CHLOROPHYLLS IN POLYMERS. II. PHEOPHYTINaIN POLYMERS and THE INFLUENCE OF STRETCHING ON THE STATE OF CHLOROPHYLLS IN ANHYDROUS POLYMER FILMS

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Abstract
Abstract—Inthe first part of this study the spectral properties of pheophytinain rigid, unstretched anhydrous polyvinyl alcohol and nitrocellulose films have been studied in order to establish the influence of the central magnesium atom on the state of chlorophylls in polymer systems. The absorption, fluorescence, excitation spectra and fluorescence intensity decays in the polymer films and in the solutions from which they are cast are reported. It is shown that pheophytinaaggregate formation is influenced by the nature of the polymer system. An aggregate of pheophytinais found in polyvinyl alcohol films over a wide concentration range. On the other hand, pheophytinaexists in the monomeric form in unstretched nitrocellulose films at concentrations below 6 × 10‐6mol/g.In the second part of this work, the influence of stretching of the films on the state and distribution of embedded chlorophyll pigments, is described. Here we show that the chlorophyllamolecules are found to undertake a heterogenous distribution in polyvinylalcohol matrices, since stretching partially disrupts the pocket‐like structures present in unstretched films. In contrast, chlorophyllaand pheophytinamolecules can be embedded in a monomeric state in nitrocellulose matrices and moreover they remain homogeneously distributed upon stretching. The chlorophyll/nitrocellulose system is concluded to be a useful model system for studies of donor‐donor energy transfer processes.

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