Broadband polarizing films by photopolymerization-induced phase separation and in situ Swelling

Abstract

This letter describes the spectral broadening of cholesteric liquid crystal films prepared from a blend comprising a cross-linkable liquid crystal polymer and a noncross-linkable low-molecular-weight liquid crystal. The bandwidth of the broadened reflection band can be increased by several times upon photopolymerization. The spectral broadening arises from the formation of gradient pitch across the film thickness. It is shown that both phase separation and in situ swelling are important mechanisms for the resulting film structure.

Surface anchoring effects on spectral broadening of cholesteric liquid crystal films

“…11 The region closest to the UV light source that had the longest pitch can be explained by the fact that the more cross-linked region was swollen by the nonreactive LC. Swelling of polymerized planar CLC films by LC ͑Ref.…”

“…Both polymerization-induced phase separation and in situ swelling are essential to the broadening of the reflection band under the conditions of fixed film thickness and fixed molecular orientation at substrate interfaces. 11 This paper reports the effects of surface anchoring on the spectral broadening.…”

Enhancement of polarization properties of reflective composite sheet

“…This results in higher brightness and improved energy efficiency. Polarizers of this type include nanowire grids [2,3], cholesteric liquid crystal (CLC) films [4], randomly dispersed-type scattering polarizers [5,6], and multilayer-type reflective polarizers [7][8][9][10][11][12][13].…”

Cholesteric liquid crystal gels with a graded mechanical stress

“…This geometry is in perfect agreement with the helical structure as shown by SEM. The explanation that states the pitch is larger in regions rich in nematic compounds (a nematic structure looks like a cholesteric structure with an infinite pitch) [4][5][6]8,11,13,14] is not valid. Most of the studies focusing on light reflection broadening as the consequence of the generation of a polymer gradient have used nematic monomers and transmission spectra.…”