Contribution of Fluorescence Spectroscopy to the Determination of Binary Phase Diagrams of Mesomorphic Mixtures. Part II. Investigation of the Induced Smectic A1Phase of the System Nonylcyanobiphenyl/ Phenylcyclohexanecarboxylate
- 1 March 1989
- journal article
- liquid crystals
- Published by Taylor & Francis in Molecular Crystals and Liquid Crystals Incorporating Nonlinear Optics
- Vol. 168 (1), 37-62
- https://doi.org/10.1080/00268948908045959
Abstract
The fluorescence intensity and the wavelength distribution of binary mesomorphic mixtures composed of 4-nonyl 4′-cyanobiphenyl (9CB) and 4-pentylphenyl 4′-cyclohexane carboxylate (5H5) have been recorded as a function of the temperature in the isotropic, nematic and induced smectic mesophases (SA1, SB and SG). Two types of fluorescence can be observed in these systems: monomer fluorescence and excimer fluorescence. Their intensity ratio ranges from 0 to ∞ as a function of the composition, of the temperature and of the nature of the phase involved. Monomer fluorescence (IM) is characteristic of materials of low molecular mobility and high degree of order. It is found in SB and SG mesophases. Excimer fluorescence (ID) on the other hand is predominantly observed in less-ordered and more fluid phases like SA1, nematic and isotropic phases. It has been shown in this work that band shape modifications and shifts of the LD max of the fluorescence spectra can be related to changes in the relative importance of radiative and non-radiative deactivation processes of the excited state and that intensity changes allow us to detect phase transitions. A new type of isoemissive point which has the nature of the phase as the variable parameter has also been discovered for these mixtures.Keywords
This publication has 8 references indexed in Scilit:
- Influence of molecular organization on the photophysical properties of two alkylcyanobiphenylsJournal de Chimie Physique et de Physico-Chimie Biologique, 1986
- Structure bicouche des mésophases SA et SB du 4-cyanobutoxybenzylidene-4-octylanilineJournal de Physique, 1986
- Contribution of the fluorescence spectroscopy to the determination of binary phase diagrams of mesomorphic mixtures. I. Investigation of a system-alkylcyanobiphenyl/phenyl-cyclohexanecarboxylateJournal de Physique, 1986
- Conjectures sur le comportement smectique A des mésogènes dissymétriques et fortement polairesJournal de Physique, 1984
- Luminescence studies in polymers—I: Temperature effect on polyvinylnaphthalene and polyacenaphthylene fluorescenceEuropean Polymer Journal, 1972
- On the interpretation of iso-emissive pointsChemical Physics Letters, 1971
- Isosbestic points in emission spectraChemical Physics Letters, 1968
- ‘Excimer’ fluorescence V. Influence of solvent viscosity and temperatureProceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences, 1964