Unusual behaviour of crosslinked and linear forms of a zwitterionic polymer in aqueous alkali

Novel findings are reported on hydrogels and aqueous solutions of the zwitt erionic polymer, poly[1-(3-sulfopropyl)-2-vinylpyridinium-betaine]. In aque ous media of high pH: (a) the chemically crosslinked polymer develops a red dish-brown coloration followed by physical disintegration and dissolution, and (b) the corresponding linear polymer exhibits the same coloration and u ndergoes a reduction in molecular weight, solution viscosity and T-g. These finding lie in sharp contrast to normal behaviour exhibited in neutral and acidic aqueous media. Although an unequivocal definitive mechanism is not known, a possible explanation consistent with the experimental observations is suggested.