Title

Processing-structure-property relationships of a polymer-templated cholesteric liquid crystal exhibiting dynamic selective reflection

Date of Award

2012

Degree Name

M.S. in Materials Engineering

Department

Department of Chemical and Materials Engineering

Advisor/Chair

Advisor: Charles Edward Browning

Abstract

Cholesteric liquid crystals (CLCs) are chiral-structured materials that exhibit selective reflection color. While methods to switch off this color with external stimuli have been established, the use of external stimuli to change the reflection color is currently under development. This work explores processing-structure-property relationships of a polymer-templated CLC system that exhibits large-scale reflection color changes with temperature. The effects of heating rate, curing intensity, and cell geometry on the magnitude of these color changes were investigated by collecting transmission spectra of the system during heating and cooling. The system exhibited a constant color change of 500-600 nm at heating rates up to 10°C/min. Samples cured at intensities below 1.00 mW/cm² displayed larger color changes. The cell geometry was largely unaffected by the cell thickness. However, for cell thicknesses between 10 and 50 μm, as cell thickness increased, the magnitude of the color change decreased. The potential impact of attaching, or tethering," the chiral-structured polymer/liquid crystal gel to the cell surface was also considered. Both tethered and untethered systems displayed large-scale color changes with temperature."

Keywords

Polymer liquid crystals Effect of high temperatures on, Polymer liquid crystals Spectra, Reflection (Optics), Materials science; cholesteric liquid crystal; chiral-structured polymer network; gel phase transition; dynamic coloration; photopolymerization; response kinetics

Rights Statement

Copyright 2012, author

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