Photoyellowing of poly(4,4′‐diphenylolpropane isophthalate): A novel polymer photorearrangement

Abstract

Abstract The photoyellowing of 4,4′‐diphenylolpropane isophthalate (DPP‐I) was attributed to a photochemical rearrangement resulting in a polymer containing o ‐hydroxybenzophenones as part of the chain structure. Chain cleavage by photolysis was an accompanying side reaction. o ‐Hydroxybenzophenone derivatives of DPP were prepared to serve as model compounds to confirm the structure of the photorearrangement product. Additional confirmation of the mechanism was obtained by solid phase or solution photorearrangement of the model ester, DPP dibenzoate to its monohydroxybenzophenone derivative. Kinetics of the DPP‐I photorearrangement exposed to a xenon high pressure lamp and a carbon are lamp gave rates of 3.9 × 10 −2 and 3.8 × 10 −3 mole/1.‐hr., respectively. The rate of yellowing in Florida sunlight, open exposure in April, was 1.5 × 10 −2 mole/1.‐hr.