A series of new hydrolytically stable poly(carbobetaine)s was synthesised varying the length and the position of the hydrophobic side chains, together with their cationic analogues. The synthetic strategy avoids the presence of residual salt in the polybetaines, thus making them well suited for model studies. The betaine monomers as well as their cationic analogues bearing the equivalent of an undecyl chain exhibit surfactant properties ("surfmers"). The corresponding polymers, however, which are formed by cyclopolymerisation, are insoluble in water, though hygroscopic. In contrast, the hydrophobic chains favour the solubility in alcohols and allow the formation of superstructures in bulk. The poly(carbobetaine)s form homogeneous blends with selected inorganic salts, to provide organic-inorganic hybrid materials. (C) 2001 Elsevier Science Ltd. All rights reserved.