A
polymer gel is a cross-linked three dimentional polymer networks that
contains liquids in its internal space. It is a soft matter
intermediate between a solid and a liquid. The gel shows discontinuous
volume change when a external stimuli such as temperature, light and
electric field, is imposed upon it. It is called a stimuli
responsiveness.
The polymer gel swells or shrinks when
external condition such as ion strength or solvent composition is
changed. It is called a phase transition. The phase transition in gels
caused by four fundamental interactions, i.e. hydrogen bonding,
hydrophobic interaction, van der Waals interaction and ionic
interaction between ionized groups.
There are many potential applications of the polymer
gels such as the separation of solutes or metal ions,
immobilization of enzymes and drug delivery system. New application
also has been developed, in which gel networks are used as a reaction,
separation and/or chemo-mechanical energy transformation media, for
example, adsorbents, membranes, chromatography and preparation of fine
particles in the gel networks.