Stable photoalignment layer for nematic liquid crystals based on ladder-like polysilsesquioxanes

A new kind of aligning material for liquid crystal cells, ladder-like polys ilsesquioxanes (LPS) grafted with cinnamoyl side groups, has been developed to improve the thermal stability of the photoalignment layer. The LC align ing ability of the LPS-based alignment layers, fabricated by linearly polar ized W-induced polymerization (LPP), was characterized by polarizing optica l microscopy, conoscopic observations and electro-optic response measuremen ts. In particular, a practical and severe annealing test was adopted to exa mine the thermal stability of the alignment layer; this showed that even wh en LC cells were annealed at 100 degrees C (much higher than the clearing p oint of the Ld) for several hours, good LC orientation could remain when th e cell was cooled to a constant measurement temperature. The results confir med that the photoalignment layers exhibited not only good LC aligning abil ity, but also excellent thermal stability, so heralding their potential app lication in LCDs.