TEMPERATURE-INDUCED PHASE-TRANSITION OF PYRENE-LABELED (HYDROXYPROPYL)CELLULOSE IN WATER - PICOSECOND FLUORESCENCE STUDIES

被引：76

作者：

WINNIK, FM ^{[1
]}

TAMAI, N ^{[1
]}

YONEZAWA, J ^{[1
]}

NISHIMURA, Y ^{[1
]}

YAMAZAKI, I ^{[1
]}

机构：

[1] HOKKAIDO UNIV,FAC ENGN,SAPPORO,HOKKAIDO 060,JAPAN

来源：

JOURNAL OF PHYSICAL CHEMISTRY | 1992年 / 96卷 / 04期

关键词：

D O I：

10.1021/j100183a079

中图分类号：

O64 [物理化学（理论化学）、化学物理学];

学科分类号：

070304 ; 081704 ;

摘要：

Picosecond time-resolved fluorescence experiments were performed with solutions in water of pyrene-labeled (hydroxypropyl)celluloses with three different levels of pyrene incorporation (1 pyrene per 26, 56, and 438 glucopyranose units), but identical molecular weights. These solutions exhibit a lower critical solution temperature (LCST) at ca 42-degrees-C. The kinetics of pyrene excimer formation for solutions of these polymers (26.4 ppm) were monitored below and above the LCST. At 10 and 25-degrees-C, the time-resolved spectra show two types of excimer emissions with maxima (1) at 420 nm (0-7 ns time scale), assigned to a one-center-type excimer similar to that observed in pyrene single crystals and (2) at 470 nm (after 50 ns), assigned to a sandwich-type excimer. Both excimers originate from preformed ground-state pyrene aggregates. By contrast, at 45-degrees-C only one excimer emission was observed with a maximum at 470 nm. It originates predominantly from the dynamic encounter of excited and ground-state pyrenes.

引用

页码：1967 / 1972

页数：6

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[2]

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