Accessing Diverse Polymer Architectures through Meldrum’s Acid-Functionalized Polysiloxane Precursors

Meldrum’s acid (MA) is an effective reagent for synthesizing diverse polymer architectures via thermal ketene generation. This study expands MA utilization into hybrid inorganic–organic materials by incorporating it into linear polydimethylsiloxane (PDMS) and cage frameworks from octakis(dimethylsiloxy)silsesquioxane. A series of functionalized copolymers and telechelomers was synthesized via Pt-catalyzed hydrosilylation of allyl-derivatized MA with hydride-terminated PDMS and newly prepared n-octyl-functionalized hydrosilylsilsesquioxanes with 100% atom economy. Upon heating above 275 °C, these precursors underwent decarboxylation to form reactive ketene intermediates, facilitating the formation of cyclobutadione-linked networks, linear polymers, and copolyesters via addition with 4,4’-biphenol. Structural analysis revealed a divergence in reactivity, while PDMS-based telechelomers achieved high conversion (>90%), analogous silsesquioxane-containing systems exhibited restricted chain mobility and significantly lower conversion rates (<20%). However, thermal analysis confirmed that the incorporation of Q8-type silsesquioxane cages enhanced thermal stability (Td up to 425 °C) and high silica char yields (up to 50%). These findings demonstrated MA-functionalized hybrid siloxanes as promising, solvent-processable prepolymer elastomeric coatings for high-temperature applications.