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Triplet-Triplet Energy Transfer in Photocrosslinkable Dendrimers

Published online by Cambridge University Press:  01 February 2011

Seiichi Furumi
Affiliation:
Nanotechnology group, Kansai Advanced Research Center, Communications Research Laboratory
Akira Otomo
Affiliation:
Nanotechnology group, Kansai Advanced Research Center, Communications Research Laboratory
Shiyoshi Yokoyama
Affiliation:
Nanotechnology group, Kansai Advanced Research Center, Communications Research Laboratory PRESTO, Japan Science and Technology Corporation (JST), 588-2 Iwaoka, Nishi-ku, Kobe 651-2492, JAPAN.
Shinro Mashiko
Affiliation:
Nanotechnology group, Kansai Advanced Research Center, Communications Research Laboratory
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Abstract

This report describes the synthesis of photocrosslinkable dendrimers with peripheral cinnamamide residues, which exhibit both photoisomerization and photodimerization, and their photochemical and photophysical properties in dilute solutions and polymer matrices. Photoirradiation with 313 nm gave rise to monotonous decrease in the absorbance of trans-cinnamamide at 270 nm as a result of the photochemical reactions of the cinnamamide residues. Spectral analysis revealed the changes in the photoproduct distribution of trans- and cis-photoisomerized and photodimerized cinnamamide groups to be a function of the exposure energy. In dilute solutions, the first-generation dendrimer displayed preferential formation of cis-isomer of the cinnamamide, whereas the photodimerization took place more favorably for the third- and fifth-generation dendrimers. The photochemical behavior was strongly dependent on the dendrimer generation rather than the concentration, probably due to the extent of steric crowding among the cinnamamide residues at terminal positions. Furthermore, the third- and fifth-generation dendrimers showed capturability of a benzophenone derivative into the macromolecules and triplet-triplet energy transfer in the photocrosslinkable dendrimers. This novel phenomenon of the triplet-triplet energy transfer in the dendritic cavities suggests potential applicability to design and fabricate novel optical and electrical molecular devices.

Type
Research Article
Copyright
Copyright © Materials Research Society 2002

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