Collapse of hydrogels based on copolymers of N-isopropylacrylamide and sodium vinylsulfonate

This paper describes the investigation of the behavior of polyelectrolyte thermosensitive hydrogels based on copolymers of N-isopropylacrylamide and sodium vinylsulfonate at different temperatures. The influence of ionogenic groups on the swollen gel-collapsed gel phase transition was studied by means of highly sensitive differential scanning calorimetry. It was demonstrated that the presence of ionogenic groups in the thermosensitive copolymer influences the reversibility and the amplitude of gel collapse, as well as the temperature, enthalpy, and increment of the transition heat capacity.