Stimulated resonance between electrical and shear fields by a colloid system

CERTAIN polymer solutions have been shown using a Couette shear dielectric cell1 to exhibit changes in dielectric properties when subjected to a shear field2,3. 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.