The influence of amphiphilic polymers on the photocatalytic activity of water-soluble porphyrin photosensitizers

The influence of amphiphilic polymers polyvinylpyrrolidone, poly(ethylene oxide), poly(vinyl alcohol), and pluronic F127 (propylene oxide-ethylene oxide triblock copolymer) on the catalytic activity of a number of water-soluble metal-free porphyrin photosensitizers was studied in the reaction of tryptophan photooxidation in aqueous solution. The introduction of the specified polymers was found to enhance the activity of carbon-substituted tetrafluorophenylporpyrin, photoditazine, and dimegin. It was ascertained that introduction of polyvinylpyrrolidone had the strongest effect on the increase in the photooxidation process rate; the change in the activity of porphyrins was 30–70%. The introduction of poly(ethylene oxide), poly(vinyl alcohol), and pluronic F127 was shown to enhance the rate of the process by 10–40%. It was concluded that this polymer effect was connected with the dissociation of aggregates, in which form porphyrin molecules were present in aqueous solutions, as indicated by an increase in fluorescence intensity of porphyrins. The introduction of polymers resulted in a bathochromic shift of the fluorescence bands for all porphyrins, which accounted for the formation of complexes of porphyrin sensitizers with the polymers.