Influence of photocatalytic systems on the photo-cross-linking of diallyl oxydiethylene dicarbonate grafted onto cellulose

The photo-cross-linking of 18.4-20.0 μmol of diallyl oxydiethylene dicarbonate (I) grafted onto cellulose (per square contimetre of apparent cellulose surface) was examined kinetically at 30±2 °C, on exposure to an incident polychromatic radiation flux of (2.05±0.08) × 10-7 einstein s-1 cm-2, in the presence of catalytic amounts (20-200 ppm) of three vanadium- (V) organometallic compounds. As with the diacrylate systems studied previously, the kinetics of photo-cross-linking of grafted I followed a multi-relaxation spectrum in terms of two parameters (width of spectrum β and mean lifetime τ). The β values (0.42±0.04) were almost the same in all experiments and were similar to that (0.44±0.02) observed for the thermal decay of double bonds of pre-irradiated I in bulk. The β parameter therefore seems to reflect the cross-linked character of the linear polymer pattern, rather than the cross-linking process, either thermal or photocatalytic. In contrast, the τ values reflect, in a very sensitive manner, the effect of the concentration and type of photocatalytic system employed. An acceleration factor of about 190 was reached with 200 ppm vanadium (synergic mixture of vanadium (V) isopropoxide and isobutoxide). Some relevant features of the photo-cross-linking mechanism are discussed in the light of the proposed kinetic model.