HYDROGELS FROM ACRYLIC ACID WITH N,N-DIMETHYLACRYLAMIDE: SYNTHESIS, CHARACTERIZATION, AND WATER ABSORPTION PROPERTIES

Copolymer hydrogels of acrylic acid (AA) with N,N-dimethylacrylamide (NNDMAAm) were synthesized by solution free radical polymerization at different feed mol monomer ratios. The monomer reactivity ratios were determined by Kelen-Tüdös method. According to that, the monomer reactivity ratios for poly(AA-co-NNDMAAm) were r1 = 0.650 (M1=AA) and r2= 1.160 (M2=NNDMAAm), (r1 x r2= 0.753). The effect of reaction parameters including: the concentration of cross-linking reagent, monomer concentration, pH, temperature, salt solutions, and solvent polarity on the water absorption have been studied. The hydrogels achieved water-absorption values of 544 g water/ g xerogel for the copolymer poly(AA-co-NNDMAAm) 3:1 atpH 5. Low critieal solution temperature (LCST) values of hydrogels, showed an increase whenthe hydrophilic AA moiety eontent increased in the copolymers.