The effect of crosslinker concentration on swelling behavior of pH-responsive IPN hydrogels based on poly(hydroxymethyl acrylamide)

Homopolymer hydrogel polyacrylamide and poly (N-methylol acrylamide) also Interpenetrating Polymer Network (IPN) hydrogel polyacrylamide–poly (N-methylol acrylamide) were synthesized using free radical polymerization. Various concentrations of N, N’- methylene bis acrylamide (MBA) as crosslinkers were used to determine their effect on swelling in various pH. Variation of crosslinker concentrations caused changes in the hydrogel structures and thus affected the swelling ratio. The polymerizations were conducted successfully, which was proven by the loss of the C=C and C-H sp2 alkene peaks on FTIR spectra. Morphology characterization with SEM was observed on IPN PNMA hydrogel and it was found that it had pore size in the range of 400–700 nm. Swelling test was carried out at room temperature and pH 3, 5, 7, 9, and 12. Swelling ratios of IPN hydrogels were found to be higher than homopolymer hydrogel because the presence of the second network. The highest swelling ratio in different pH for PNMA and IPN hydrogels was found at pH 5.