STABILIZATION AND MODIFICATION OF POLYCAPROAMIDE - Photochemical Reactions in Heterochain Polymers - page 36

Similar results were obtained during investigation of spectra of excitation, absorption and
luminescence of films and solutions of dyed and undyed PCA samples, and also on using
other dyes- stabilizers of this series.
Absence of dyed PCA in fluorescence spectrum, containing 1% (1,8·10 -2 mole / kg ) of the
dye from polymer mass of the peak λ max em =425nm (fluorescence peak of initial PCA), may be
explained by large fluorescence intensity of the dye itself. Since it is impossible to judge
suppression of PCA fluorescence at such relatively high dye concentration, measurements of
fluorescence at lower concentrations have been carried out. PCA films with 10-20 μm of
thickness, containing 7·10 -5 -1,5·10 -2 mole / kg of the dye were obtained for these measurements.
There were read spectra of fluorescence of films (initial and thermoprocessed) and polymer
solutions in the mixture of formic (85%) and tri fluoro-acetic acids in relation 1:1.
During check experiments it has been shown that the solution being used does not
influence spectral characteristics of tested samples in investigated region of wave-lengths.
Spectra of PCA films fluorescence with different content of XLY compounds are given
in Figure 1. 14. As it is seen from the figure intensity of the peak λ max em =425nm decreases
with the rise of dye concentration, but at dye concentration 0,7·10 -3 mole / kg spectrum character
changes - there takes place the shift of the peak of PCA fluorescence into the region with
longer waves (470-490nm). Averaging of luminescence peak of initial PCA and its dyed
analog takes place. Shift of the peak into the region with longer waves may be explained not
only by additive absorption, but by the beginning of realization of energy transfer from PCA
to the dye and its simultaneous deactivation by luminescence of the dye itself.
Figure1.14. Luminescence spectra of PCA films: initial (I) and dyed by XLY compound (2-9).
Conservation of XLY (mole/kg); 0,7·10-4 (2); 1,5·10-4 (3); 3,5·10-4 (4); 0,7·10-3 (5); 1,5·10-3 (6);
3,5·10-3 (7); 0,7·10-2 (8); 1,5·10-2 (9).