square mm is much higher for sample a than for sample b this can be observed in the histogram and from inspection of the micrographs the lc domain densities are 26 lc domains per square mm for sample a and 20 lc domains per square mm for sample b to characterize the electro optical properties of the pdlc samples the threshold voltage at which the optical transmission passes from the off state to the on state using a single 0 5 second pulse with increasing field amplitude was determined the optical region for electro optical measurements with low cell damage was in the 1 06 to 1 33 mv m range a long duration square pulse at high field strength applies a dc field across the material for most of the pulse duration and may cause electrochemical degradation of the organic material even in the absence of radiation the long duration pulses were therefore not used light transmission data through both sample a and sample b were measured using crossed polarization conditions a 0 5 second 1 2 mv m square pulse induced a significant effect due to lc director orientation the resulting optical signal was recorded and is shown in fig4 which shows the time dependent optical response of the cell these data represent the time evolution of the lc director orientation along the direction of the applied field this response was observed to be characteristic of both sample a and sample b a qualitative description of the physical phenomena causing the electro optical response in fig4 relies on elliptical polarization of light transmitted through the cell application of the 1 2 mv m pulse decreases the birefringent behavior of the cell as the lc director.