Bilirubin is the end product of heme catabolism in man and most animals and is ultimately excreted into the bile.' The compound has a low solubility in aqueous media. Almost all of the bilirubin transported in the blood is tightly bound to serum albumin.' It is assumed that charged residues of histidine, arginine, and tyrosine are involved in the binding,3 while one lysine group is close to the binding site.4 The nature of the binding of bilirubin to serum albumin is still unknown, although recent data suggest that salt linkages and hydrogen bonds rather than hydrophobic interactions are the main factors in the binding.5Recently, we prepared6 two polymers (Scheme I) with an imidazole ring in each repeating