T. Sagisaka et Y. Yokoyama, Reversible control of the pitch of cholesteric liquid crystals by photochromism of chiral fulgide derivatives, B CHEM S J, 73(1), 2000, pp. 191-196
When an enantiomer of resolved indolylfulgide (1) or either of the (R)-bina
phthol-condensed indolylfulgides (2, 3) was mixed with a nematic liquid cry
stal (5CB), the cholesteric phase was induced. Their cholesteric pitches we
re reversibly changed by photoirradiation. Whereas the twisting ability of
the cholesteric pitch (beta(M)) was larger for the colorless form than for
the colored form in the case of 1, it was larger for the colored form than
for the colorless form in the cases of 2 and 3. In addition, beta(M) of 1 i
s generally smaller than that of 2 and 3. These phenomena were explained in
terms of the helical conformation of the hexatriene moiety of fulgides and
the chirality of the binaphthol moiety.
The cholesteric sense of a fulgide-doped liquid crystal was changed between
plus and minus reversibly by the pre-doping of the chiral formaldehyde ace
tal of 1,1'-bi-2-naphthol ((S)-4).