Twisted phase gratings induced by photoregulated mesogenic molecules on the surface of photoreactive polymer liquid crystal film

Abstract

Three-dimensional phase gratings with twisted structures were self-organized by photoregulated mesogenic molecules on the surface of photocrosslinkable polymer liquid crystal film. The molecules are selectively photoreacted only at the surface of the film under the polarization holographic illumination, and the resultant photocrosslinked mesogenic molecules induce the three-dimensional twisted gratings in the film during annealing process. The diffraction properties were well explained by means of Jones calculus and diffraction theory.

Twisted Molecular Reorientation by Axis-Selective Surface Photoreaction and Subsequent Self-Organization in Photocrosslinkable Polymer Liquid Crystals

“…Axis-selective photoreaction was performed using LP He-Cd laser beams, which emit a 325 nm light. From our previous observation, the absorption coefficient is about 4:3 Â 10 4 cm À1 at a wavelength of 325 nm 42) and this value is sufficiently high to absorb the incident light near the surface. Figure 1 shows the geometry of the exposure of writing beams adopted in this study.…”

“…Because of the large induced anisotropy originating in the cooperative reorientation of LC molecules, photosensitive liquid crystalline polymeric materials are emerging as a very important class of functionalized materials to be used for generating the necessary photoinduced optical anisotropy for optoelectronics. [1][2][3][4][5][7][8][9]12,13,15,16,[18][19][20][21][22][23][25][26][27][28][29]31,32,[35][36][37][38][39][40][41][42][43] We have reported on photocrosslinkable polymer liquid crystalline (PPLC) films containing cinnamate groups, which reveal a stable molecular orientation. [35][36][37][38][39][40][41][42][43] One merit of cinnamate derivatives is their transparency in the visible region, which is important for display applications and functionalized optical devices.…”

“…[1][2][3][4][5][7][8][9]12,13,15,16,[18][19][20][21][22][23][25][26][27][28][29]31,32,[35][36][37][38][39][40][41][42][43] We have reported on photocrosslinkable polymer liquid crystalline (PPLC) films containing cinnamate groups, which reveal a stable molecular orientation. [35][36][37][38][39][40][41][42][43] One merit of cinnamate derivatives is their transparency in the visible region, which is important for display applications and functionalized optical devices. During the course of our systematic study of PPLC films that show a photoinduced molecular orientation, we found that polymethacrylates with 4-(4-methoxycinnamoyloxy)biphenyl (MCB) side groups exhibit efficient in-plane molecular reorientations.…”

“…We have reported that the three-dimensional twisted reorientation can be fabricated by surface photoreaction and the cooperative reorientation of mesogenic molecules. 42) Three-dimensional phase gratings with twisted structures were self-organized by photoregulated mesogenic molecules on the surface of a PPLC film. The molecules are selectively photoreacted only at the surface of the film under polarization holographic illumination, and the resultant photocrosslinked mesogenic molecules induce the three-dimensional twisted gratings in the film during the annealing process.…”