EFFECT OF CROSS-LINKING DENSITY ON THE PHYSICAL-PROPERTIES OF INTERPENETRATING POLYMER NETWORKS OF POLYURETHANE AND 2-HYDROXYETHYL METHACRYLATE-TEMINATED POLYURETHANE

Interpenetrating polymer networks (IPNs) of 2-hydroxyethyl methacrylat e-terminated polyurethane (HPU) and polyurethane (PU) with different c rosslinking densities of the PU network were prepared by simultaneous solution polymerization. Dynamic mechanical analysis (DMA) and differe ntial scanning calorimetry (DSC) show that compatibility of component polymers in IPN formation depends on the crosslinking density of the P U network. Physical properties such as density and water absorption re ly on the subtle balance between the degree of phase separation and th e crosslinking density of the PU network. In spite of the occurrence o f phase separation, the tensile moduli and tensile strength of the IPN s increase with the crosslinking density of the PU network. Morphologi cal observation by scanning electron microscopy revealed different fra cture surfaces between the compatible and incompatible IPNs. Surface c haracteristics of the IPNs, indicated as hydrogen bonding index and ha rd-to-soft segment ratio, are altered considerably by varying surface morphologies. Improved blood compatibility of IPN membranes is due to the variation of the hydrophilic and hydrophobic domain distribution.