility. These results demonstrate that the twisted-amide design provides a versatile platform for postpolymerization modification and enables access to sequence-controlled architectures with tunable thermal and phase behavior.