A new hydrogel system undergoing a volume phase transition upon heating

摘要

A new hydrogel system capable of a thermotropic collapse at about 47deg C is the complex poly(diallyldimethylammonium chloride)/sodium dodecyl sulfate (PDADMA-C1/SDS). It was found that the stoichiometric complex of PDADMA-C1/SDS being highly ordered in the collapsed state is capable of swelling strongly in the presence of excess SDS. Upon swelling the gel loses its ordered structure and becomes transparent. The hydrogel shrinks upon heating approaching its initial volume. However, in the newly achieved collapsed state the gel has no ordered structure and the volume phase transition is associated with drastic changes in the heat capacity typical of co-operative conformational and phase transitions. It is reasonable to suggest that this hydrogel system is only an example of a wide group of thermosensitive polymer systems which may undergo conformational and phase transitions.