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Molecular organization and aggregation in Langmuir and Langmuir-Blodgett films of azo dye/liquid crystal mixtures

Inglot K., Martyński T., Bauman D.

Opto-Electronics Review

2009

Vol. 17, No. 2

120-128

A study of azo dye/liquid crystal mixtures in monolayers formed at air-water (Langmuir films) and air-solid substrate (Langmuir-Blodgett films) interfaces was performed. Three azo dyes with various molecular structure and two liquid crystal materials: 4-octyl-4'-cyanobiphenyl (8CB) and trans-4-octyl(4'-cyanophenyl)-cyclohexane (8PCH) were used. The morphology of Langmuir films was monitored by means of a Brewster angle microscope (BAM). Moreover, a surface pressure and electronic absorption spectra of the monolayer spread on the water surface of dye/liquid crystal mixtures as a function of a mean molecular area were simultaneously recorded. In addition, the absorption for Langmuir-Blodgett films deposited on quartz plates was measured. Information about intermolecular interactions in the mixtures of the nonamphiphilic dye and the liquid crystal with polar terminal group was obtained. Conclusions about the formation of self-aggregates between dye molecules have been drawn. The influence of the dye molecular structure and its concentration on aggregates' geometry was found.

Spectral and orientational properties of new group of naphthalene derivatives of bicarboxylic acid in liquid crystal 7CB

Bielejewska N., Wolarz E., Stolarski R., Bauman D.

Opto-Electronics Review

2008

Vol. 16, No. 4

367-374

The spectral and orientational properties of some dichroic fluorescent dyes (naphthalene derivatives of bicarboxylic acid) in some isotropic solvents and in an anisotropic matrix have been studied. The order parameter of the dyes in the nematogenic liquid crystal 7CB has been determined from measurements of polarized electronic absorption and fluorescence. The influence of the dye addition on the nematic-isotropic phase transition temperature of 7CB has been investigated. It was found that some of the dyes studied could be successfully utilized in guest-host liquid crystal display devices.

Cyclic Voltammetry and Electronic Absorption Spectroscopy in Investigations of the Nature of the Electrochemical reduction of Phenyldiazonium and Phenyl-bis-diazonium Cations

Koval'chuk E., Kozlovs'ka Z., Jackowska K., Roshal A., Wróblewska A., Reshetnyak O., Błażejowski J.

Polish Journal of Chemistry

2004

Vol. 78 / nr 1

139-147

The electrochemical reduction of phenyldiazonium and phenyl-bis-diazonium cations on mercury drop and platinum cathodes exhibits a multistep nature, as demonstrate the results of polarographic and cyclic voltammetry measurements. The primarily formed radicals participate in various secondary processes, as a result of which occur species absorbing UV-VIS radiation. Electronic absorption in the visible region can be ascribed to entities forming from the recombination of two azophenyl or azophenyl and phenyl radicals, originating from the one- or two-electron reduction of primarily or secondary formed cations.