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Various azoderivative dyes were incorporated in uncolored poly(vinyl alcohol) (PVOH). One type of film was obtained by drying the layer of solution cast on glass plate. The other type was obtained by rubbing the PVOH layer before complete drying. Linear birefringence and dichroism of dyed polymer films were investigated as a function of stretching degree. An increase in the linear birefringence was found with increasing stretching degree for both uncolored and colored films. Dichroism of the PVOH films depends on the dye chemical structure and also on the stretching degree of both non-rubbed and rubbed and dyed PVOH samples. Molecular modeling was used to examine interactions occurring between PVOH and the embedded dye molecule. These stretching degree dependencies were approximated mathematically, which was used to describe the behavior of some components of interference filters. KEYWORDS blends, dyes/pigments, films, molecular modeling, optics, 1 | INTRODUCTION Dye-containing polymers present both theoretical and practical uses in the development of new products with increased performance. [1] Depending on the properties of the incorporated dye molecules [...]

The electronic absorption spectral characteristics of cycloimmonium ylids with a zwitterionic structure have been analyzed in forty-three solvents with different hydrogen bonding abilities. The two ylids lack fluorescence emission but are very dynamic in electronic absorption spectra. Using the maximum of the ICT band, the goal was to establish an accurate relationship between the shift of the ICT visible band and the solvent parameters and to estimate two of the descriptors of the first (the) excited state: the dipole moment and the polarizability. Two procedures were involved: the variational method and the relationships of the Abe model. The results indicate that the excited state dipole moment of the two methylids decreases in the absorption process in comparison with the ground state. The introduction of a correction term in the Abe model that neglects the intermolecular H-bonding interactions leads to a more accurate determination of the two descriptors. The strong solvatochromic response of both ylids has been further applied in distinguishing the solvents as a function of their specific parameters. Principal component analysis was applied to five selected properties, including the maximum of the charge transfer band. The results were further applied to discriminate several binary solvent mixtures. [ABSTRACT FROM AUTHOR]

Fluorescein sodium is a very important compound for a wide spectrum of applications, from which medical applications prevail. Despite this, there are very few studies in the literature related to the structure and fundamental properties of fluorescein sodium and its solutions, with most of the studies dealing with fluorescein. The purpose of the present article is to determine some parameters of the fluorescein sodium molecule approaching the quantum-mechanical modeling and experimental solvatochromism in both binary and ternary solutions. For data analysis, several theoretical models were applied. The results highlight the intermolecular interactions involved in the spectral shift of the electronic absorption band of fluorescein sodium when dissolved in different solvents or binary solvents and allowed the estimation of the difference between the interaction energy in molecular pairs of the type of fluorescein sodium − solvent 1 and fluorescein sodium − solvent 2. By applying a variational method, the dipole moment in the first excited state of the fluorescein sodium molecule and the angle between the dipole moments in the ground and excited states, respectively, were estimated. These results are useful for a better understanding of the behavior of fluorescein sodium when dissolved in different solvents or combinations of solvents, to develop new practical applications. [ABSTRACT FROM AUTHOR]

Investigation of chiroptical polymers in the solution phase is paramount for designing supramolecular architectures for photonic or biomedical devices. This work is devoted to the case study of poly(propylene oxide) (PPO) optical activity in several solvents: benzonitrile, carbon disulfide, chloroform, ethyl acetate, and p-dioxane. To attain information on the interactions in these systems, rheological testing was undertaken, showing distinct variations of the rheological parameters as a function of the solvent type. These aspects are also reflected in the refractive index dispersive behavior, from which linear and non-linear optical properties are extracted. To determine the circular birefringence and specific rotation of the PPO solutions, the alternative method of the channeled spectra was employed. The spectral data were correlated with the molecular modeling of the PPO structural unit in the selected solvents. Density functional theory (DFT) computational data indicated that the torsional potential energy—related to the O1-C2-C3-O4 dihedral angle from the polymer repeating unit—was hindered in solvation environments characterized by high polarity and the ability to interact via hydrogen bonding. This was in agreement with the optical characterization of the samples, which indicated a lower circular birefringence and specific rotation for the solutions of PPO in ethyl acetate and p-dioxane. Also, the shape of optical rotatory dispersion curves was slightly modified for PPO in these solvents compared with the other ones. [ABSTRACT FROM AUTHOR]

