SEQUENTIAL POLYURETHANE-POLY(METHYLMETHACRYLATE) INTERPENETRATING POLYMER NETWORKS AS URETERAL BIOMATERIALS - MECHANICAL-PROPERTIES AND COMPARATIVE RESISTANCE TO URINARY ENCRUSTATION

The mechanical properties and resistance to urinary encrustation of se quential interpenetrating polymer networks (IPNs) composed of polyuret hane (PU) and polymethylmethacrylate (PMMA), have been described. Mech anical properties were determined using tensile testing and dynamic me chanical analysis, whereas resistance to encrustation was examined usi ng an in vitro model for encrustation simulating in vivo encrustation. Maximum and minimum tensile strength at break, Young's modulus, stora ge and loss moduli were associated with PMMA and PU, respectively. IPN s demonstrated intermediate mechanical properties which were dependent on the concentrations of the component polymers. Conversely, maximum elongation at break was observed for PU and this parameter decreased a s the concentration of PMMA increased in the IPN. The dynamic mechanic al damping parameter, tan delta, was similar for all IPNs at 37 degree s C. Increased advancing and decreased receding contact angles were ob served for IPNs in comparison with the native PU. The rate and extent of encrustation, measured as the percentage surface coverage, was simi lar for PU, IPNs and PMMA. In contrast, encrustation on polyhydroxyeth ylmethacrylate, a model hydrogel, was greater than observed for the IP Ns or component polymers. No apparent correlation was observed between the rate and/or extent of encrustation and polymer contact angle. It is concluded that these IPNs may be of clinical benefit in patients pr oviding stent resistance to extrinsic compression of the ureter in com parison with native PU. The comparable resistance to encrustation betw een the IPNs and PU indicates:that the use of IPNs should not be restr icted in this regard.