Effect of mechanical treatments on orientation behavior and spectral properties of azoderivative dyes incorporated in poly(vinyl alcohol) films

Abstract

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.

Birefringence of Thin Uniaxial Polymer Films Estimated Using the Light Polarization Ellipse

“…The rubbing action add supplemental small birefringence to the intrinsic one of the unstretched foil. The same conclusion resulted also from the experiments organized in [14].…”

“…Each experimental value was measured ten times and the averaged values are presented in the tables. In Table 1, the results of measurements for a PVA foil rubbed as it was described in [14] are noted, showing the intrinsic birefringence of the polymer foils. In this table, the angles α and θ and the flux densities measured along the semi axes of the rotated ellipse are noted, for a given PVA polymer foil.…”

“…The last two materials have the advantage that their birefringence can be modified by external field of forces [1,2]. There are some methods for determining both linear [3][4][5][6][7][8] and circular [9][10][11][12][13] birefringence of the anisotropic layers, based on the compensation of the optical path length [3][4][5][6][7][8][9][10][11][12][13][14][15] or interferometric means [3,8,10]. For thick anisotropic layers the method based on channeled spectra [3,10,12] is usually applied.…”

“…This method is very precise and allows measurements for all components of light in a single experiment. The birefringence can be determined by using compensators (e.g., Babinet compensator used in our laboratory [4][5][6][7][8]14,15]), but the experiment asks for monochromatic radiations for which the compensatory device must be standardized.…”

Review on Optical Methods Used to Characterize the Linear Birefringence of Polymer Materials for Various Applications

“…Introduction of azo-derivatives in PVA films under stretching also created optical birefringence [ 68 ], as examined with the Babinet compensator instrument. In this case, the films suffered a similar mechanical treatment (stretched or rubbed and stretched).…”