Three types of elastomeric segmented polyurethanes represented by a polyether-urethane, a polyurethane-urea, and a polycarbonate-urethane were introduced into a modified low-temperature variant of base-induced N-alkylation of urethane hard segments with an excess of 1,6-dibromohexane in N,N'-dimethylacetamide (DMAc), resulting in the modification of polymers with 0.08-0.26 mmol/g of pendant 6-bromohexyl groups. Either lithium diisopropylamide (LDA) or sodium hydride was used to initiate the reaction, although LDA was found to be more suitable for the bromoalkylation. Selected bromoalkylated polyurethanes of all three types were reacted with thiol-containing bisphosphonates, to yield the polymers modified with 0.08-0.12 mmol/g of geminal nonesterified covalently attached bisphosphonate groups. Two thiol-containing geminal bisphosphonates used in the modifications were prepared via reactions of nucleophilic addition to vinylidene-bisphosphonic acid. All three types of polyurethanes were found equally suitable for the modifications. The bisphosphonate-modified polyurethanes with nonmetallic cations on the bisphosphonate groups remain soluble in the solvents suitable for the dissolution of nonmodified polymers and can be processed into films by solvent casting. After the exchange of nonmetallic cations to sodium, the polymers become insoluble in any solvent, probably as a result of the intermolecular coordination of bisphosphonate groups with the metal cations. (C) 2000 John Wiley & Sons, Inc.