New fabrication approach to develop a high birefringence photo-crosslinked film based on a sulfur-containing liquid crystalline molecule with large temperature dependence of birefringence

ABSTRACT

We present a new fabrication approach to achieve a high birefringence film by means of photopolymerization based on an alkylthio-containing rod-like liquid crystalline molecule exhibiting large temperature dependence of birefringence. We designed a new reactive mesogen having alkylthio linkages (BPM–S). It was found that BPM–S had a larger increment of birefringence with decreasing temperature, relative to commercially available alkoxy analog LC242. This result could be thought to be due to enhanced intermolecular attractive interaction for an alkylthio mesogen implied by the proximity of laterally neighboring molecules and cybotactic nematic tendency based on wide-angle X-ray measurement. The uniaxially-aligned photo-polymerized film for BPM–S showed higher birefringence than that for LC 242.

KEYWORD:

• Alkylthio group
• high birefringence
• nematic phase
• photocrosslinking
• photopolymerization

Additional information

Funding

This study was partly supported by JSPS KAKENHI grant number 15H06285 and 17K14493, a research grant from the Nitto Foundation, and Toyota Physical and Chemical Research Institute Scholars.