Peculiarities of pluronic crystallization in thin films

The peculiarities of the crystallization of Pluronics from chloroform and aqueous polymer solution on mica surfaces are investigated with the atomic force microscopy method. It is shown that Pluronics in thin films form quasi two-dimensional crystalline structures of 10–12 nm thickness. Pluronic crystallization proceeds predominantly via the mechanism of diffusion-limited aggregation with the formation of dendrites. Three main morphological types of formed structures are identified including two types of dendrites (with 45° and 90° angles between branches) and elongated “needles.” It is shown that the film morphology depends on the polymer concentration, rate of solvent evaporation, and, probably, local gradients of concentration and temperature. Interaction with porphyrins establishes conditions for the local three-dimensional crystallization of Pluronics.     

Synthesis of 4,6-Disubstituted 2-Thioxo-1,2-dihydropyridine-3-carbonitriles by the Reaction of Acetylenic Ketones with Cyanothioacetamide

Russian Journal of General Chemistry - The reaction of acetylenic ketones with cyanothioacetamide in the presence of morpholine yields 4,6-disubstituted...     

Synthesis and Properties of 4,6-Dimethyl-5-pentyl-2-thioxo-1,2-dihydropyridine-3-carbonitrile and 3-Amino-4,6-dimethyl-5-pentylthieno[2,3-b]pyridines

The reaction of 3-pentylpentane-2,4-dione with cyanothioacetamide afforded 4,6-dimethyl-5-pentyl-2-thioxo-1,2-dihydropyridine-3-carbonitrile. Alkylation of the latter led to the formation of 2-alkylsulfanyl-4,6-dimethyl-5-pentylpyridine-3-carbonitriles or 3-amino-4,6-dimethyl-5-pentylthieno[2,3-b]pyridines, depending on the alkylating agent and reaction conditions. The structures of the key compounds were proved by 2D NMR spectroscopy and X-ray analysis. Biological activity of the synthesized compounds was evaluated in silico. Some compounds were experimentally found to stimulate growth of sunflower seedlings.

     

Propagation of light through a forbidden zone in chiral media

The particular features of the propagation of light in uniaxial chiral liquid crystals with a large pitch of the spiral are considered. There exist forbidden zones in these systems for fairly large angles of incidence of an extraordinary ray. On the one hand, this results in an efficient reflection of the wave from the zone boundary, and, on the other hand, this causes the wave to decay inside the zone. A case of narrow forbidden zones is studied, and it is shown that optical effects that arise upon propagation of rays near turning points are equivalent to the tunnel and over-barrier reflection effects. The angular dependences of the intensities of rays that were refracted in a forbidden zone and transmitted through it are calculated. The percolation effect is experimentally studied in a mixture of a nematic liquid crystal with a chiral addition. The intensity of a transmitted extraordinary ray is studied as a function of the angle of incidence, which determines the width of the forbidden zone. Both the over-barrier reflection and the percolation effects are observed. The calculation results are shown to agree with experiment.     

Experimental and Theoretical Study of Spectroscopy of Binuclear Difluoroborate Dipyrromethene Complexes

Russian Physics Journal - The spectroscopic characteristics of mono and binuclear difluoroborate complexes of dipyrromethenes in various solvents and solid-state polymer media (films) are...     

Synthesis,Structure, and Analgesic Activity of 4-(5-Cyano-{4-(fur-2-yl)-1,4-dihydropyridin-3-yl}carboxamido)benzoic Acids Ethyl Esters

Russian Journal of General Chemistry - A series of new hybrid molecules containing fragments of anestesin and 4-(2-furyl)-1,4-dihydronicotinonitrile have been obtained starting from diketene, ethyl...     

Electrically Conductive Composites Based on Chitosan and Graphene Stabilized by Pluronic F-108

Highly concentrated dispersions of few-layer graphene stabilized by amphiphilic block copolymer Pluronic F-108 are obtained. According to transmission electron and atomic force microscopy, the thickness of the graphene particles is on average from one to ten layers and their lateral sizes vary from 150 nm to 1 μm. Using these dispersions, new chitosan-based film composites with the filler content up to 5 wt % are obtained; the electrical conductivity of these composites reaches 4.3 × 10^–1 S/cm.     

Novel approach to the synthesis of 1,3-diazapyrenes

Methods have been developed for the synthesis of 1,3-diazapyrenes based on the reactions of perimidines with ethoxymethylene-1,3-dicarbonyl compounds and also 6(7)-benzoyl(acetyl, formyl)perimidines with carbonyl compounds in PPA. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 79–82, January, 2009.     

Fast electro-optical response of a cell with a homeoplanar layer of a nematic liquid crystal

The refraction of light, i.e., the turn of an extraordinary ray in the liquid crystal layer similar to total internal reflection at an interface between two media, has been studied in a cell with the homeoplanar orientation of the director. The rise, τ_on, and decay, τ_off, times of optical responses have been obtained for various angles of incidence of light on a liquid crystal layer subjected to an electric field. The times τ_on and τ_off of optical responses for the angles of incidence much larger than the angle of total internal reflection are 1–2 ms, which is three orders of magnitude smaller than the relaxation time of an optical response in the case of normal incidence of the ray.