Urethane Modified Polyethers as Homogeneous Electrorheological Materials

Abstract

Urethane modified polyethers having hard-soft-hard or soft-hard-soft structure were prepared by addition of isocyanate compounds and polyether glycols. It was found that a hard-soft-hard polymer prepared from polypropylene glycol and naphthalene diisocyanate shows an increase of viscosity in an electric field (positive electrorheological effect), while a soft-hard-soft polymer prepared with the same starting materials shows a decrease of viscosity (negative electrorheological effect). Viscosity measurements and NMR relaxation analyses of monodisperse model compounds were also performed to consider the mechanism of these opposite effects. Comparison of 'H-NMR relaxation times of modified and unmodified polyether indicated that the rapid mode of molecular motion is enhanced by the modification while the slow mode is restricted. The change of molecular movement by the modification of polyether is considered to play some role in the enhanced electro-responsive property.

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