Supramolecular Polymer Materials Assembled via Polymerization and Subsequent Cross-Linking through a Single Hydrogen-Bonding Motif

Supramolecular polymers offer reversible and sustainable properties but are limited by weak mechanical strength and complex motifs. Cross-linking enhances robustness, although examples that employ the same interaction for both polymerization and cross-linking remain rare. In this study, linear supramolecular polymerization and subsequent cross-linking are achieved using the same hydrogen-bonded functional groups through a relatively simple synthetic route and intermediates. The key concept is that the vertical hydrogen bonding of urea groups is kinetically inhibited by the sterically hindered bulky double-decker-shaped phenyl-substituted silsesquioxane (DDSQ) framework. DDSQ-based bisurea is prepared by the hydrosilylation of 1-allyl-3-hexylurea with bisdimethylsiloxy-functionalized DDSQ. The solution viscosity of DDSQ bisurea indicates that the supramolecular polymer chain exhibits Zimm-like behavior. Increasing the concentration and viscosity of the DDSQ bisurea leads to a semidilute entangled regime and sticky Rouse model. Dissolving DDSQ bisurea in chloroform and casting onto a glass plate yielded a transparent, flexible film. Upon annealing at 70 °C for 12 h, the transparent film becomes turbid owing to cold crystallization, and its thermal conductivity increases from 0.19 to 0.39 W m –1 K –1 . Overall, this study establishes a simple strategy for producing robust, flexible, and thermally responsive supramolecular polymers using a single hydrogen-bonding motif, providing a practical pathway toward sustainable, high-performance materials.