Programmable Stereoregular Fully Aromatic-Substituted Polymethylenes

The discovery of new classes of polymers continues to redefine the scope of macromolecular chemistry. However, one category has remained largely unexplored: fully aromatic-substituted polymethylenes bearing functional groups on every backbone carbon. These polymers represent the densest functionalization achievable in carbon-carbon chain backbones but have long been regarded as synthetically inaccessible because of severe steric congestion. Furthermore, achieving stereoregularity in C1 polymerization remains challenging, as the mechanism involves an additional elimination step and is highly sensitive to steric and electronic effects. Here, we report a controlled C1 polymerization that enables the synthesis of stereoregular and functionalized poly(phenylmethylene)s, a fundamentally new class of carbon-chain polymers that combine fully aromatic backbone substitution with programmable tacticity. Two distinct catalytic pathways were developed: (1) a carbenium-initiated cationic polymerization affording isotactic polymers, and (2) a Ni(acac)₂-induced carbene polymerization affording syndiotactic polymers. Both methods produce polymers with controlled molecular weights, diverse aryl substituents, and distinct thermal, photochemical, and supramolecular characteristics. This work establishes a new structural structural framework for carbon-chain polymers that integrates functionality and stereoregularity, thus opening new avenues for designing functional materials beyond the limits of conventional polyolefin chemistry.