Document Detail

Thermochromism of a poly(phenylene vinylene): untangling the roles of polymer aggregate and chain conformation.
MedLine Citation:
PMID:  19928846     Owner:  NLM     Status:  PubMed-not-MEDLINE    
We report reversible thermochromism of a conjugated polymer, poly{2,5-bis[3-(N,N-diethylamino)-1-oxapropyl]-1,4-phenylenevinylene} (DAO-PPV), in diluted solutions of toluene and 1,2-dichlorobenzene. By means of temperature- and solvent-dependent steady-state spectroscopy, picosecond time-resolved photoluminescence spectroscopy, and dynamic light scattering, we provide new insights into the role of polymer aggregates in defining the thermochromic behavior of PPVs. We find DAO-PPV to exhibit a low temperature state with vibronically structured red visible absorption and emission spectra. Structurally, this low temperature state is a densely packed and disordered polymer aggregate, which contains a fraction of well-ordered, packed polymer chains. These ordered regions serve as low energy trap sites for the more disordered regions in the aggregate, thus regulating the final emission of the aggregate and imposing a vibronically resolved emission spectrum, which is usually associated with emission from one or a few chromophores. The high temperature state of DAO-PPV is a loose aggregate, with structureless absorption and emission spectra in the green visible range. Structurally, the loose aggregate is a well-solvated aggregate retaining the physical dimension of the dense aggregate but for which interchain interactions are diminished with the increase of temperature. As a result, the spectroscopic behavior of the loose aggregate is very similar if not identical to that of the single polymer chain. Increased solubility untangles polymer aggregates into single, dispersed, polymer chains, as we demonstrate here for DAO-PPV in 1,2-dichlorobenzene and at high temperature.
Chun-Chih Wang; Yuan Gao; Andrew P Shreve; Chang Zhong; Leeyih Wang; Kumara Mudalige; Hsing-Lin Wang; Mircea Cotlet
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  The journal of physical chemistry. B     Volume:  113     ISSN:  1520-5207     ISO Abbreviation:  J Phys Chem B     Publication Date:  2009 Dec 
Date Detail:
Created Date:  2009-12-16     Completed Date:  2010-02-18     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101157530     Medline TA:  J Phys Chem B     Country:  United States    
Other Details:
Languages:  eng     Pagination:  16110-7     Citation Subset:  -    
Physical Chemistry and Applied Spectroscopy, Chemistry Division, Mail Stop J567, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
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