New poly(carbobetaine)s made from zwitterionic diallylammonium monomers

A series of new hydrolytically stable poly(carbobetaine)s with varying distance between the ammonium and the carboxylate group was synthesized, excluding the presence of residual salt in the polymers, together with cationic and sulfobetaine analogues. The poly(carbobetaine)s show improved solubility compared to analogous poly(sulfobetaine)s, and are more hygroscopic. Their thermal stability depends strongly on the length of the spacer group separating the ammonium and the carboxylate group. The poly(carbobetaine)s are typically amorphous, but for long spacer groups, they exhibit a superstructure. They are capable of forming homogeneous blends with a number of inorganic salts, following the selectivity of the Hofmeister series, thus giving access to new organic-inorganic hybrid materials.