Systematic Design and Synthesis of Methacrylate- and Trimethoxysilane-Functionalized POSS and DDSQ Nanostructures

Polyhedral oligomeric silsesquioxane (POSS) and double-decker silsesquioxane (DDSQ) are organic–inorganic hybrid nanostructures with well-defined siloxane frameworks that can be functionalized with various organic groups. In this study, a systematic series of six functional silsesquioxane derivatives was prepared using three different molecular architectures, POSS-8, DDSQ-4, and DDSQ-2. Three methacrylate-functionalized derivatives and three trimethoxysilane-functionalized derivatives were prepared from the corresponding Si–H-containing POSS and DDSQ precursors through hydrosilylation reactions. The target compounds were obtained in good yields of 81–91%, and their molecular structures were characterized by FT-IR, 1H and 13C NMR, 29Si NMR, and MALDI-TOF mass spectrometry. The spectroscopic results confirmed the successful introduction of the methacrylate and trimethoxysilane groups while maintaining the characteristic silsesquioxane frameworks. The parallel functionalization of POSS-8, DDSQ-4, and DDSQ-2 established a systematic series of silsesquioxane molecular precursors differing in framework architecture and peripheral functional-group density. The resulting derivatives contain either methacrylate or trimethoxysilane functionalities; however, their subsequent polymerization, hydrolysis/condensation, and material performance were not evaluated in the present study. Accordingly, these compounds are regarded as potential molecular precursors for further investigation.