Photostability of substituted 4-diethylaminoazobenzenes

The stability to visible light of five 4-diethylaminoazobenzenes was invest igated in different solvents under Various experimental conditions, as well as in solid crystalline form and on dyed poly(ethyleneterephthalate). Thou gh generally exhibiting relatively high photostability, all investigated dy es underwent photodegradation in acetone solution. Two different reaction p aths were recognised in this solvent, depending on the nature and position of the substituting groups on the second aromatic ring, both involving the formation and subsequent fragmentation of organic free radicals, as suggest ed by the strong inhibiting effect of molecular oxygen on the photodegradat ion rate. (C) 2001 Elsevier Science Ltd. All rights reserved.