pH and temperature responsive hydrogels of poly(2-acrylamido-2-methyl-1-propanesulfonic acid-co-methacrylic acid): Synthesis and swelling characteristics

Temperature and pH sensitive 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and methacrylic acid (MAA) homopolymer and copolymer hydrogels have been prepared using N,N-methylenebisacrylamide (MBA) and ethylene glycol dimethacrylate (EGDMA) as crosslinkers. Swelling of these hydrogels has been studied in terms of monomer ratio, type and concentration of the crosslinkers and in various concentrations of mono, di and trivalent salt solutions. Though swelling of the EGDMA crosslinked poly(AMPS-co-MAA) hydrogels is found to be higher than those based on MBA crosslinker, strength of the latter system has been found to be better. Swelling behavior of these hydrogels in different salt solutions at different concentrations has shown a drop in swelling from monovalent to trivalent cations and also at higher salt concentrations. The results have indicated the possibilities of developing tailor made hydrogels combining optimum swelling with better strength characteristics that will suit different physiological and biological environments.