Synthesis and aqueous solution behaviour of copolymers containing sulfobetaine moieties in side chains

A two-step method was developed to synthesize sulfobetaine copolymers with different comonomer units in the main chain. The alternating copolymers, po ly(N-vinyl-2-pyrrolidone-co-phthalimidoacrylate) and poly(styrene-co-phthal imidoacrylate) were modified with 3-dimethylaminopropylamine to yield copol ymers containing tertiary amine groups in the side chains. They were then q uaternized with 1,3-propanesultone. The aqueous solution behaviour of the z witterionic copolymers depended on the structure of the backbone. Thus, the copolymer derived from the N-vinyl-2-pyrrolidone-based precursor dissolved only in aqueous salt solutions. The reduced viscosities of these solutions were insensitive to the polymer concentration. Increasing the salt concent ration and "softness" of the salt ions slightly increased the intrinsic vis cosity. The results suggest the important role of the intramolecular intera ctions in the solution behaviour of this sulfobetaine copolymer. In contras t, the sulfobetaine copolymer containing styrene units in the main chain fo rmed micellar solutions whose intrinsic viscosity decreased on salt additio n. (C) 1999 Elsevier Science Ltd. All rights reserved.