Abstract
Investigated were three types of aromatic nitro compounds: (a) a derivative of o‐nitrophenol capable of forming an intramolecular hydrogen bond, (b) simple aromatic nitro compounds, and (c) the intramolecular charge transfer complexes, i.e., compounds incorporating in a single molecule the donor and the acceptor moieties, the latter substituted with the nitro groups. Samples of plasticized poly(vinyl chloride) were stabilized with these compounds and tested in an Atlas Weatherometer. The extent of degradation was determined by measuring the tensile strength, elongation, and the blue light reflectance before and after 270 and 500 hr of exposure. Samples without the stabilizers and samples containing 2,4‐dihydroxybenzophenone were used as standards for comparison. Little protection was provided by simple nitro compounds. The derivative of o‐nitrophenol and the donor‐acceptor compounds were either better or comparable to 2,4‐dihydroxybenzophenone in preserving the tensile strength and elongation. It appears that the protective ability of the derivative of o‐nitrophenol was associated with the hydrogen‐bonded six‐membered ring whereas the protection rendered by the donor‐acceptor compounds was determined by the extent of the contribution of the charge transfer states and the number of benzylic hydrogens capable of undergoing photochemical reactions. However, the mechanistic interpretation of the protective ability of the donor‐acceptor compounds was complicated by the color changes occurring during the exposure.