ABSTRACT
The study of stimule-sensitive and responsive hydrogels has been one of the most exciting research areas for polymer scientists. The effects of various kinds of stimulation such as temperature change, pH change, pressure change, photoirradiation, ultrasound irradiation, and introduction of electrical field and magnetic field on the stimule-sensitive hydrogels have been studied. This chapter describes some synthetic polyelectrolyte gels and polysaccharide-polyacrylate composite gels, and discusses mainly in relation to the electrosensitive and responsive properties of stimule-sensitive hydrogels. The principle of stimule sensitivity in hydrogels varies with the kind of stimulation. Though stimule sensitivity differs with the kind of stimulation, it is possible to relate the different kinds of sensitivities to each other. In general, a hydrogel is synthesized by any kind of gelation technique, such as ionic reaction, polymerization, polycondensation, polyaddition, or cross-linking. Synthetic polymers are usually prepared by polymerization and cross-linking in the presence of suitable cross-linkers.
