Malonic Ester Synthesis-Type Polymerization: Synthetic Platform for Systematic Control of Constitutional Repeating Units in sp3 Carbon-Chain Polymers

Abstract In sp3 carbon-chain polymers, side-chain functionality can be readily diversified, whereas systematic control over side-chain spacing within the constitutional repeating unit (CRU) remains largely unexplored. Here, we report malonic ester synthesis–type polymerization (MESP), an A2 + B2 polycondensation that exploits nucleophilic substitution between malonate enolates and alkyl bromides to access sp3 carbon-chain polymers with single-carbon differences in side-chain spacing. Post-polymerization decarboxylation converts gem-bis esters into monoester side chains, yielding acrylate–ethylene copolymer analogues with controlled composition and sequence. Thermal analysis reveals polymer properties spanning amorphous to semicrystalline regimes, with odd–even effects arising from single-carbon variations in gem-bis ester placement relative to the methylene spacer. By unifying backbone and side-chain design within a single strategy traditionally associated with polyesters and polyacrylates, respectively, MESP expands the accessible CRU landscape and provides a platform for the discovery of new functional carbon-chain polymers through precise control of functional group arrangement and spacing within their CRU.