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|Title:||Alternating Binaphthyl−Thiophene Copolymers: Synthesis, Spectroscopy, and Photophysics and Their Relevance to the Question of Energy Migration versus Conformational Relaxation||Authors:||Pina, J.
Melo, J. Seixas de
Burrows, H. D.
Maçanita, A. L.
|Issue Date:||10-Mar-2009||Publisher:||American Chemical Society||Citation:||Macromolecules. 42:5 (2009) 1710-1719||Abstract:||The synthesis and a comprehensive spectroscopic and photophysical study are presented of four alternating binaphthyl−oligothiophene copolymers (DP: 10−15 repeat units) in solution at room and low temperature and in the solid state (thin films). Detailed results are presented on absorption, emission, and triplet−triplet absorption spectra together with all relevant quantum yields (fluorescence, intersystem crossing, internal conversion, and singlet oxygen formation), excited-state lifetimes, and singlet and triplet energies. From these, several conclusions can be drawn. First, the main deactivation channels for the molecules in solution are the radiationless processes (S1 → S0 internal conversion and S1 → T1 intersystem crossing). Second, in the solid state the fluorescence quantum yields are smaller than those in solution. From time-resolved fluorescence decays in the picosecond time domain, three decay components are seen: a fast decay (40−60 ps) at short wavelengths, which becomes a rising component at longer wavelengths, an intermediate decay component (330−477 ps) associated with an ensemble of isolated segment-like units, which is dominant at the initial part of the emissive spectra and progressively decreases for longer emissions, and a third exponential related to the emission of the fully relaxed polymer. Together with steady-state anisotropy studies, this is discussed in terms of the possibilities of energy migration/transfer along the polymer chain and of the conformational (torsional) relaxation of the systems studied.||URI:||http://hdl.handle.net/10316/10590||ISSN:||0024-9297||DOI:||10.1021/ma802395c||Rights:||openAccess|
|Appears in Collections:||FCTUC Química - Artigos em Revistas Internacionais|
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