A self-catalytic strategy for ladder-like polysilsesquioxane with multifunctional tertiary amine silane toward high-performance UV/thermal dual-curable coatings

The synthesis of Ladder-like polysilsesquioxane conventionally relies on acidic (HCl) or basic (K₂CO₃) catalysts to promote the hydrolysis–condensation of alkoxysilanes. However, removing these catalysts requires laborious purification procedures, including phase separation, filtration, and solvent evaporation, which complicate the synthesis and cause considerable product loss. Therefore, developing a self-catalytic strategy for preparing Ladder-like polysilsesquioxane remains highly desirable. Herein, we report a facile self-catalytic approach by employing the tertiary amine-functional silane coupling agent 3-( N , N -dimethylamino)propyl trimethoxysilane as an intrinsic catalytic component. The tertiary amine catalyzes alkoxysilane hydrolysis–condensation while serving as an active hydrogen donor during UV-induced free-radical polymerization. This strategy affords Ladder-like polysilsesquioxane (NLLP) with high structural uniformity and a narrow molecular weight distribution. Moreover, the molecular weight of NLLP can be effectively regulated by tuning the reaction time, temperature, and water content. The obtained NLLP exhibits excellent UV-curing performance, achieving a double-bond conversion of approximately 82.9% within 40 s. Notably, 3-( N , N -dimethylamino)propyl trimethoxysilane plays three roles: (i) as a self-catalyst for NLLP synthesis, (ii) as an active hydrogen donor during UV curing, and (iii) as a catalyst for the epoxy–anhydride thermal curing reaction. Based on this multifunctional design, an epoxy-functional MTQ resin was blended with NLLP to construct a UV/thermal dual-curing system, affording an NLLP-MTQ coating with excellent hydrophobicity, high hardness, superior transparency, outstanding flexibility, and UV-aging resistance. This work provides a novel self-catalytic strategy for Ladder-like polysilsesquioxane synthesis and new insights for designing high-performance UV/thermal dual-curable silicone coatings.