Variable Band Gap Poly(arylene ethynylene) Conjugated Polyelectrolytes

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• 作者：Xiaoyong Zhao ; Mauricio R. Pinto ; Lindsay M. Hardison ; Jeremiah Mwaura ; Juergen Mü ; ller ; Hui Jiang ; David Witker ; Valeria D. Kleiman ; John R. Reynolds ; Kirk S. Schanze
• 刊名：Macromolecules
• 出版年：2006
• 出版时间：September 19, 2006
• 年：2006
• 卷：39
• 期：19
• 页码：6355 - 6366
• 全文大小：670K
• 年卷期：v.39,no.19(September 19, 2006)
• ISSN：1520-5835

文摘

A series of poly(arylene ethynylene) (PAE) conjugated polyelectrolytes (CPEs) have been preparedusing palladium-mediated (Sonogashira) coupling chemistry. The series consists of five pairs of polymers thatshare the same poly(arylene ethynylene) backbone. One member of each pair contains anionic sulfonate (R-SO₃^-) side groups, whereas the other member contains cationic bis-alkylammonium (R-N⁺-R-N⁺-R) side groups.The repeat unit structure of the poly(arylene ethynylene) backbone consists of a bis(alkoxy)phenylene-1,4-ethynylene unit alternating with a second arylene ethynylene moiety, and five different arylenes were used, Ar= 1,4-phenyl, 2,5-pyridyl (Py), 2,5-thienyl (Th), 2,5-(3,4-ethylenedioxy)thienyl (EDOT), and 1,4-benzo[2,1,3]thiodiazole (BDT). The different arylene units induce variation in the HOMO-LUMO band gap across the seriesof polymers, resulting in a series of materials that display absorption maxima at wavelengths ranging from 400to 550 nm and fluorescence maxima ranging from 440 to 600 nm. The absorption and fluorescence properties ofthe CPEs were investigated in methanol, water, and in methanol/water mixtures. The photophysical data suggestthat the CPE chains aggregate in water, but in methanol, the polymers are well solvated such that the opticalproperties are characteristic of the "molecularly dissolved" chains. Stern-Volmer (SV) fluorescence quenchingstudies were carried out using ionic naphthalene diimides as electron acceptors. The results show that thefluorescence from the CPEs was quenched with very high efficiency (amplified quenching) when the ionic diimidewas charged opposite to the charge on the CPE chain. The sensitivity of the Stern-Volmer quenching responsevaries strongly across the series of CPEs, with the most efficient quenching seen for polymers that display efficientfluorescence when they are aggregated. The relationship between CPE side chain structure, band gap, fluorescencequantum yield, extent of chain aggregation, and fluorescence quenching efficiency is discussed.