Synthesis and Optoelectronic Properties of Nonpolar Polyrotaxane Insulated Molecular Wires with High Solubility in Organic Solvents
Framptom, M. J. F.
; Sforazzini, G. S.
; Brovelli, S. B.
; Latini, G.
; Townsend, E. T.
; Williams, C. C. W.
; Zalewski, L. Z.
; Kaka, N. S. K.
; Sirish, M. S.
Advanced Functional Materials Vol. 18, Nº , pp. 1 - 10, October, 2008.
ISSN (print): 1616-301X
Journal Impact Factor: 6,808 (in 2008)
Digital Object Identifier: 10.1002/adfm.200800653
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Hydrophilic polyanionic conjugated polyrotaxanes are readily synthesized in water by Suzuki coupling, but their high polarity
and ionic nature limit the potential applications of these materials. Here, we demonstrate three methods for transforming these
polar polyelectrolytes into nonpolar lipophilic insulated molecular wires. A water-soluble polyfluorene-alt-biphenylene bcyclodextrin
(CD) polyrotaxane was converted into nonpolar derivatives by methylation of the carboxylic acid groups with
diazomethane and conversion of the hydroxyl groups of the CDs to benzyl ethers, trihexylsilyl ethers, benzoyl esters, and
butanoate esters to yield polyrotaxanes that are soluble in organic solvents such as chloroform and cyclohexane. Elemental
analysis, NMR spectroscopy, and gel permeation chromatography (GPC) data support the proposed structures of the organicsoluble
polyrotaxanes. The extents of reaction of the polyrotaxane CD hydroxyl groups were 55% for trihexylsilyl chloride/
imidazole; 81% for benzyl chloride/sodium hydride; 72% for benzoyl chloride/pyridine/4-dimethylaminopyridine; and 98%
butanoic anhydride/pyridine/4-dimethylaminopyridine. Alkylation, silylation, and esterification increase the bulk of the
encapsulating sheath, preventing interstrand aggregation, increasing the photoluminescence efficiency in the solid state and
simplifying the time-resolved fluorescence decay. The organic-soluble polyrotaxanes were processed into polymer light-emitting
diodes (PLEDs) from solution in nonpolar organic solvents, thereby excluding ionic impurities from the active layer.