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Influence of pressure on cyclization of a polystyrene chain. Time-resolved fluorescence measurements

✍ Scribed by A.T. Reis e Sousa; E.M.S. Castanheira; J.M.G. Martinho; S. Saghbini; F. Baros; J.C. André; Mitchell A. Winnik

Publisher
Elsevier Science
Year
1993
Tongue
English
Weight
368 KB
Volume
213
Category
Article
ISSN
0009-2614

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✦ Synopsis

The cyclization of a polystyrene chain (M,,=4500, .&4,/M.= 1.08), both ends labelled with I -pyrenyl groups, was studied in toluene and methylcyclohexane from 1 to 3500 bar. The major effect of pressure on the cyclization rate constant comes from its effect upon the viscosity. Nevertheless, for a full understanding of the results, changes in the quality of the solvent for the polymer should occur in methylcyclohexane (a poor solvent), but not in toluene (a good solvent). The rate of the excimer dissociation process increases with pressure, this being attributed to a decrease of the excimer binding energy, owing to the diminution of the distance between pyrenes in an excimer sandwich conformation.

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