16 December 2004 Effect of adding a multifunctional acrylate on the electro-optical properties of reflection gratings formed by thiol-ene photopolymerization
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Abstract
Thiol-ene photopolymerization reactions initiated by a UV Argon laser line were used to write Bragg reflection gratings in polymer dispersed liquid crystals. Thiol-ene polymers are well suited as hosts for grating formation as they exhibit good long-term stability in their optical and electro-optical properties. Gelation in thiol-enes occur at high conversions (> 50%) and phase separation leads to formation of spherically shaped nematic droplets. For conventional photopolymerization using acrylates, high molecular weight polymer is formed very early in the reaction and therefore gelation occurs at low conversions. In this study, we have observed the effect of adding a multifunctional acrylate to the commercially available Norland thiol-ene precursors on the formation of Bragg reflection gratings. The results suggest a preferential homopolymerization of acrylate leading to early gelation that adversely affects the performance of the reflection gratings. A decrease of diffraction efficiency, an increase of switching voltage, and higher levels of shrinkage of the polymerizing film was observed. Morphology studies indicate with increasing addition of acrylate, a progressive transition from spherical nematic droplets to elongated droplets occurs with decrease of droplet density.
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Lagudi Natarajan, Lagudi Natarajan, Jay Klosterman, Jay Klosterman, Vincent P. Tondiglia, Vincent P. Tondiglia, Richard L. Sutherland, Richard L. Sutherland, Pamela F. Lloyd, Pamela F. Lloyd, Timothy J. Bunning, Timothy J. Bunning, } "Effect of adding a multifunctional acrylate on the electro-optical properties of reflection gratings formed by thiol-ene photopolymerization", Proc. SPIE 5621, Optical Materials in Defence Systems Technology, (16 December 2004); doi: 10.1117/12.579365; https://doi.org/10.1117/12.579365
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