Studies of energy transfer and molecular mobility in polymer photochemistry

Photochemical Reactions of Surfactant Molecules in Condensed Monolayer Assemblies—Environmental Control and Modification of Reactivity

“…From measurements of the absorption spectrum with polarized light, in analogy to results obtained by Kuhn et. al.L51 with structurally related cyanine dyes, we conclude that the chromophore of (1) lies at or near the hydrophilic interface parallel to the surface in films and assemblies. On irradiation of films or assemblies containing cis-(I) a rapid and irreversible conversion to trans-(l) is observed.…”

“…The reaction has been examined using assemblies having different architecture. It has been found that a photoreduction takes place both in multilayer assemblies of porphyrins (6) or (7) as well as in systems containing only a single outer hydrophilic or hydrophobic layer; however, reaction is considerably more rapid when assemblies containing only [1][2][3][4] outer monolayers of palladiumporphyrin are irradiatedl7'I. The fact that both porphyrins react at comparable rates is interesting since porphyrin (6) is believed to lie in a relatively more hydrophobic environment than (7), which lies at the hydrophilic interface.…”

Degradation of acrylonitrile-butadiene-styrene and polycarbonate by UV irradiation

“…Even I 3 , which was showing a steady decrease till this point, is constant from here onwards. Most of the aryl esters and carbonates on photolysis undergo a rearrangement called photo-fries rearrangement [10,40,41]. If PC undergoes photo-fries rearrangement upon UV irradiation it will result in the production of photostabilisers, phenyl salicylate (I) and 2,2 H -dihydroxybenzophenone (II) [16,42].…”

“…The presence of a substituent group in a chromophore can shift the absorption band to either longer wavelength (bathochromic shift) or to shorter wavelength (hypsochromic shift) [9]. Intermolecular energy exchange occurs by transfer of energy from small chromophore molecules to those on a polymer chains [10]. The energy transfer can also occur by energy hopping from group to group along a polymer chain, exciton bond migration along the backbone of the polymer chains and hopping across loops in the case of folded polymer chains [10].…”

“…Intermolecular energy exchange occurs by transfer of energy from small chromophore molecules to those on a polymer chains [10]. The energy transfer can also occur by energy hopping from group to group along a polymer chain, exciton bond migration along the backbone of the polymer chains and hopping across loops in the case of folded polymer chains [10].…”