Effect of Polydispersity on Fluorescence Quenching in Micelles Formed by Telechelic Associative Polymers

English, Rob J, Ratcliffe, Ian, Blanchard, R L and Parsons, B J (2007) Effect of Polydispersity on Fluorescence Quenching in Micelles Formed by Telechelic Associative Polymers.

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Abstract

Time-resolved fluorescence quenching studies, using pyrene as a probe for micellar environments in solutions of a telechelic associating polymer based on PEG with n-C12 (dodecyl) hydrophobic end groups, have been carried out to determine the aggregation number(s) of the micelles. At low [pyrene]/[hydrophobe] values, η, quencher-average aggregation numbers, Nq, calculated from the fitting of the fluorescence decay curves to the Infelta equation were found to decrease rapidly as η increased. By fitting the Nq vs η plots to a cubic curve [Warr, G. G.; Grieser, F. J. Chem. Soc., Faraday Trans. 1 1986, 82, 1813], this observation was shown to be consistent with a highly skewed, polydisperse distribution of micelle aggregation numbers, described by a weight-average aggregation number of 75 and a standard deviation of 86. For a given polymer concentration in the range 1.0−2.5 g dL-1, the fluorescence decay curves did not produce parallel log(I/I0) vs time plots, as would be expected for a monodisperse array of micelles. Instead, the plots showed a characteristic intersection. Simulation of these curves using Infelta-type equations could not reproduce this behavior, indicating that a more refined model may be needed. This detailed study of the distribution of aggregation number in associative telechelic polymers is discussed in the context of recent investigations [Meng, X.-X.; Russel, W. B. Macromolecules 2005, 38, 593], from which it is suggested that polydispersity of micelle size is to be expected as a normal feature of such systems.

Item Type:	Article
Additional Information:	Copyright © 2007 American Chemical SocietyMetadata only available from this repositoryThis article was originally published in Macromolecules - Journal of the American Chemical Society in 2007. The full article can be found at http://dx.doi.org/10.1021/ma0624649
Keywords:	Time-resolved fluorescence quenching, micelles, aggregation number, telechelic polymers
Divisions:	?? GlyndwrUniversity ??
Depositing User:	ULCC Admin
Date Deposited:	05 Oct 2011 09:14
Last Modified:	11 Dec 2017 20:06
URI:	https://wrexham.repository.guildhe.ac.uk/id/eprint/229

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