Catalytically Active Polyols for Fast-Curing Aliphatic Polyurethane Coatings with On-Demand Debonding

Abstract

Thermosetting aliphatic polyurethanes are highly attractive for transparent coating applications owing to their excellent optical clarity and superior UV resistance; however, their intrinsically low reactivity generally requires prolonged curing times or the use of external catalysts. Herein, a series of self-catalytic liquid polyols were developed through solvent-free aza-Michael reactions between the multifunctional Michael acceptor 1,3,5-triacryloylhexahydro-1,3,5-triazine (TAHT) and secondary aminoalcohols, simultaneously generating tertiary amine-containing polyol structures capable of intrinsically catalyzing urethane formation. The resulting polyols enabled fast catalyst-free curing of hexamethylene diisocyanate isocyanurate trimer (HDI trimer)-based aliphatic polyurethane thermosets under mild conditions, exhibiting dramatically accelerated curing behavior compared with conventional non-catalytic systems. The obtained transparent thermoset showed excellent optical clarity together with robust thermomechanical and coating performance. Furthermore, efficient debonding-on-demand behavior was achieved using citric acid-catalyzed hydrolysis, enabling complete coating debonding and substrate recovery without damaging the underlying aluminum substrate. These findings demonstrate a versatile molecular design strategy for aliphatic polyurethane coating systems that are rapidly curable without external catalysts, transparent, and selectively removable on demand.