Direct Measure of the Tilt Angle in de Vries‐Type Liquid Crystals through NMR Spectroscopy

Marchetti, Alessandro; Domenici, Valentina; Novotná, Vladimı́ra; Lelli, Moreno; Cifelli, Mario; Lesage, Anne; Veracini, Carlo Alberto

doi:10.1002/cphc.201000116

Cited by 19 publications

(50 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The analysis of the spectra recorded at 7.05 T (Figure 4 and ref [33].) showed a behaviour very similar to common ferroelectric smectogens [35].…”

mentioning

confidence: 64%

“…In this respect, NMR gave a contribution with several studies [18,27,33,34] performed on a rod-like 'de Vries' compound, namely 9HL (see Figure 4). One of the most fascinating properties of 'de Vries' systems is the absence of layer-shrinkage at the SmA-SmC* transition, coupled with a high response to the electric field in the SmA phase, the so called electroclinic effect.…”

Section: A Case Study: a 'De Vries' Liquid Crystal Investigated By Mementioning

confidence: 91%

“…The first NMR work on 9HL was performed on a selectively deuterated compound with two equivalent deuterons on a phenyl ring of the aromatic core [33], as reported in Figure 4. 2 H NMR spectra were recorded by varying the temperature from the isotropic to the SmC* phase and, due to the presence of a single type of deuterons, the spectra are extremely simple (see Figure 4).…”

Section: 1mentioning

confidence: 99%

“…In the isotropic phase, the 2 H NMR spectrum is characterised by a single peak, due to the Zeeman interaction. In the SmA and SmC* phases, the anisotropy is at the origin of the typical spectral shape, constituted by a large doublet, Δν q ranging from 13.5KHz to~17.5KHz (due to the 2 H quadrupolar interaction) that further splits in a small doublet, Δν d ranging from~1.1KHz to~1.8KHz (due to the 1 H-2 H dipolar interaction) [33]. The relationships among the measured quadrupolar, Δν q , and dipolar, Δν d , splittings and the molecular orientational order parameters, S ii , are in general quite complex; however, in this case, several approximations can be introduced.…”

Section: 1mentioning

confidence: 99%

“…H NMR investigations at different magnetic fields to get information about the supramolecular structure of the 'de Vries' phase A determinant contribution to understand the supramolecular properties of the 9HL in the SmA and in the SmC* phases, came from the 2 H NMR study at several magnetic field strengths [33,34]. In fact, as reported in Figure 5, different behaviours were observed in the two mesophases by increasing the magnetic field.…”

mentioning

confidence: 99%

See 4 more Smart Citations

Nuclear magnetic resonance: a powerful tool to study liquid crystals

Domenici

2017

Liquid Crystals Today

Self Cite

View full text Add to dashboard Cite

Nuclear magnetic resonance (NMR) is a spectroscopic technique widely used to investigate materials and soft matter in particular. In this brief review, the main uses of NMR techniques to investigate different aspects of liquid crystals, such as the orientational and dynamic properties, the supramolecular structure and average molecular conformations, are described. In the second part of the paper, the case study of a 'de Vries' liquid crystal is reported and the main results obtained by combining different NMR techniques are discussed. ARTICLE HISTORY

show abstract

“…The analysis of the spectra recorded at 7.05 T (Figure 4 and ref [33].) showed a behaviour very similar to common ferroelectric smectogens [35].…”

mentioning

confidence: 64%

Section: A Case Study: a 'De Vries' Liquid Crystal Investigated By Mementioning

confidence: 91%

Section: 1mentioning

confidence: 99%

Section: 1mentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Nuclear magnetic resonance: a powerful tool to study liquid crystals

Domenici

2017

Liquid Crystals Today

Self Cite

View full text Add to dashboard Cite

show abstract

Azo Monomers Exhibiting Low Layer Shrinkage at the SmA–SmC Transition and trans–cis Light‐Induced Isomerization

et al. 2012

View full text Add to dashboard Cite

Methacrylic monomers containing a (phenylene)azobenzene unit substituted with a lateral cyano group and alkyl chains of different length are synthesized and characterized by NMR techniques. Their liquid-crystalline properties are studied by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction. All monomers exhibit a mesomorphic behavior that extends over wide temperature ranges with nematic and orthogonal or tilted smectic-type mesophases, depending on the length of the terminal chain. The smectic structures are determined to be single-layered with a low layer shrinkage (<5 %) at the SmA-SmC transition. This atypical behavior is attributed to the combination of a high smectic order promoted by both π-π and bond dipole-bond dipole interactions between cyano-substituted central cores, and a low correlation between neighboring layers arising from dispersive forces between the end groups (methacrylic group and alkyl chain) of the monomer. On the other hand, the trans-cis isomerization of monomers is induced in solution by irradiating with a UV lamp. High cis-isomer contents (≥96 %) are obtained at the photostationary state, which is reached in a relatively short time (40 s).

show abstract

Conformational Properties and Orientational Order of a de Vries Liquid Crystal Investigated through NMR Spectroscopy

et al. 2014

Self Cite

View full text Add to dashboard Cite

Solid-state and liquid-state NMR spectroscopic techniques are used to describe at molecular level the behaviour of a de Vries liquid crystal (namely the mesogen 9HL) at the SmA-SmC* transition, which is characterized by the absence of the layer shrinkage, typical of non-de Vries smectogens. Previous (2)H NMR studies on the same smectogen, performed at a different magnetic field (from 4.70 to 18.80 T), provided evidence of the occurrence of a tilt of one of the three phenyl rings, constituting the aromatic core of 9HL, at the SmA-SmC* phase transition. In this work, the study is extended to the whole rigid aromatic core of the 9HL. In particular, the variable temperature behavior of the mesogen studied by 1D (13)C NMR cross-polarization (CP) and 2D (1)H-(13)C PDLF (proton-encoded (13)C-detected, local field) NMR experiments made possible the characterization of the conformational and orientational properties in the two smectic phases. These results are compared with various proposed models invoked to describe the SmA-SmC* transition in de Vries smectogens at a molecular level.

show abstract

Direct Measure of the Tilt Angle in de Vries‐Type Liquid Crystals through NMR Spectroscopy

Abstract: communication

Cited by 19 publications

References 41 publications

Nuclear magnetic resonance: a powerful tool to study liquid crystals

Nuclear magnetic resonance: a powerful tool to study liquid crystals

Azo Monomers Exhibiting Low Layer Shrinkage at the SmA–SmC Transition and trans–cis Light‐Induced Isomerization

Conformational Properties and Orientational Order of a de Vries Liquid Crystal Investigated through NMR Spectroscopy

Contact Info

Product

Resources

About