No abstract

To establish correlations between the optical and morphological properties of anisotropic polyvinyl alcohol (PVA) foils containing Congo red (CR) dye in various concentrations, characteristics such as degree of crystallinity, dichroic ratio, order parameter, birefringence, surface morphology, and three-dimensional texture parameters were estimated before and after stretching. An increase in morphological and optical anisotropy with the degree of stretching has been evidenced for both pure and CRcontaining PVA foils, this behavior being facilitated by the presence of the dye. The study of these properties lays the foundation for understanding the circumstances in which PVA foils containing CR can be used as polarizing filters.

No abstract

Linear correlation between the 𝐸max (kcal/mol) of the visible electronic absorption band of four pyridazinium ylids and the empirical polarities 𝑍 (kcal/mol) defined by Kosower are established, proving the intramolecular charge transfer nature of this band. The slopes of the lines are smaller for the carbanion monosubstituted ylids, compared with those of the carbanion disubstituted ylids. This fact emphasizes the prevalence of the dipolar interactions in ylid solutions.The blue shifts recorded in the protic solvents suggest the hydrogen bond formation between the -OH of these solvents and the ylid carbanion.A linear dependence exists between the values of 𝐸max (kcal/mol) recorded for two studied ylids. This fact demonstrates that the solvents can be arranged on the empirical scale describing their action on similar chemical compounds, in which electronic transitions of the same nature take place. K e y w o r d s: electronic absorption spectra, ylids, 1-ethyl-4-carbomethoxy-pyridinium iodide.

The electronic absorption spectra of five polycyclic polyenes were recorded in non-polar solvents in order to determine their polarizability in excited states from the strength of the dispersive interactions in their diluted solutions. The bathochromic shifts of p-p* vibronic bands prove the increase of the molecular polarizabilty in the photon absorption process. Some molecular parameters of the analyzed polyenes in their ground state were computed by using the programs from Spartan�14.