HYDROGELS BASED ON WATER-SOLUBLE POLY(ETHER URETHANES) DERIVED FROM L-LYSINE AND POLY(ETHYLENE GLYCOL)

Water-soluble poly(ether urethanes) (M(w) up to 170 000) have been prepared by the copolymerization of bis(succinimidyl) carbonate derivatives of poly(ethylene glycol) (PEG) with L-lysine (Lys) m a strictly alternating fashion. The resulting copolymers have physical properties similar to those of PEG while the carboxylic acid groups Of L-lysine provide multiple pendent groups along the polymer backbone for further functionalization. By using PEG chains of different molecular weights, a homologous series of PEG-Lys copolymers was prepared containing one lysine unit every 1000, 2000, 4000, and 8000 Da. The pendent carboxylic acid groups were utilized in cross-linking reactions leading to amide cross-links, new acyl semicarbazide cross-links, and hydroxyethyl acrylate and hydroxyethyl methacrylate derived cross-links. The resulting hydrogels formed transparent, highly swollen films. At an equilibrium water content of about 80%, these films exhibited a relatively high degree of tensile strength ranging from 0.26 to 1.09 MPa. Due to their favorable physicomechanical properties and the nontoxicity of the components, PEG-Lys-derived hydrogels may find applications as biomaterials.