Temperature- and pH-sensitive hydrogels of sequential Ti-containing interpenetrating polymer networks

Abstract

Hydrogels of sequential Ti-containing interpenetrating polymer networks based on hydrophilic cross-linked polyurethanes with different molecular weight of polyethylene glycols and Ti-containing copolymer were synthesized based on 2-hydroxyethyl methacrylate and titanium isopropoxide. The composition of sequential interpenetrating polymer networks was determined by the degree of equilibrium swelling of the polyurethane networks in 2-hydroxyethyl methacrylate and Ti-containing comonomer. It was established that the content of the second component of the interpenetrating polymer networks increases with increasing the average molecular weight value of the polyurethane network. It was shown that the obtained highly sensitive hydrogels of Ti-containing interpenetrating polymer networks react to the changes in the temperature and pH. These factors significantly change the equilibrium water content in the hydrogels. Differential scanning calorimetry allowed determining the phase transitions that are characteristic of bound and free water, which is a part of the hydrogel of polyurethanes, interpenetrating polymer networks and Ti-containing interpenetrating polymer networks. The results showed that the content of bound water and the degree of its binding to the components of the interpenetrating polymer networks depend on the chemical structure of the network, the nature of a second polymer component (which is a part of the interpenetrating polymer networks), the polarity and hydrophilicity of macromolecules, and the size of hydrogel cells. Regardless of the nature of the second polymer component, there is a general trend for all interpenetrating polymer networks: the total water content increases with increasing the average molecular weight of the polyurethane matrix networks.