Hydroxyl Terminated Hydrophilic Silanes

Abstract

Hydroxyakyl terminated silanes were prepared by reacting 3-aminopropyl alkoxysilanes with ethylene carbonate. Unlike most silanes, these hydrophilic silanes are partially hydrolyzed in water and the siloxane oligomers thus obtained remain soluble in the water. Further condensation leads to water soluble linear or branched polysiloxanes depending on the structure of the hydroxylalkyl terminated silane. The water solubility is not limited to a narrow pH range and does not require alcohols (or other additives). The preparation method of these silanes was found to proceed smoothly at RT with no need for a solvent or a catalyst. The reactions followed second order reaction kinetics irrespective of the number of alkoxy groups attached to the silicon atom. Some condensation was unavoidable even in the absence of any catalyst but the viscosity remained low (0.10–0.16 Pa·sec) and was primarily dependent on the density of branching and the extent of the hydrogen bonding. The structures of these silanes were confirmed by FTIR, 1H NMR and 29Si NMR.