Intermolecular crosslinking of poly(acrylic acid) in aqueous solution by electron beam irradiation

Poly(acrylic acid) (PAA) was dissolved in water, and the solution was irradiated with high-energy electrons. The formation of macroscopic gel was studied as a function of the radiation dose, the pH of the aqueous solution, and the concentration of added salt. Gelation by intermolecular crosslinking was found at low pH values of 2–4, whereas at pH greater or equal to 5, no gel was formed by electron beam irradiation. Nevertheless, by adding monovalent salt the gel formation was enhanced at intermediate pH values. The intermolecular crosslinking was assumed to be inhibited by electrostatic repulsive forces when the macromolecules of PAA are negatively charged and the ionic strength of the solution is low. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010