We have examined the morphology of polymer-dispersed liquid-crystal materials (PDLCs), which show great potential for display applications. The materials were blends of a eutectic nematic liquid-crystal (LC) mixture and a UV-cross-linkable polymeric matrix and were examined in thin films. A variety of morphologies ranging from two-phase, polymer-dispersed LC droplets, to single-phase nematic spherulites was obtained depending upon composition and irradiation temperature. The effects of irradiation dose were also investigated. Scanning electron micrographs show that the LC drops depart significantly from sphericity and can have fused or satellite droplets, as well as bimodal size distributions in the 0.2-8-mu m range. The spherulitic morphologies (which predominate following UV irradiation above 10 degrees C for 25% LC to above 65 degrees C for 60% LC) start from a central s = +1 disclination line and grow through accretion of LC molecules in a tangential orientation. Profuse radially oriented defects were identified as surface inversion walls; they appear to be initiated by factors both inherent to the spherulite and external (e.g., surface influences and local compositional variations). These inversion walls are consistently initiated at s = +1/2 disclination lines (and not at s = -1/2) and are reoriented parallel to the boundaries at the points of spherulitic impingement even though their local molecular orientation remains unchanged. They, as well as the overall spherulitic morphology survive heating above the nematic-to-isotropic transition (and subsequent cooling), with the exception of the regions near the interspherulitic boundaries, where some rearrangement of inversion-wall features is observed.
