Molecular Motion Analysis of E7 in PDLCs as a Function of Droplet Size Using Solid-State 13 C NMR Relaxation Spectroscopy

Abstract

¹³C NMR relaxation spectroscopy as applied to polymer-dispersed liquid crystals (PDLCs) provides a method for measuring the molecular motions of the liquid crystal molecules within droplets dispersed throughout the material's polymer matrix. Because liquid crystal molecular motion may play a major role in the switching phenomenon of PDLC materials from an opaque film to a clear film, both T₁ and T₁ρ relaxation experiments are used to measure molecular mobility of the liquid crystal as a function of droplet size for PDLC materials made of E7 and epoxy. The segmental molecular motions measured by T₁ρ relaxation show a significant dependence on liquid crystal droplet size. Three models are provided which explain the observed restriction in segmental mobility of the liquid crystal molecules as the droplet size decreases and the polymer/liquid crystal interaction increases.