Molecular dynamics, conductivity and morphology of sodium deoxycholate-based poly(ester ether)urethane ionomer biomaterials

Broad-band dielectric spectroscopy technique was used to investigate the molecular dynamics of new sodium deoxycholate-based poly(ester ether)urethane ionomers of particular interest in biomedical devices. These polyurethane ionomers have identical hard segment containing bile salt moiety but with different soft segment chemistries. Poly(ethylene oxide)-rich soft segment promotes stronger ionic interactions and solvation capacity of ions and higher ionic conductivity in these polyurethane ionomers. The universal power law was employed to study the evolution of alternating conductivity (AC) with frequency and temperature. The calculated values of fractional exponent ranged between 0 and 1 which indicate AC conduction through hopping mechanism. Direct current conductivity evidences Arrhenius behaviour in the function of temperature and the estimated values of activation energy for poly(ethylene oxide)-rich soft segment polyurethane ionomers are found higher. The increase in the conductivity with temperature can be interpreted as a hopping mechanism assisted by chain relaxation. AFM and SAXS investigations evidence lamellar arrangement at the sub-micron scale and the nanophase-separated morphology for these polyurethane ionomers. The tensile tests evidenced that the polyurethane with highest molecular weight exhibits the highest values of mechanical properties and ductile behaviour.