Urethane modified polyethers as homogeneous electrorheological materials

Urethane modified polyethers having hard-soft-hard or soft-hard-soft struct ure were prepared by addition of isocyanate compounds and polyether glycols . It was found that a hard-soft-hard polymer prepared from polypropylene gl ycol and naphthalene diisocyanate shows an increase of viscosity in an elec tric field (positive electrorheological effect), while a soft-hard-soft pol ymer prepared with the same starting materials shows a decrease of viscosit y (negative electrorheological effect). Viscosity measurements and NMR rela xation analyses of monodisperse model compounds were also performed to cons ider the mechanism of these opposite effects. Comparison of H-1-NMR relaxat ion times of modified and unmodified polyether indicated that the rapid mod e of molecular motion is enhanced by the modification while the slow mode i s restricted. The change of molecular movement by the modification of polye ther is considered to play some role in the enhanced electro-responsive pro perty.