Nanostructured Hybrid Binders: Enhancing HTPB–Polyurethane Elastomers Through Precise Q-Siloxane Grafting

Abstract

The strategic synthesis of polyhedral oligomeric silsesquioxane (POSS) functionalized hydroxyl-terminated polybutadiene (gHTPB) and its integration into segmented polyurethane (PU) elastomers is reported. A two-step platinum-catalyzed hydrosilylation protocol was developed, utilizing precise equivalents of 1-octene to partially functionalize octakis(dimethylsiloxy)silsesquioxane (Q₈M₈ ^H) and isolate the mono-functional intermediate Q₈M₇ ^OM₁ ^H. This intermediate was subsequently grafted onto the vinyl pendants of an HTPB backbone, facilitating the high-fidelity incorporation of the inorganic POSS cages while maintaining terminal hydroxyl functionality. Subsequent curing with isophorone diisocyanate (IPDI) yielded a series of nanostructured PU hybrid copolymers and terpolymers. This methodology provides a robust route for tailoring the inorganic content and architecture of liquid rubber pre-polymers, offering a versatile platform for the development of high-performance elastomeric binders with enhanced thermal and rheological properties.