# Programmable Stereoregular Fully Aromatic-Substituted Polymethylenes

## TL;DR

Scientists created a new type of polymer with fully aromatic substitutions and programmable structure, enabling new functional materials.

## Contribution

A new class of polymers with fully aromatic substitution and programmable tacticity is synthesized via controlled C1 polymerization.

## Key findings

- Two catalytic pathways enabled stereoregular poly(phenylmethylene)s with controlled molecular weights.
- The polymers exhibit unique thermal, photochemical, and supramolecular properties.
- This work introduces a new structural framework for carbon-chain polymers beyond conventional polyolefins.

## Abstract

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.