New stimuli-responsive copolymers of N-acryloyl-N '-alkyl piperazine and methyl methacrylate and their hydrogels

Water-soluble copolymers of N-acryloyl-N'-alkylpiperazine (alkyl: methyl, e thyl) with methyl methacrylate were synthesized and the lower critical solu tion temperatures (LCSTs) of the copolymers which depend on the composition s and pH of the aqueous solutions are described. The effects of cationic su rfactants and simple inorganic salts on the LCSTs are also reported. The in fluences of pH and temperature on the swelling of the ionizable and thermos ensitive hydrogels are studied. (C) 2000 Elsevier Science Ltd. All rights r eserved.