Squaramide-directed Cooperative One-dimensional Assembly in Telechelic Polydimethylsiloxane for Hierarchical Network Formation

Abstract

Polymer crosslinked networks often face a fundamental trade-off between the mechanical robustness of covalent systems and the dynamic reversibility of supramolecular assemblies. Inspired by the hierarchical organization of biological extracellular matrix, where fibrous structures are reinforced by covalent crosslinking, we report a squaramide-directed cooperative assembly strategy that integrates one-dimensional (1D) supramolecular nanofiber formation with covalent macromolecular architecture to construct hierarchical polymer networks. Telechelic macromolecules were designed by tethering orthogonally arranged squaramide–amide hydrogen-bonding motifs to polydimethylsiloxane (PDMS) spacers. In the model system, these motifs undergo cooperative nucleation-elongation assembly into long-range nanofibers, while comparison with a urea analogue reveals enhanced intermolecular binding and assembly stability arising from the squaramide motif. Covalent integration of the assembling units transforms discrete nanofibers into microphase-separated networks with increased thermal stability and storage modulus. This work establishes a molecular design principle linking cooperative self-assembly with hierarchical polymer network formation and macroscopic mechanical performance.