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Insight into the Role of Oxidation in the Thermally Induced Green Band in Fluorene‐Based Systems
Author(s) -
Grisorio R.,
Suranna G. P.,
Mastrorilli P.,
Nobile C. F.
Publication year - 2007
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200600083
Subject(s) - polyfluorene , fluorene , materials science , fluorenone , photoluminescence , incandescence , photochemistry , cyclohexane , green light , intersystem crossing , annealing (glass) , chemical engineering , degradation (telecommunications) , polymer , copolymer , composite material , organic chemistry , optoelectronics , soot , excited state , blue light , telecommunications , physics , computer science , nuclear physics , singlet state , engineering , combustion , chemistry
The causes of the spectral instability of poly[9,9‐dioctylfluoren‐2,7‐diyl‐co‐2′,7′‐spiro(cyclohexane‐1,9′‐fluorene)] during thermal annealing in air, which leads to a green photoluminescence (PL) emission band, are investigated. The I green / I blue ratio evolution ( I = intensity) is found to be independent of the amount of monoalkylfluorene defects, despite the fact that their presence might be regarded as a trigger for the radical process leading to polymer degradation in the presence of a trace amount of metal catalyst. Furthermore, the absence of a correlation between the degree of oxidation of the material and the I green / I blue ratio indicates that the spatial disposition of fluorenones formed during the thermal degradation of the material, rather than their amount, is to be strictly related to the I green / I blue ratio. The evidenced formation of fluorenone agglomerates, which could be considered the cause for the consistent increase in the I green / I blue ratio during a thermal oxidation of a polyfluorene, confirms that the radical mechanism can also involve dialkylfluorene systems. Finally, the higher resistance to thermal degradation shown by spirocyclohexane fluorene units with respect to dioctylfluorene ones allows the synthesis of new, spectrally stable, fluorene‐based copolymers.