Molecular motions and ordering of the interfacial, droplet and binder regions of polymer dispersed liquid crystal displays: A paramagnetic resonance spin probe study

The molecular dynamics and ordering of polymer-dispersed liquid-crystal displays are studied using the technique of paramagnetic resonance of spin probes. A complex spectrum is observed in which components are identified from probes dissolved in the droplet, binder, and interfacial regions of the display. In particular, the liquid-crystal curing, phase separation, and structure of displays with both thermoplastic and epoxy binders are investigated. Observations are also performed as the liquid-crystal droplet size is varied. Among the more interesting results is the demonstrated ability to observe the interfacial region. It appears to be quite fluid and has little or no average order. It is also observed that the compatibility between the binder and liquid crystal, seen from some of the formulations studied, correlates with the reported electro-optical properties. These include the magnitude and hysteresis of switching voltages and the magnitudes of switching times.