Stimulated resonance between electrical and shear fields by a colloid system

Abstract

CERTAIN polymer solutions have been shown using a Couette shear dielectric cell¹ to exhibit changes in dielectric properties when subjected to a shear field^2,3. For polar polymers which lack flexibility, the qaction of a rotational shear field alters the time-dependent distribution of dipole orientation which results in changes of permittivity, loss magnitude and relaxation frequency². In quantitative terms these changes seem to correspond well with the theoretical treatment due to Barisas⁴. A distinct difference in the situation occurs when flexible polymers such as poly(styrenes) or poly(p-ethoxystyrenes) are subjected to such shear fields. The changes are inconsistent with the magnitude of the polymer dipole and solvent relative permittivity takes on a rather dominant role³. To test the importance of variation of the internal field term on shape changes due to polymer coil distortions, we have studied an organic colloid system: cross-linked poly(ethylacrylate) dispersed in heptane and stabilised with a ‘comb’ graft copolymer [poly-(12-hydroxy stearic acid) terminated with glycidyl methacrylate and then copolymerised (1:1) with methyl methacrylate]⁵.