Features of silicon– and titanium–polyethylene glycol precursors in sol–gel synthesis of new hydrogels

Abstract

The formation of organic/inorganic hydrogels based on silicon and titanium polyethylene glycolates, new biocompatible water-soluble precursors in sol–gel processing, was investigated. The influence of different factors on the gelation process, such as excess of PEG, water molar content, pH of medium, electrolyte additives, was investigated in comparison with silicon– and titanium–glycerol precursors. The specific features of gelation for each type of precursor were revealed. It has been determined that titanium polyethylene glycolates synthesized and used in the excess of PEG formed transparent polymeric hydrogels resistant to syneresis under certain conditions. The titanium polyethylene glycolates synthesized without excess of PEG formed turbid heterogeneous colloidal gels. In the case of silicon polyethylene glycolates the hydrogels obtained were polymeric. Dynamic light scattering was used to confirm the polymeric or colloidal type of gelation. The solid and liquid phases of polymeric silicon– and titanium–polyethylene glycol hydrogels were separated by exhaustive extraction. The solid phase was characterized by combined thermal analysis with simultaneous quadruple mass spectrometry, XRD, IR spectroscopy, and liquid phase-atomic emission spectroscopy. The structural features of polymeric gels were investigated by SEM and TEM methods. The cross-linking density of polymeric hydrogels was evaluated using Flory–Rehner theory based on the mechanical properties of swollen networks of flexible polymeric chains.