The well-known polymer, polysulfone (PS), was used, via its carboxylated derivative, as a carrier vehicle for low-molecular weight substances (haptens). The synthesis and characterization of conjugates of PS-CO(2)H (1) coupled to a relatively non-immunogenic aliphatic hapten (2) or an aromatic hapten (3) and various intermediates in their syntheses, are reported. Immunization with 1, 2, and 3 afforded anti-hapten antibodies and, interestingly, provided evidence for significant adjuvant activity by 1 and related substances. Further studies are called for in order to understand the mechanism of action and correlate immune activity with structure, but these initial results indicate the intriguing possibility of novel immunization methods, free of conventional, toxic adjuvants. (C) 2002 Elsevier Science B.V. All rights reserved.