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| Naji, M. |
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| Motta, Antonella |
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| Aletan, Dirar |
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| Mohamed, Tarek |
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| Ertürk, Emre |
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| Taccardi, Nicola |
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| Kononenko, Denys |
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| Petrov, R. H. | Madrid |
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| Alshaaer, Mazen | Brussels |
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| Bih, L. |
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| Casati, R. |
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| Muller, Hermance |
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| Kočí, Jan | Prague |
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| Šuljagić, Marija |
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| Kalteremidou, Kalliopi-Artemi | Brussels |
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| Azam, Siraj |
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| Ospanova, Alyiya |
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| Blanpain, Bart |
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| Ali, M. A. |
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| Popa, V. |
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| Rančić, M. |
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| Ollier, Nadège |
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| Azevedo, Nuno Monteiro |
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| Landes, Michael |
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| Rignanese, Gian-Marco |
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Cruz, Carlos
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Publications (7/7 displayed)
- 2022Chiral 1D Metal-Organic Materials Based on Cu(II) and Amino Acid Schiff Basescitations
- 2022Synthesis and characterisation of ionic liquid crystals based on substituted pyridinium cationscitations
- 2021Study of magnetoelastic resonance for chemical sensors: Ribbons vs microwirescitations
- 2010Shear-induced lamellar ionic liquid-crystal foamcitations
- 2007Structure and molecular dynamics of the mesophases exhibited by an organosiloxane tetrapode with strong polar terminal groupscitations
- 2006Characterization by fourier transform infrared spectroscopy (FT-IR) and 2D IR correlation spectroscopy of PAMAM dendrimercitations
- 2002Anisotropic hydroxypropylcellulose films as alignment layers of a bistable ferroelectric devicecitations
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article
Structure and molecular dynamics of the mesophases exhibited by an organosiloxane tetrapode with strong polar terminal groups
Abstract
The polymorphism of a new organosiloxane tetrapode compound with cyano terminal polar groups was characterized by means of polarizing optical microscopy and x-ray diffraction. The compound exhibits smectic-A and smectic-C phases with a partial bilayer arrangement due to a certain degree of head-to-head association of the mesogenic units through their cyano end groups. On the basis of x-ray diffraction results, evidencing the microsegregation of polyphilic molecules, packing models for the smectic-A and smectic-C phases are proposed. A high degree of smectic positional order and a relatively low value of the tilt angle in the smectic-C phase are indicated. Molecular dynamics of the studied compound was investigated by means of proton NMR relaxometry. The frequency dispersions of the spin-lattice relaxation time (T-1) show that the relaxation is induced by three rotational modes of individual dendrimer arms with frequencies between 10(6) and 10(9) Hz. In the smectic phases, the effect of individual rotations is overwhelmed by a well expressed contribution of layer undulations at Larmor frequencies below similar to 10 MHz. The appearance of this relaxation mechanism over the frequency range of three decades is so far unique in the case of thermotropic liquid crystals. The analysis of the layer undulations contribution supports the microsegregation model of the smectic phases by revealing a slowing-down of translational diffusion and the lack of interactions among the sublayers formed by the mesogenic groups.