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.


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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