Dicholesteryl icosanedioate as a glass-forming cholesteric liquid crystal: properties, additive effects and application in color recording

A cholesteric ester dimer – dicholesteryl icosanedioate – was examined for color imaging. Cholesterol was introduced as one of the dopants which performed an important role reducing phase transition temperatures. The other dopants, 4,4′-dialkoxyazobenzene and 4,4′-dialkoxybiphenyl promoted formation of smectic domains in cholesteric phases which resulted in the expansion of the reflective band shift over the whole visible region. In particular, the photo-responsive dopant 4,4′-dialkoxyazobenzene allowed us to realize reversible RGB color tuning of the cholesteric film by both photon and thermal modes. The trans–cis photoisomerization led to a cholesteric pitch change which resulted in reflective color change, and recorded optical images that have been stable for more than 8 months in a glassy solid film state.