Interpretation of proton NMR lineshape of liquid crystals

Schmiedel, H.; Hillner, B.; Grande, S.; Lösche, A.; Limmer, St.

doi:10.1016/0022-2364(80)90260-7

Cited by 14 publications

(16 citation statements)

References 4 publications

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“…appointing e jk = e z {e jk and e : denote the corresponding unit vectors) one can rewrite the angular dependent term of (2) as follows: where SHH represents the order parameter of the Z-axis (= line connecting protons j and k) with respect to the direction of the magnetic field (characterized by unit vector e^). S^h can now be described in terms of three traceless tensors H k/ , Sffl, and K%p [12] by…”

Section: General Expression For the Second Moment Of The Proton Nmr Lmentioning

confidence: 99%

“…Using the before-mentioned (LM/WSD model we simulated the angular dependence of the proton NMR lineshapes in the smectic-C phases of Oct-OAB and Hept-OAB with tilt angles of 30° (Oct-OAB) and 37.5° (Hept-OAB), resp., starting from the spectra for 0 = 0 which were computed by employing the procedure described and applied in [12,14,17] (cf. Figs.…”

Section: Maximum Polarization -Validity Of Thementioning

confidence: 99%

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Proton NMR Investigations of the Smectic-C Phases of Three Alkyloxy-Azoxybenzenes

Limmer

Findeisen

1983

Zeitschrift Für Naturforschung A

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Proton NMR investigations of the smectic-C phases of three 4,4'-bis-/?-alkyloxy-azoxybenzenes (C 7 , C 8 , C 9 ) with temperature independent tilt angles are presented.The behaviour of well-aligned samples (strong magnetic field ^ 1.5 T, slow cooling rate) under rotation in the field can be described by the models of Luz and Meiboom, and Wise, Smith, and Doane, (LM/WSD), resp. However, on polarization of the samples in presence of magnetic fields ^ 0.75 T the molecular directors are not arranged preferentially parallel to the direction of the polarizing magnetic field but are rather inclined, i.e., the layers are stacked preferentially perpendicular to the original magnetic field direction (PSL model). It is shown that all the angular dependences of NMR second moments can be interpreted in terms of a superposition of the LM/WSD and PSL models, or, on the other hand, by assuming totally disordered fractions of the samples together with portions that fully obey the behaviour demanded by one of the above models (LM/WSD or PSL). The tilt angles derived from the comparison of experimental and theoretical angular dependences of the second moments for well-aligned samples are applied to the explanation of the experiments at lower polarizing fields successfully, too.

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Section: General Expression For the Second Moment Of The Proton Nmr Lmentioning

confidence: 99%

Section: Maximum Polarization -Validity Of Thementioning

confidence: 99%

Proton NMR Investigations of the Smectic-C Phases of Three Alkyloxy-Azoxybenzenes

Limmer

Findeisen

1983

Zeitschrift Für Naturforschung A

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“…For the calculation of the proton NMR spectra as described in detail formerly [1,2] we have used the co-ordinates from the crystal structure analysis of TBBA by Doucet et al [8] adding a third proton at the third chain carbon of the TBBA molecule and omitting the terminal methyl group of TBBA. In the crystalline state (and therefore our TBPrA model) the TBBA molecule adopts nearly a "eis" conforma tion of the three phenyl rings.…”

Section: Simulation Of the Proton Nmr Spectramentioning

confidence: 99%

“…At first we tried to fit the theoretical spectra with only one set of 0. (P and mere variation of the conformational parameters * Sj [1][2][3] which approxi mately describe the degree of reduction of dipolar interactions of the proton spins with their nearest neighbours. However, it turned out after many fruitless attempts that this was impossible.…”

Section: Axis Throughmentioning

confidence: 99%

“…The comparison of simulated and experimental proton NMR spectra has been successfully exploited to make assertions concerning the intramolecular mobility and conformation of molecules in meso phases [1][2][3]7]. In all cases hitherto reported on, the proton NMR lineshape did not change signif icantly even when smectic phases were involved [7], i.e.…”

Section: Introductionmentioning

confidence: 99%

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Proton NMR Studies and Lineshape Simulations of the Mesophases of Terephthalylidene -Bis -4 -n-propylaniline (TBPRA) — Evidence for Conformational Changes

Limmer

Findeisen

1984

Zeitschrift Für Naturforschung A

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From comparison of simulated and experimental spectra in the nematic, smectic-A, and smectic-C phases of TBPrA it can be concluded that there are conformational changes of the molecule giving obviously rise to a continuous variation of the direction of the long molecular axis with respect to a frame of reference connected with a conformation of the molecule that was derived from the crystal conformation of TBBA.

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