CHEMICAL CONDITION RESPONSIBLE FOR THERMOSWELLING OF THERMOSHRINKING TYPE OF VOLUME PHASE-TRANSITION IN GELS - EFFECT OF RELATIVE AMOUNTS OF HYDROPHOBIC TO HYDROPHILIC GROUPS IN THE SIDE-CHAIN

Thermoreversible volume phase transitions were observed for three polyacrylamide derivative gels, acrylamide (Am)-sodium acrylate (SAc)-NN'-methylenebis(acrylamide) (Bis) copolymer gel (SAc gel), Am-sodium vinylacetate (SVA)-Bis copolymer gel (SVA gel), and Am-sodium allylacetate (SAA)-Bis copolymer gel (SAA gel). SAc and SVA gels underwent thermoswelling volume changes, and SAA gel, thermoshrinking volume change. The chemical conditions that cause a gel to thermoswell or thermoshrink can be clearly determined from the relative molar ratio of a hydrophobic group to the hydrophilic group in the gel. The transition,from thermoswelling to thermoshrinking occurs with a change in the relative molar ratio from 1 to 2.