Novel Cinnamate Esters—Synthesis and Mesomorphic Properties in Relation to Molecular Structure

A novel homologous series 4-[4′-n-alkoxy cinnamoyloxy] benzyl cinnamates consisting of 11 homologs was synthesized and studied with a view to understanding and establishing the relation between molecular structure and mesomorphic behavior of a substance. Mesomorphic behavior of the series commences from the third homolog and then continues until the last hexadecyloxy homolog. The first and second members of a series are non-mesomorphic. Nematogenic mesophase formation is observed from the propoxy homolog to the hexadecyloxy homolog, but the smectogenic mesophase formation is observed from the hexyloxy homolog to the tetradecyloxy homolog. All mesomorphic transitions are enantiotropic in nature. Transition temperatures were determined by an optical polarizing microscopy equipped with a heating stage. The textures of the nematic mesophase are threaded or Schlieren in type and that of the smectic mesophases are focal conic fan shaped of the smectic A or smectic C type. A phase diagram of the series shows a normal behavior of the transition curves with a minor abnormality of the last three homologs for the nematic-isotropic transition curve. The average thermal stability for smectic and nematic mesophases is 176.0°C and 219.3°C, respectively. Analytical and spectral data agree with the molecular structures of homologs. Mesomorphic phase length varies between 22°C and 76°C. Smectic phase length varies from 6°C to 33°C and nematic phase length varies from 22°C to 54°C. Thus, the novel present series is predominantly nematogenic and partly smectogenic. Mesomorphic properties of the novel series are compared with structurally similar other known homologous series.     

Chemical reaction kinetics leading to the first Stober silica nanoparticles – NMR and SAXS investigation

²⁹Si-NMR and ¹³C-NMR were used in methanol and ethanol to monitor the intermediates or hydrolyzed monomers that lead to the formation of the first primary particles as detected by small angle X-ray scattering. This identification was facilitated by using initial NH₃ and H₂O levels at the lower end of those experienced in Stober synthesis to slow the reaction kinetics. We found that [NH₃] and [H₂O] control the balance between hydrolysis of tetraethylorthosilicate (TEOS) and the condensation of its hydrolyzed monomers. Transesterification between methanol and TEOS did occur; however, it was negligible compared to the production of hydrolyzed intermediates. The first nanostructures appear at a hydrolyzed monomer concentration around 0.1 M, indicating that formation of the primary structures is thermodynamically controlled by a supersaturation of the intermediate species. Differences in particle size between methanol and ethanol are attributed to thermodynamic interactions between the solvent and the hydrolyzed intermediates.     

Relation Between Structure and Mesogenic Activity in α,α′-Dimethylbenzalazines Influence of Intramolecular H-Bonding (II)

The central molecular geometry of three series of benzalazines: 4,4′-Dialkoxy-α,α′-Dimethylbenzalazines, 4,4′-dialkoxy-2,2′-dihydroxy-α,α′-Dimethylbenzalazines, and 4,4′-dialkoxy-2-hydroxy-α,α′-Dimethylbenzalazines was studied by U.V., I.R., and ¹H.N.M.R. spectroscopy.

All the compounds studied show the E-E configuration. The intramolecular H-bond between the nitrogen of the azine central group and the H of the OH group in position 2 of the aromatic ring is “exceptionally” strong in accordance with the calculations made using Schaefer's equation. This bond conditions the geometry of the molecules, as well as their mesogenic properties. The intramolecular H-bonding favors the formation of mesophases whose properties are also related to the number of bonds of this type which the molecules contain.     

Specific Features of Microstructure Formation in Co–Cr–Ni–W–Ta Alloys and Their Mechanical Properties

Crystallography Reports - The microstructure and mechanical properties of three experimental compositions of a new heat- and corrosion-resistant cast cobalt-based alloy have been investigated. It...     

Structural Features of Mixed Anions (Мо7 – хWхO24)6– and Their Packing in the [Pd(NH3)4]3(Мо7 – хWxO24)⋅6H2O Crystal Structure

Crystallography Reports - [Pd(NH3)4]3(Мо7 – хWxO24)?6H2O crystals with different Mo/W ratios have been formed as a result of the crystallization of a...     

Molecular Dynamics Simulation of the Structure and Ion Transport in the Ce<Subscript>1 – <Emphasis Type="Italic">x</Emphasis></Subscript>Gd<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>2 – δ</Subscript>|YSZ Heterosystem

Molecular dynamics simulation has been used to develop a realistic atomistic model of two-layer Ce_{1 – x}Gd _x O_{2 – δ}|YSZ heterosystem. It is shown that Ce_{1 – x}Gd _x O_{2 – δ} and YSZ layers (about 15 and 16 Å thick, respectively) retain their crystal structure on the whole. The main structural distortions are found to occur near the Ce_{1 – x}Gd _x O_{2 – δ}|YSZ geometric interface, within a narrow interfacial region of few angstroms thick. Both the generalized diffusion characteristics of the system as a whole and the oxygen diffusion coefficients in the layers are calculated, and the diffusion activation energies are determined.