Determination of the Molecular Arrangement in Liquid Crystals by Polarization of Fluorescence

Долганов, В. К.; Bolotin, B. M.

doi:10.1080/00268947808083742

Cited by 16 publications

(5 citation statements)

References 3 publications

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“…5. We can see that f4 (9) at the temperature corresponding to the nematic phase is significantly broadened with respect to f4 (9) determined in the smectic phase.…”

Section: Molecular Orientationmentioning

confidence: 63%

“…(1) one can obtain the tuncated distribution function f4 (9), where In Fig. 5 the distribution functions f4 (19) for 8CB doped with the dye II in the smectic (T* = 0.951) and nematic (T* = 0.976) phases are plotted.…”

Section: Resultsmentioning

confidence: 99%

“…Experimental determination of the orientational order parameters for guest--host mixtures is usually carried out using the polarized absorption and/or fluorescence spectroscopies [6][7][8][9][10][11][12][13][14][15]. Previously, we had used the measurements of polarized absorption and fluorescence spectra of a pleochroic dye dissolved in some low molecular liquid crystals [14] and doped to side chain liquid crystal polymers [13,15] in order to obtain information about the molecular orientation in the ne -m a t i c p h a s e .…”

Section: Introductionmentioning

confidence: 99%

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Orientational Behaviour of the Guest-Host Systems in the Smectic A and Nematic Phases

1992

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The measurements of the polarized absorption and fluorescence components spectra for the guest-host mixtures have been used to study the long orientational order in the uniaxial phases of the liquid crystal. The temperature dependence of the order parameters, (Ρ2) and (Ρ 4 ), has been investigated and the molecular distribution function has been determined. On the basis of the (Ρ2) and (Ρ4), values some conclusions about the molecular orientation in the smectic A and nematic phases of the liquid crystalline samples have been drawn. It has been also found that the fluorescence spectroscopy is a sensitive method for determination of the phase transition temperatures of the liquid crystal doped with the fluorescent dye.

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“…5. We can see that f4 (9) at the temperature corresponding to the nematic phase is significantly broadened with respect to f4 (9) determined in the smectic phase.…”

Section: Molecular Orientationmentioning

confidence: 63%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Orientational Behaviour of the Guest-Host Systems in the Smectic A and Nematic Phases

1992

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“…Badley, Martin & Schneider (1973) have studied a number of chromophores solubilized in lecithin lipid bilayers, and a review has been written on fluorescence techniques in the study of biological systems (Badley, 1976). Some reports have appeared where the orientation of a chromophore in thermotropic liquid crystals has been determined (Cehelnik et al 1976;Dolganov & Bolotin, 1978;Chapoy & DuPre", 1979). The latter authors studied the orientation of 4-dimethylamino-4'-nitro-stilbene embedded in the liquid crystals p-metoxybenzlidenep'-n-butylaniline (MBBA).…”

Section: (B) Proteins In Biological Membranesmentioning

confidence: 99%

Orientation and mobility of molecules in membranes studied by polarized light spectroscopy

Johansson

Lindblom

1980

Quart. Rev. Biophys.

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Biological membranes are composed of mainly lipids and proteins. The physical properties of the lipids, forming a bilayer structure, are of crucial importance for the living cell, since the plasma membrane is the guardian barrier towards the environment. Thus, the functioning cell needs a highly stable lipid bilayer, which depends on molecular packing and orientation properties of the various membrane components (Wieslander et al. 1980). The spatial arrangement of the membrane proteins incorporated in the lipid matrix plays an essential role for the different chemical processes occurring at or within the membrane. Information about molecular orientation and mobility is therefore necessary for unravelling the functional mechanisms of a biological membrane.

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“…A great number of experimental papers have been presented (see [6,13] for a set of references) and the technique is now at a stage of being optimized, rather than pioneered. Various steady state experiments exist for nematics [17][18][19][20][21][22][23], but as far as we are aware there is in contrast only one experimental paper on time resolved fluorescence depolarization in thermotropic liquid crystals [24]. Cehelnik et al [24] studied all trans 1,6 diphenyl hexatriene (DPH) in a compensated cholesteric mixture formed by cholesteryl chloride and laurate.…”

Section: Introductionmentioning

confidence: 99%

Time resolved fluorescence depolarization in a nematic liquid crystal

et al. 1987

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A time dependent fluorescence depolarization experiment is reported and fully analysed for the first time for a probe dissolved in an aligned nematic liquid crystal. We have investigated the popular dye all trans 1,6 diphenyl hexatriene in the transparent mesophase mixture ZLI-1167 at a series of temperatures within the nematic and isotropic range. The probe order parameter (P2) and perpendicular rotational diffusion coefficient have been determined, together with the fluorescence lifetime ZF in the liquid crystal and isotropic phase. This information is extracted applying a previously proposed theory for rotational fluorescence depolarization in a mesophase , Molec. Phys., 38, 1813 and introducing a global variant of the target analysis deconvolution procedure presented earlier (ARCIONI, A., and ZANNONI) C., 1984, Chem. Phys., 88, 113). Our results demonstrate the possibility of employing fluorescence depolarization as a useful technique for investigating aligned mesophases. IntroductionThe theory needed to interpret time resolved fluorescence depolarization experiments [1, 2] in a liquid crystal [3] has been around for some time now [4]. This theory gives a molecular interpretation to time dependent fluorescence polarization intensities by assuming molecular reorientation to be the dominant depolarizing mechanism. The theoretical intensities are then expressed in terms of static and dynamic quantities, i.e. orientational order parameters and correlation functions [4]. For the simplest case of a rigid probe with effective cylindrical symmetry dissolved in a uniaxial mesophase the orientational order parameters are given by the infinite set of Legendre polynomial averages (PL) = (PL( cos fl)), where fl is the angle between the cylinder axis of the molecule and that of the mesophase [5]. A fluorescence depolarization decay experiment can yield in favourable conditions the first two non-trivially vanishing order parameters, i.e. (P2) and (P4) I'4, 6]. What can be obtained in practice from a certain experiment is predicted to depend on the relative times scales of the fluoresence decay and reorientation process ZF and ZR. Let us consider, to be specific, a rod-like probe molecule [7] with absorption and emission transition moments p and ~ parallel to the long molecular axis. In this case the fourth rank order parameter (P4) for the probe can be obtained when the fluorescence time ZF is much shorter than the long axis correlation time ~o. On the other hand if ZV is much longer than Zo, so that the photoselected molecules have enough time to relax to orientational equilibrium, only the second rank Legendre polynomial average (P2) can be reliably obtained. The maximum amount of information can be extracted from experiments where the time dependence of fluorescence depolarization is followed. There, in fact, orientational correlation functions Downloaded by [McMaster University] at 02:

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Determination of the Molecular Arrangement in Liquid Crystals by Polarization of Fluorescence

Cited by 16 publications

References 3 publications

Orientational Behaviour of the Guest-Host Systems in the Smectic A and Nematic Phases

Orientational Behaviour of the Guest-Host Systems in the Smectic A and Nematic Phases

Orientation and mobility of molecules in membranes studied by polarized light spectroscopy

Time resolved fluorescence depolarization in a nematic liquid crystal

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