Chapter 4: Electron Beam Curing of Monomer/Liquid Crystal Blends
Published:03 Jan 2019
M. Bouchakour, Y. Derouiche, Z. Bouberka, C. Beyens, P. Supiot, F. Dubois, ... U. Maschke, in Polymer-modified Liquid Crystals, ed. I. Dierking, The Royal Society of Chemistry, 2019, ch. 4, pp. 45-60.
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This chapter focuses on a comparison of two polymerization/crosslinking methods to produce polymer/liquid crystal (LC) systems: rapid UV-visible irradiation and high voltage accelerated electron beams (EB), with comparable exposure times. The comparison was performed in terms of some physical properties such as phase diagrams, polymerization and phase separation kinetics, morphologies, and electro-optical responses. During polymerization and crosslinking, the longer the spacing between the two acrylic double bonds or the higher the molecular weight, the more rapid was the monomer conversion under UV-light; however, the reverse was found for EB-curing. The PDLC films produced by EB curing had more homogenous and regular morphologies. The electro-optical responses of various PDLC systems showed significant differences between the UV-cured samples and those cured by EB. It was found that the driving voltages considerably increased in the case of the UV-cured systems. For the contrast ratios, which are important for applications, EB-cured systems confirm their higher quality. Moreover, EB curing leads to considerable monomer conversions without a photoinitiator which may act as an impurity that might have negative impact on the electro-optical performance of the obtained PDLC films.