화학공학소재연구정보센터
홈 로그인 로그아웃 연락처 사이트맵
Macromolecular Research, Vol.16, No.3, 224-230, April, 2008
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Solvent-Induced Photoemissions of High-Energy Chromophores of Conjugated Polymer MEH-PPV: Role of Conformational Disorder
Rakchart Traiphol1, 2, †, and Nipaphat Charoenthai1
  • 1Laboratory of Advanced Polymers and Nanomaterials, Department of Chemistry, Faculty of Science, Naresuan University, Phitsanulok 65000, Thailand
  • 2NANOTEC Center of Excellence at Mahidol University, Center of Nanoscience and Nanotechnology, Mahidol University, Rama 6 Road, Ratchathewi, Bangkok 10400, Thailand
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This study examined the photoemission behaviors of isolated chains of poly[2-methoxy, 5-(2'-ethylhexyloxy)-1,4-phenylenevinylene](MEH-PPV) dispersed in various solvents including dichloromethane, chloroform and tetrahydrofuran(THF). A change in polymer-solvent interactions in these solutions caused the MEH-PPV chains to adopt different local conformations, which in turn affected their radiative de-excitation pathways. For the polymer in dichloromethane and chloroform, in which the conjugated chains are relatively extended, photoemission occurs mostly at the long chromophores with lowest HOMO-LUMO energy gap. Their emission spectra showed a main peak at ~560 nm. Dual photoemission of high- and low-energy chromophores was observed when the conjugated chains were forced to partially collapse in a poor solvent THF. Novel high-energy peaks and a typical low-energy peak were detected at ~414 nm and ~554 nm, respectively. The observation of the high-energy peaks indicates significant suppression of the intrachain energy transfer process, which was attributed to the increase in conformational disorder in the partially collapsed coils. An analysis of the excitation spectra suggests that the high-energy peaks belong to short chromophores constituting of one or two repeat units. This study systematically investigated the effects of polymer concentration, temperature and single bond defects along the backbone on the photoemission of the high-energy chromophores.
Keywords:solvent effects;conjugation length;photophysics;fluorescence spectroscopy
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