Rhc. Janssen et al., Cholesteric thermo-reversible liquid-crystal gels: Phase behaviour and electro-optical response, JPN J A P 1, 40(4A), 2001, pp. 2372-2377
Thermo-reversible gels of a chiral nematic liquid-crystal (LQ with 12-hydro
xyoctadecanoic acid (HOA) were cast in a light-reflecting planar configurat
ion by choosing a processing temperature higher than the sol-gel temperatur
e but lower than the onset-temperature for the chiral nematic-isotropic tra
nsition in the gel. The choice of processing temperature is dictated by the
quasi-ternary phase diagram of the system, which displays a 3-phase region
at which an isotropic liquid is in equilibrium with a fibrillar solid and
a chiral nematic mesophase. Planar configurations of the gels produced show
a significant broadening of the reflection band with respect to the neat L
C-material indicating a distribution of the cholesteric pitch within the ge
l. Visco-elasticity, electro-optical activity and zero electric field bista
bility of gelled films has been utilized in building a reflective bistable
chiral nematic cell with improved shock-resistance that holds the promise o
f being produced via a continuous processing route.