Search results for "liquid"

Liquid crystals in the series of 2,4,6-tristyryl-1,3,5-triazines

2004

Abstract Alkaline condensation reactions of 2,4,6-trimethyl-1,3,5-triazine ( 1 ) and substituted benzaldehydes ( 2a – n ) yield 2,4,6-tristyryl-1,3,5-triazines ( 3a – n ). A sufficient number and length of the alkoxy chains at the benzene rings provide liquid crystalline phases Col hd . A special structure was found for compound 3i with 9 hexyloxy chains; it exists in the solid state in a helical columnar arrangement, which is transformed by heating to a hexagonal columnar mesophase. Irradiation of the mesophases of 3i – 3m leads to partial cyclodimerization reactions, which cause different textures and lower the clearing points. The border line between the irradiated and the unirradiated z…

Second harmonic generation in ferroelectric liquid crystalline thiadiazole derivatives

1995

Structure and Dilution of Mesogenic Side Chains in Liquid Crystalline Polysiloxanes

1988

Abstract The structure of the smectic phases in four series of homo- and copolymers based on dimethylsiloxane chains with a definite variation of the concentration of the paired mesogenic side chains has been investigated by means of X-ray methods. The dilution of the mesogenic moiety was achieved by insertion of additional dimethylsiloxane segments. A nearly linear dependence of the layer spacings on the dilution has been found. A model of the structure is proposed which consists of two sublayers one of which contains the irregularly arranged main chain whereas the other one is formed by the side chains.

1986

The molecular order and mobility of two liquid-crystalline polyacrylates with phenyl benzoate moieties as mesogenic side groups and (CH2)m spacers (m = 2 and m = 6) were investigated by pulsed 2H NMR. The mesogenic side groups were isotopically labelled at the terminal phenylene ring. In the glassy state the orientational distribution function was characterized from the angular dependence of the 2H NMR line shape of samples macroscopically ordered in their nematic phase by the 8,4 T magnetic field of an NMR spectrometer. It was found to be Gaussian with widths of ± 18,5° and ± 10,5° for the m = 2 frozen nematic and m = 6 frozen smectic system, respectively. The phenylene rings undergo 180° …

The Phase Behaviour of Amphiphilic Monolayers

1991

Amphiphilic monolayers display a wealth of condensed phases. It is only recently that these have been widely recognised as being distinct, but they are in fact quite analogous to the well-known lamellar gel phases of bulk lyotropic and thermotropic mesogens. An understanding of these phases has proved to be important for controlling the defect structure of the monolayers used in the fabrication of Langmuir-Blodgett films. This understanding is being achieved by developments in a number of techniques, including X-ray diffraction and isotherm miscibility. The phase diagrams of the materials studied so far are all very closely related, lending new credibility to the principle of corresponding …

Mesomorphic Donor-Acceptor-substituted 1,4-Distyrylbenzenes

2009

Conjugated oligomers with terminal donor-acceptor substitution attract increasing attention in organic chemistry because of their outstanding and not seldom unexpected properties in materials science [1 – 4]. Although a variety of oligo(1,4-phenylene-vinylene)s with terminal donor-acceptor substitution (DAOPVs 1, Scheme 1) are known [5 – 22], the number of thermotropic liquid crystals among them is very low and is confined to monomers (n = 1), that means to certain push-pull substituted (E)-stilbenes [23 – 31]. The behavior of conjugatedmolecules, which are highly polar and form mesophases by self-organization, is very interesting for various applications of liquid crystals [3]. A big disad…

Synthesis of Tripyreno[2,3,4-abc: 2,3,4-ghi: 2,3,4-mno][18]annulenes

2000

The title compounds were prepared in a multi-step synthesis in which primarily the pyrene building blocks were formed (1,2 11a,b). The final reaction step 11a,b 12a,b consisted of a threefold trans selective cyclocondensation process that generated the central 18-membered ring. Hexyloxy or dodecyloxy sidechains attached on the periphery led to the formation of liquid crystalline phases.

Compensation. Compte courant, Solde créditeur, Dette certaine au titre de l'engagement de caution de la banque (oui), Exigibilité (non), Connexité (o…

1996

International audience; (Com. 6 févr. 1996, Mme de Thore ès qual. c/ BNP, D. 1997.353, note D. Boccara)

Compensation. Créances connexes. Dette de TVA antérieure au jugement d'ouverture et crédit de TVA généré par des opérations postérieures. Connexité (…

1999

International audience; (Com. 19 janv. 1999, Mme Du Buit, ès qual. c/ Receveur principal des impôts de Palaiseau Nord)

Compensation. Garantie à première demande souscrite par une banque. Contre-garantie à première demande fournie par une autre banque. Débiteur garanti…

2001

International audience; (Com. 6 mars 2001, Gladel et Beauquis c/ Sté Générale)