Correlation between molecular structures and reaction conditions (temperature–pressure–time) in the preparation of secondary, tertiary, and quaternary ammonium-functionalized polyhedral oligomeric silsesquioxanes

Polyhedral oligomeric silsesquioxanes (POSSs) were prepared by the hydrolytic condensation reaction of organotrialkoxysilanes containing secondary and tertiary amino moieties, as well as quaternary ammonium groups. The employed methodology involved using aqueous trifluoromethanesulfonic acid (HOTf) as the catalyst and solvent at various temperatures and pressures in a Kugelrohr apparatus, which controlled the solvent evaporation time. At lower setting temperature (60 °C) or at shorter solvent evaporation times (≤2 h), the main product was a cage octamer (T8-POSS). Moreover, even at higher temperatures (≥100 °C), the T8 compound was the primary product observed for short evaporation time (≤1.5 h). However, when the solvent evaporation times increased (≥4 h, controlled by pressure) at higher temperatures (≥100 °C), the proportion of a cage decamer (T10-POSS) in the POSS mixtures was larger. Hence, T10-POSS was formed more readily than the corresponding T8 compound when the solvent was evaporated at higher temperatures and over the longer periods of time.