Dynamically Tuning the Kuhn Length to Expand Property Control of Polymer Networks.

The flexibility of a polymer chain governs molecular packing and viscoelastic properties of melts, elastomers, and gels. In synthetic systems, chain rigidity is typically increased by modifying chemical structure through the addition of bulky pendant groups, ionic moieties, aromatic rings, and helical motifs. However, these approaches offer limited tunability of persistence length and are synthetically restrictive. In bottlebrush systems, backbone flexibility is conventionally tuned via side-chain length and grafting density, but because persistence length scales with brush diameter (l_p∝d), molecular packing and material properties remain intrinsically coupled. We address this limitation by introducing controlled hydrogen bonding along the brush backbone to modulate persistence length while preserving overall chemical composition. By adjusting hydrogen bond concentration, we shift the relaxation time and reshape the viscoelastic profile. Given the dynamic nature of hydrogen bonding, these networks exhibit unique order-disorder and viscous-elastic transitions in response to temperature and strain rate, ultimately creating customizable materials to address unmet needs in soft matter engineering.