Substituent-Dependent Structural Trends in Thermal Condensation of Silanetriols and Disiloxanetetraols.

Oligo- and polysilsesquioxanes are typically synthesized via wet-chemical routes employing acids or bases as catalyst. In this study we report a catalyst- and solvent-free thermal condensation approach for the preparation of oligosilsesquioxanes from arylsilanetriols and their corresponding disiloxanetetraols. Three substituents, namely phenyl (Ph), 1-napthyl (1Np), and 2-naphthyl (2Np) were investigated along with their condensed products. Structural analysis revealed that the Ph and 1Np systems form ladder-like oligosilsesquioxane architectures, whereas the 2Np system exhibits a markedly different structure, suggesting a layered arrangement of planar rings, as supported by FT-IR and PXRD. Comparison of the silanetriols and disiloxantetraols as precursors indicated only minor differences, with crystal structures largely preserved after solid-state condensation reactions. The thermal process achieved a higher degree of condensation than conventional wet-chemical methods and enabled access to structurally distinct products without the need for solvents or catalysts, highlighting its potential for sustainable synthesis of novel polysilsesquioxane materials.