STABILIZATION AND MODIFICATION OF POLYCAPROAMIDE - Photochemical Reactions in Heterochain Polymers - page 33

1.6. S PECTRAL - L UMINESCENT I NVESTIGATIONS OF PCA,
C ONTAINING A DDITIVES OF B IS -A ROILENBENZIMIDAZOLE
1.6.1. Spectral - Luminescent Properties of PCA
Before considering the action of derivatives of bis-(1,8-benzoilen-1,2-benzimidazole) and
bis-(1,8-naphthoilen-1,2-benzimidazole), as possible suppressors of polymer exited states, it
was necessary to study fluorescence of initial PCA.
Spectra of fluorescence of unirradiated and thermo-unprocessed PCA film are shown in
Figure 1.11. These spectra show that maximums of fluorescence wave-lengths (λ max em ):375,
425 and 430 nm correspond to different wave-lengths of exciting light (290nm, 350nm,
365nm), moreover intensity of the band 340nm is twice higher than others. All this speaks
about the presence of several glow centres in PCA which may be classified as impurities
[133] and products of polymer oxidation [20], being formed during polymerization.
Fluorescence spectra of fibres differ from fluorescence spectra of films by small shift (3-
5nm) into the region with more long waves. This difference may be explained by distinction
in physical structure and degree of macromolecules orientation during samples production.
Fibres have greater crystallinity in comparison with the film, which is proved by X-ray
diffraction analyses.
Effect of thermal processing of PCA on its luminescent properties has been considered.
Thermal processing for 4-8 hours leads to the increase of peaks intensity λ max em =375 and
425nm (by 5-7 times) with simultaneous shift of the band λ max em =375nm up to 385nm into
long-wave region and the band λ max em =425nm into short-wave region 410nm, at the time
when intensity of the peak λ max em =430nm increases almost by 30 times.
Figure 1.11. Fluorescence spectra of unirradiated and thermo-unprocessed PCA film at the exciting
light wave-length of 290nm(1), 350nm(2),365nm(3).