ELECTRICALLY-INDUCED REVERSIBLE STRUCTURAL-CHANGE OF A HIGHLY SWOLLEN POLYMER GEL NETWORK

By using high-intensity X-rays from a synchrotron radiation source the structural response of a non-ionic polymer gel of poly(vinyl alcohol) (PVA) in dimethyl sulfoxide to the application of an electric field has been investigated. The gel used as the electroactive gel actuator showed an excellent response: There was an increase of 8% in relative strain within ca. 200 ms at an electric field strength of 2.5 x 10(5) V m(-1). To clarify the initial stages of this electrically induced actuating phenomenon, scattering experiments were carried out in the range of the electrically induced relative strain below 0.8%. As shown by the scattering curves, the application of the electric field barely affected the long-range structure of the gel, but induced a reversible change in the scattering curve corresponding to a dimension of period ca. 60 Angstrom. Both the analysis of the distribution of distances and the estimate of correlation lengths imply local structural change over the above length scale when an electric field is applied. The present results suggest that the application of an electric field to a non-ionic gel can induce a reversible rearrangement of polymer chains around chemical crosslinking points to create a local scattering density fluctuation which provides a macroscopic effect.