NMR Characterization of Liquid Crystal—Polymer Interactions in Polymer-Dispersed Liquid Crystals

Abstract

Solid-state nuclear magnetic resonance (NMR) and optical microscopy have been used to study liquid crystal–polymer interactions in polymer-dispersed liquid crystals (PDLCs) composed of the E7 liquid crystal mixture and poly(n-butyl methacrylate) or poly(isobutyl methacrylate). As previously reported, the droplets adopt a bipolar configuration in the PDLCs using poly(n-butyl methacrylate) as the matrix material and a radial configuration in those using poly(isobutyl methacrylate). The NMR signals from the E7 cannot be detected in the bulk state by using magic angle spinning and cross-polarization because of its liquid-like properties. The E7 and the polymer signals are only weakly cross-polarized in 60:40 E7/poly(n-butyl methacrylate) PDLCs but are strongly cross-polarized in the PDLCs with poly(isobutyl methacrylate). We suggest that the differences are due to a change in the surface-anchoring conditions and that NMR spectroscopy may provide a molecular-level probe of the forces that control droplet configuration and the electro-optical properties of these materials.