{'fraction_non_alphanumeric': 0.023748064016520392, 'fraction_numerical': 0.00980898296334538, 'mean_word_length': 4.926605504587156, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Kinetics of isomerization of spiropyran and molecular dynamics in emulsion layers : Effect of dehydration of gelatin gel

The kinetics of dark isomerization of the merocyanine form of 1,3,3-trimethyl-6'-nitroindoline-2-spiro-2'-benzopyran (I) in emulsions with water-gelatin gel as a dispersion medium were studied by flash photolysis. Esters with various viscosities were used as organic phases, and anionic, cationic, and nonionic surfactants were used as emulsifiers. The kinetics of isomerization is described by a single exponent and does not depend on concentration of I in the range 5 x 10 -4 - 5 x 10 -2 M. The rate constants for isomerization of I (k j ) decrease with an increase in viscosity of organic phase but do not change on going from homogeneous solutions to emulsions in gelatin gel. However, the values of k i decrease by 1.5 - 2 times upon dehydration of the gel, the magnitude of the effect being independent of the nature of surfactant. Using EPR spectroscopy with hydrophobic and two surface-active spin probes localizing at various depth from the interface, it was shown that the structure-dependent dynamic parameters of microvolumes of organic phase of emulsions are not changed upon dehydration but the properties of their interfaces are significantly altered: microviscosity increased and polarity of probe environment decreased. The conclusion was drawn that in emulsions with water-gelatin gel as a dispersion medium isomerization of I occurs inside the droplets of organic phase, whereas upon gel dehydration isomerization takes place in their surface layer, where the zwitterionic form of I is predominantly localized, apparently due to sorption on gelatin molecules. Upon gel dehydration, the depth of gelatin penetration into organic phase does not exceed 20 A, although it is larger than the length of surfactant molecules, because the values of k i in gel are independent of the nature of surfactant.