PHASE-STRUCTURE CHANGE AND ER EFFECT IN LIQUID-CRYSTALLINE POLYMER DIMETHYLSILOXANE BLENDS/

The mechanism of the electrorheological (ER) effect in two types of li quid crystalline polymer (LCP)/dimethylsiloxane (DMS) blends was inves tigated by rheological measurements and by structure observation under electric field and shear flow. The results show that the phase struct ures of these immiscible blends can be categorized into slipping (low viscosity) and non-slipping (high viscosity) states. In the non-slippi ng state, higher viscosity LCP domains connect the electrodes. In the slipping state, on the other hand, LCP domains do not connect the elec trodes and the shear is mainly confined in the lower viscosity DMS dom ains. The ER effect (electrically induced viscosity increase) originat es from the electrically induced slipping to non-slipping transition. In one of the blends, the ER effect occurs only at high shear rate, si nce this blend is in non-slipping state even under no field if the she ar rate is low.