Quantitative analysis on compressional behavior and swelling kinetics modeling of weakly ionic poly(N,N-dimethylacrylamide-co-acrylic/methacrylic acid or sodium acrylate) gels

A quantitative theoretical description of unusual elastic properties of rubbery materials in terms of the physico-chemical structural parameters remains a challenging task. The equilibrium and dynamic swelling properties of acrylamide-based ionic gels have been analyzed to optimize the design flexibility in terms of the molecular response, the structural integrity, and tunable diffusion behavior. A series of weakly ionic hydrogels and cryogels based on N,N-dimethylacrylamide (DMAAm) and the anionic comonomers acrylic acid (AAc), methacrylic acid (MAAc), and sodium acrylate (NaA) have been prepared by the crosslinking copolymerization using ammonium persulfate as initiator and N,N′-methylenebisacrylamide as crosslinker. By combining the swelling and elasticity data, quantitative agreement was demonstrated and the earlier qualitative observations was confirmed that both the effective charge density distribution and pKa value of weak polyelectrolytes can change substantially the responsive diffusion kinetics depending on the explicit account of charge association/dissociation of incorporated ionic comonomers. The swelling degree of ionic PDMAAm gels can sensitively respond to change in pH of the swelling media and the presence of ionic acrylic segments influences the swelling kinetics of the prepared gels evidently.