1990 Volume 47 Issue 10 Pages 763-769
Polymer films in which various photochromic compounds were embedded were prepared. Their photocoloration, photodecoloration, and dark decoloration were studied at 15K. Photocolorations and photodecolorations proceeded at 15K in all systems. No dark reaction was observed except for a few special cases. Partial dark decoloration from photo-colored metastable species of spirooxazine derivatives in poly (methyl methacrylate) were clearly observed at 15K, where ordinary thermal decoloration would never proceed, judging from the reaction kinetics in the solution. The origin of extraordinary dark reactions in polymer matrices was reduced to the strained conformations of metastable colored species in a rigid molecular environment. The specific back reactions were discussed in terms of free volumes for chemical reactions in rigid matrices.
