46. Thote, Amol; Gupta, Ram, B.
Hydrogen-bonding of a Dichroic Dye with a Liquid Crystal for Application to
LCDs. Fluid Phase Equilibria (2004), 220(1),
47-54.
Abstract
The performance of guest-host type liq. crystal displays
(LCDs) is governed by the soly. and dissoln. stability of dichroic dyes in the
liq. crystal medium in guest-host kind of LCDs.
The soly. and stability is influenced by hydrogen-bonding between the
dye and the liq. crystal host. An
earlier work was carried out to study the hydrogen-bonding behavior of
4-pentyl-4'-cyanobiphenyl (5CB) (liq. crystal), benzonitrile, and acetonitrile,
with 1-hexanol in CCl4 using FTIR spectroscopy, ab initio and equation of state
calcns. [Ind. Eng. Chem. Res. 42 (2003)
1129]. To gain further thermodn.
understanding, hydrogen-bonding behavior of 5CB (liq. crystal), benzonitrile,
and acetonitrile, with a dichroic dye Disperse Red 1 (DR1)
{2-[ethyl[4-[(4-nitrophenyl)azo]phenyl]amino]ethanol} in CCl4 were studied in
this work. In all three mixts., -OH acts
as a hydrogen-bond donor and -CN acts as hydrogen-bond acceptor. Based on FTIR anal. for DR1/acetonitrile,
DR1/benzonitrile, and DR1/5CB, the enthalpies of hydrogen-bond formation are
-24.2, -23.7, and -3.7 kJ/mol, resp.; and the entropies of hydrogen-bond
formation are -58.9, -58.1, and -0.4 J/(mol K), resp. Though, for DR1/5CB, enthalpy of H-bonding is
not too neg., the entropy of H-bonding is more favorable; hence the H-bonding
appears to be entropically driven.
Lattice fluid hydrogen-bonding (LFHB) parameters obtained from the
spectroscopic data were obsd. to match well with the exptl. trends. LFHB equation of state was then used to
predict hydrogen-bonding for a wider range of conditions.
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