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Control of Photodynamic Motions of Azobenzene‐Derivative Polymers by Laser Excitation Wavelength
Author(s) -
Kim MiJeong,
Lee JaeDong,
Chun Chaemin,
Kim DongYu,
Higuchi Seiji,
Nakayama Tomonobu
Publication year - 2007
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.200700159
Subject(s) - azobenzene , photoexcitation , photoisomerization , chemistry , photochemistry , relaxation (psychology) , absorbance , polymer , excitation , derivative (finance) , isomerization , organic chemistry , physics , psychology , social psychology , financial economics , economics , catalysis , chromatography , quantum mechanics
The dynamic properties of photoinduced alignment and surface relief grating (SRG) formation as a function of excitation wavelength ( λ ex = 454, 488, 514, 532, 568, and 647 nm) are examined using five azobenzene‐derivative polymers, whose absorption spectra are tuned by substituting different electron‐withdrawing groups (CF 3 , CN, CNCl, NO 2 , (CN) 2 ). The dynamics sensitively depend on λ ex . The fastest rate of photoinduced alignment is observed when λ ex is between λ max of the trans π – π * transition and that of the cis n– π * transition. A model of trans – cis photoisomerization has been developed based on competition between photoexcitation and relaxation, in which the n– π * transition has a faster relaxation pathway than the π – π * transition. Under conditions of adequate absorbance of the trans form at λ ex , i.e., greater than ${1 \over 2}$ A max , the rate of SRG formation increases at longer λ ex .