Hydrogels prepared by crosslinking copolymerization of N-allyl maleamic acid with acrylamide and acrylic acid

Copolymerization of N-allyl maleamic acid (AMA) with acrylamide and acrylic acid results in rapid crosslinking in water. Although AMA is slightly soluble in water, it forms clear solutions in 10% of aqueous acrylamide and 20% acrylic acid solutions. By radical initiation with potassium persulfate at 65°C or redox initiation at 0°C, these solutions undergo gelation in less than 10 min. The crosslinking efficiency of AMA was estimated based on equilibrium swellings of its acrylamide copolymer gels either by the Flory-Rehner theory or by correlation with swelling-crosslinking density plots of acrylamide-methylene bis-acrylamide (BIS) copolymer gels. These results showed that efficiency of AMA in crosslinking copolymerization with acrylamide at 0°C is less than 10%. On the other hand, its efficiency rises up to 40-60% and levels off at 65°C. Overall results indicate that AMA having maleate and allylic double bonds is an efficient crosslinker for preparing polyacrylamide and polyacrylic acid gels.