This article contains a comparative spectral analysis corroborated with the quantum mechanical computations of four cycloimmonium ylids. The spectral shift of the visible electronic absorption band of the studied molecules in 20 solvents with different empirical parameters is expressed by linear multi-parametric dependences that emphasize the intramolecular charge transfer (ICT) process. The nature of molecular interactions and their contribution to the spectral shift of the visible ICT band of solutes are also established in this manuscript. The results of the statistical analysis are used to estimate the cycloimmonium ylids' excited dipole moment by the variational method, using the hypothesis of McRae. The importance of the structure of both the heterocycle and carbanion substituents to the stability and reactivity of the studied cycloimmonium ylids is underlined by the quantum mechanical computations of the molecular descriptors. [ABSTRACT FROM AUTHOR]

Optically birefringent polymers have found utility in numerous applications, especially in liquid crystal displays. This work is focused on inducing molecular ordering in polyvinyl alcohol films in different conditions. The samples were modified by new mixed approaches: drawing, rubbing before drying, rubbing before drying followed by drawing, and combined rubbing, drawing and then parallel scratching. The level of chain alignment in the samples was quantified by birefringence measurements using several experimental techniques, namely interferometry, polarization ellipse approach, channeled spectra and polarized light refractometry. The produced anisotropy was correlated with the sample morphology examined via optical microscopy under crossed polarizers. Optical retardation was found to be larger as the generated birefringence of mechanically deformed polyvinyl alcohol foils was higher. It was found the new proposed approach of ordering polymer sample by combined rubbing, drawing and then scratching is most suitable as retardation layer for compensating light leakage in display devices. [ABSTRACT FROM AUTHOR]

Gallic acid (GA) molecule was studied by quantum-chemical and experimental approaches since it is a remarkable antioxidant product that could be used to improve the biocompatibility of magnetite nanoparticles in colloidal suspension. Computational modeling has evidenced significant dipolar character as well as good reactivity and stability. The preparation of magnetite nanoparticles capped with GA has resulted in stable colloidal suspension as revealed by Transmission Electron Microscopy investigation. A solvatochromic study was carried out on GA in binary and ternary solutions, evidencing the coexistence of the main types of universal solute–solvent interactions. Based on the spectral behavior in protic and polar solvents the dipole moment vector in the excited state was found. [ABSTRACT FROM AUTHOR]

The proposed method employs the recorded channeled spectrum of an optical active medium (crystal or liquid solution) placed between two crossed polarizers. The method of channeled spectrum, previously validated for quartz samples, is used to determine the optical rotatory dispersion of hydroxypropyl cellulose solutions (HPC) in water. Both the specific rotation and dispersion parameter depend on the wavelengths of the maxima and minima from the channeled spectrum and on the thickness of the optical active sample. The circular birefringence and its dispersion determined for HPC solutions in water of concentrations 30% and 45% were estimated with a precision of about 0.5%. The rotatory birefringence of HPC in water at 45% is (119.75-57.60)[10.sup.-6] and the specific rotation determined in the visible range for these solutions has values between 4782 and 1402 degrees/dm, in agreement with the literature. The specific rotation (angle) of HPC solutions is independent of the polymer concentration and represents a dispersive parameter which decreases with the light wavelength., INTRODUCTION The nature's ability to produce numerous chiral, optically active compounds, such as nucleic acids, proteins, and polysaccharides, inspired the scientists to develop new synthetic materials with properties as effective [...]