Photochromism of 6-nitrospiropyran in oriented polyethylene

UV-VIS and IR dichroism spectra of 1′,3′,3′-trimethyl-6-nitrospiro(2H-1-benzopyran-2,2′-indoline) (6-NSP) dispersed in stretched low density poly(ethylene) (PE) films are reported. Also the kinetics of the thermally induced decay of merocyanine (Mc) form of 6-NSP was investigated in both nonoriented and oriented samples using polarized light. The analysis of experimental data reveals that decoloration processes is faster in the stretched than in the nonstretched matrix. This is opposite to the photochromic phenomena occurring in stretched rubbers when the chromophores are bound chemically to the polymer.