Thermo-sensitive hydrogel derived from vinylbenzyltributylphosphonium chloride

Vinlbenzyltributylphosphonium chloride (VBTBPCl) affords a cloud point in a queous solutions, depending on its concentration and the concentration of s odium chloride added. VBTBPCl was polymerized under several conditions. The linear polymers derived from VBTBPCl also gave lower consolute temperature s. The VBTBPCl polymers cross-linked by divinylbenzene were significantly s wollen in the low NaCl aqueous solutions at low temperatures. The hydrogel suddenly shrank at a certain temperature, indicating a volume-phase-transit ion. The temperature was closely related to the phase-separation temperatur e of the linear polymer. The relationship between NaCl concentration and vo lume-phase-transition temperature was studied in detail.