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Title: Polyene photoisomerization rates: Are they distinct in aqueous block copolymer micellar solutions and gels?

Abstract

Photoisomerization of 3,3{sup '}-diethyloxadicarbocyanine iodide (DODCI) has been investigated in water, 5% and 30% aqueous triblock copolymer, poly(ethylene oxide){sub 20}-poly(propylene oxide){sub 70}-poly(ethylene oxide){sub 20} (P123) by measuring the fluorescence quantum yields and lifetimes in the temperature range 293-318 K. Reports available in literature indicate that 5% aqueous P123 exists as micellar solution, whereas 30% aqueous P123 forms gel due to micelle-micelle entanglement. This study has been undertaken to find out how the polyene photoisomerization rates are influenced in the sol and gel phases. It has been observed that 60%-70% of DODCI is located in the palisade layer of the micelles in the sol as well as gel phases and the photoisomerization rate of this component is identical in both the phases at a particular temperature. The remainder of the probe is located in the interfacial region and isomerization rates of this fraction are slower by a factor of 1.4-1.1 in the gel phase compared with the micellar solution. The retardation of the isomerization rate in the gel phase has been explained on the basis of enhancement in the friction experienced by the probe due to micelle-micelle entanglement at the interface. Compared to the isomerization rates in water, the rates ofmore » photoisomerization of DODCI located in the palisade layer, interfacial region of micellar solution, and interfacial region of the micelles in the gel phase are slower by factors of 3.5, 1.5-1.9, and 2, respectively. The outcome of this study validates the point that in organized media photoisomerization rates are sensitive to the localized friction, which is not uniform unlike in a homogeneous solution.« less

Authors:
; ;  [1]
  1. Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)
Publication Date:
OSTI Identifier:
20783222
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 124; Journal Issue: 5; Other Information: DOI: 10.1063/1.2162877; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; COPOLYMERS; FLUORESCENCE; GELS; ISOMERIZATION; ORGANIC IODINE COMPOUNDS; PHOTOCHEMISTRY; POLYENES; REACTION KINETICS; SOLUTIONS; TEMPERATURE RANGE 0273-0400 K; WATER

Citation Formats

Mali, K.S., Dutt, G.B., and Mukherjee, T. Polyene photoisomerization rates: Are they distinct in aqueous block copolymer micellar solutions and gels?. United States: N. p., 2006. Web. doi:10.1063/1.2162877.
Mali, K.S., Dutt, G.B., & Mukherjee, T. Polyene photoisomerization rates: Are they distinct in aqueous block copolymer micellar solutions and gels?. United States. doi:10.1063/1.2162877.
Mali, K.S., Dutt, G.B., and Mukherjee, T. Tue . "Polyene photoisomerization rates: Are they distinct in aqueous block copolymer micellar solutions and gels?". United States. doi:10.1063/1.2162877.
@article{osti_20783222,
title = {Polyene photoisomerization rates: Are they distinct in aqueous block copolymer micellar solutions and gels?},
author = {Mali, K.S. and Dutt, G.B. and Mukherjee, T.},
abstractNote = {Photoisomerization of 3,3{sup '}-diethyloxadicarbocyanine iodide (DODCI) has been investigated in water, 5% and 30% aqueous triblock copolymer, poly(ethylene oxide){sub 20}-poly(propylene oxide){sub 70}-poly(ethylene oxide){sub 20} (P123) by measuring the fluorescence quantum yields and lifetimes in the temperature range 293-318 K. Reports available in literature indicate that 5% aqueous P123 exists as micellar solution, whereas 30% aqueous P123 forms gel due to micelle-micelle entanglement. This study has been undertaken to find out how the polyene photoisomerization rates are influenced in the sol and gel phases. It has been observed that 60%-70% of DODCI is located in the palisade layer of the micelles in the sol as well as gel phases and the photoisomerization rate of this component is identical in both the phases at a particular temperature. The remainder of the probe is located in the interfacial region and isomerization rates of this fraction are slower by a factor of 1.4-1.1 in the gel phase compared with the micellar solution. The retardation of the isomerization rate in the gel phase has been explained on the basis of enhancement in the friction experienced by the probe due to micelle-micelle entanglement at the interface. Compared to the isomerization rates in water, the rates of photoisomerization of DODCI located in the palisade layer, interfacial region of micellar solution, and interfacial region of the micelles in the gel phase are slower by factors of 3.5, 1.5-1.9, and 2, respectively. The outcome of this study validates the point that in organized media photoisomerization rates are sensitive to the localized friction, which is not uniform unlike in a homogeneous solution.},
doi = {10.1063/1.2162877},
journal = {Journal of Chemical Physics},
number = 5,
volume = 124,
place = {United States},
year = {Tue Feb 07 00:00:00 EST 2006},
month = {Tue Feb 07 00:00:00 EST 2006}
}