Self-Stratifying Supramolecular PDMS Adhesives with Strong Interfacial Bonding, Room-Temperature Self-Healing, and Recyclability

Polydimethylsiloxane (PDMS) materials are widely used due to their flexibility and low surface energy, yet their inherently weak substrate adhesion, lack of intrinsic room-temperature self-healing, and poor recyclability severely restrict high-value and sustainable applications. Herein, we report a supramolecular PDMS-based system that simultaneously achieves strong interfacial adhesion, rapid room-temperature self-healing, and efficient recyclability through rational molecular design. By grafting 2-ureido-4[1H]-pyrimidinone (UPy) motifs onto a thiol-containing polyester–PDMS backbone via thiol–ene chemistry, a dynamically cross-linked network featuring reversible quadruple hydrogen bonding was constructed. The UPy units serve dual roles: at moderate loading, they form reversible physical cross-links that enable fast intrinsic self-healing at room temperature; above a critical threshold, they self-assemble into microcrystalline domains that significantly enhance mechanical strength and storage modulus. Meanwhile, polarity contrast between siloxane chains and UPy moieties induces an intrinsic self-stratifying effect, where low-surface-energy PDMS segments enrich at the air interface while polar UPy groups accumulate at the substrate interface. This spatial organization reconciles the long-standing conflict between surface hydrophobicity and strong adhesion, leading to lap shear strengths exceeding 1 MPa on diverse substrates without complex pretreatment. Importantly, the fully supramolecular network allows repeated recycling via solvent treatment or hot pressing with negligible performance degradation. This work establishes a unified strategy that integrates dynamic hydrogen-bond cross-linking and interfacial self-organization, offering a promising molecular design strategy for repairable, recyclable, and high-performance silicone adhesives and coatings.