AMPHIPHILIC URETHANE ACRYLATE HYDROGELS HAVING HETEROPHASIC GEL STRUCTURE - SWELLING BEHAVIORS AND MECHANICAL-PROPERTIES

Amphiphilic urethane acrylate hydrogels containing ionic group (dimeth ylopropionic acid, DMPA) were prepared by varying the molecular weight of the soft segment (polyether type, PTMG) and type of diisocyanate, and their swelling behaviors and mechanical properties were examined. They showed amphiphilic property due to the hydrophilic ionic groups a nd hydrophobic polyethers comprising the urethane acrylate network. He terophasic gel structure could be found for the hydrogels prepared in water, but not for the hydrogels in organic solvent (1,4-dioxane), thr ough scanning electron microscopy. Because of this heterophasic gel st ructure, they were able to take in a large amount of water as well. Th e hydrophobic interaction generated by the polyether soft segments bet ween urethane acrylate network chains decreased the degree of swelling , however, increased reversibly the tensile strengths at equilibrium s welling state. MDI-based hydrogel showed low swelling ratio and high t ensile strength because of its ordered hard domain structure. These am phiphilic urethane acrylate hydrogels showed salt-and pH-dependent swe lling behaviors.