STABILIZATION AND MODIFICATION OF POLYCAPROAMIDE - Photochemical Reactions in Heterochain Polymers - page 34

Figure 1.12. Spectra of fluorescence of thermo-processed PCA film during 8-16 hours at the wave-
length of exciting light of 290nm(1), 350nm(2),365nm(3).
Further thermal processing leads to gradual decrease of intensity of peakλ max em =385nm
and intensity of the band λ max em =430nm after slight decrease (by 1,5 times) becomes constant
(Figure 1.12.).
During irradiation of PCA samples by light λ max em =365nm for 2-3 hours increase of peaks
intensity is being observed, but in different relations: for λ max ex =290nm - by 7 times,
λ max ex =350nm - by 10 times, λ max ex =365nm - by 20-25 times with the shift of fluorescence
bands accordingly up to λ max em =385, 408 and 428 nm.
Further irradiation leads to decrease of intensity of the first two peaks and constant value
of the peak λ max em =428nm, which shows that the system has gone into some stationary mode.
Besides, the intensity of the peak.
λ max em =428 exceeds the intensities of other peaks by many times. So we may come to a
conclusion that fluorescence at thermo and photooxidation of PCA is connected with
accumulation of one and the same compounds.
Thus, obtained data agree well with literature ones [22, 23], where it is noted that change
of PCA glow intensity takes places simultaneously with the change of C=0 groups formed
during photooxidation. Authors, classifying PCA glow as formation of compounds of
ketomide structure [24, 25] in polymer, come to the same conclusion. These data evoke
special interest to PCA fluorescence within the limits of λ max em =428-430nm, excited by the
light λ max ex =365nm.