ZWITTERIONIC POLYMERS .2. SYNTHESIS OF A NOVEL SERIES OF POLY(VINYLBETAINES) AND THE EFFECT OF THE POLYMERIC STRUCTURE ON THE SOLUBILITY BEHAVIOR IN WATER

Four novel poly(vinylbetaines) have been prepared by polymerization of the corresponding monomers. The monomers were obtained by alkylation of a tertiary amine with α- and γ-halocarboxylic acids and addition to acrylic acid. The zwitterionic polymer derived from bromoacetic acid exhibited the usual solubility characteristics, i.e. insoluble in water but soluble in dilute sodium chloride solutions. By contrast, the zwitterionic polymer derived from α-bromopropanoic acid was found to be soluble in water and in 0-2 M sodium chloride solutions. This result can be explained by assuming the operation of a steric effect on intrasalt interactions in the macromolecule. The zwitterionic polymers derived from acrylic acid and γ-bromobutanoic acid are also soluble in water and in sodium chloride solutions. The differences in solubility behaviour are rationalized in terms of differences in pKas of the betaine moiety. By changing the pH of the polymer solution, the solubility characteristics of a poly(vinylbetaine) can be changed from those of polyzwitterions to those of a polyelectrolyte. © 1990.