Trithiocarbonate-mediated free-radical photopolymerization: improved uniformity in hologram recording

Abstract

A holographic material based on a photopolymerizable nematic acrylate was improved by the addition of the trithiocarbonate, EtO2CCH2SC(S)SCH2CO2Et, increasing uniformity and reproducibility in the formation of electrically switchable holographic gratings. Diffraction efficiencies as high as 34%, the thin-grating theoretical maximum, were achieved at large (10-14 microm) grating spacings. Improved diffraction efficiency was seen over a range of grating spacings (0.35-10 microm). The exposure window for grating formation was increased by an order of magnitude, resulting in much improved reproducibility.

Ionic Liquids in Photopolymerizable Holographic Materials

“…The spatial frequency increasing leads to the decreasing of the diffraction efficiency. These results are similar to the hologram material based on a photopolymerizable nematic acrylate [20]. Figure 6c-f shows the optic images of the gratings.…”

Ionic liquid as additive to increase sensitivity, resolution, and diffraction efficiency of photopolymerizable hologram material

“…The exposition time has been reduced to approximately 4-5 s comparable to the composites without ionic liquids, and the diffraction efficiency increased smoothly after stopping the exposition ͑see supporting information, 7 Figs. 8 As can be seen from the above results, ionic liquid as additive efficiently improves the sensitivities and increases the diffraction efficiencies of the photopolymer hologram materials. The ionic liquids BMIMBF 4 and 1-octyl-3-methylimidazolium tetrafluoroborate ͑OMIMBF 4 ͒ with BF 4 − as anion gave rise to better diffraction efficiencies than the ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate ͑BMIMPF 6 ͒ and 1-octyl-3-methylimidazolium hexafluorophosphate ͑OMIMPF 6 ͒ with PF 6 − as anion ͑see Table I͒ ͑composites 2 and 7 and composites 10 and 13͒.…”

Application of ionic liquids in photopolymerizable hologram materials

“…Photopolymerizable holographic materials due to their practical use in memories and optical elements, have attracted a interest in academics and industry [1,2]. The photopolymerizable holographic composite contains mainly a matrix binder, a photopolymerizable monomer, an initiator system, a plasticizer and additives [3].…”