Photoalignment layers for liquid crystals from the di-$π$-methane rearrangement.

TitlePhotoalignment layers for liquid crystals from the di-$π$-methane rearrangement.
Publication TypeJournal Article
Year of Publication2013
AuthorsCox, JR, Simpson, JH, Swager, TM
JournalJournal of the American Chemical Society
Date Publishedjan
Keywordsphotoalignment liq crystal dimethane rearrangement

Photoalignment of nematic liquid crystals is demonstrated using a di-$π$-methane rearrangement of a designed polymer. The alignment mechanism makes use of the strong coupling of the liquid crystal directors to dibenzobarrelene groups. The large structural changes that accompany photoisomerization effectively passivate segments of the polymer, allowing the remaining dibenzobarrelene groups to dominate the director alignment. Photoisomerization requires triplet sensitization, and the polymer was designed to have a uniaxially fixed rigid structure and rapid triplet energy transfer from the proximate benzophenone units to the dibenzobarrelene groups. The isomerization was observed to be regiospecific, and thin films showed alignment.