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Length and Time-Dependent Rates in Diffusion-Controlled Reactions with Conjugated Polymers

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Paiboon Sreearunothai^†^‡, Sadayuki Asaoka^§, Andrew R. Cook^† and John R. Miller*^†

Chemistry Department, Brookhaven National Laboratory, Upton, New York 11793–5000 and Chemical Resources Laboratory, Tokyo Institute of Technology, Yokohama, 226–8503, Japan

J. Phys. Chem. A, 2009, 113 (12), pp 2786–2795

DOI: 10.1021/jp809413x

Publication Date (Web): March 4, 2009

* To whom correspondence should be addressed., †

Chemistry Department, Brookhaven National Laboratory.

, ‡

Present address: Sirindhorn International Institute of Technology, Thammasat University – Pathum Thani 12121, Thailand.

, §

Chemical Resources Laboratory, Tokyo Institute of Technology.

Section:

Physical Properties of Synthetic High Polymers

Abstract

Rate constants for diffusion-controlled reactions of solvated electrons with conjugated fluorene oligomers (oF) and polymers (pF) were measured in liquid tetrahydrofuran (THF). Preparative gel permeation chromatography (GPC) was used to separate the polyfluorenes into fractions having narrowed distributions of lengths. Both oF and pF’s were used in determinations of the attachment rate constants k_inf as a function of length, where k_inf refers to the rate coefficients at long times where they are indeed constant. The results find that in going from oF₁ to pF₁₃₃, k_inf increases by a factor of 16, which is much smaller than that of the 133-fold increase in length. The extent of this increase and its change with length are in excellent agreement with published theoretical models that describe diffusion to long thin objects as either prolate spheroids or one-dimensional arrays of spheres. As the concentration of polymer was increased, the effects of large transient terms in the rate constant were observed. As predicted by the Smoluchowski diffusion equation, with modifications by more contemporary theorists, these transient effects are larger and persist to longer times for the larger molecules. For the longest molecule, pF₁₃₃, k(t) increases by more than a decade at short times. In that case, the “transient term” becomes dominant and the rate coefficient is approximately proportional to the square of the effective reaction radius in contrast to the linear dependence usual for diffusional reactions. The size of these transient effects and their quantitative confirmation are unprecedented.

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This article has been cited by 3 ACS Journal articles (3 most recent appear below).

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The Journal of Physical Chemistry Letters2011 2 (23), 2951-2958
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  The Journal of Physical Chemistry Letters2011 2 (23), 2951-2958
  We discuss how the mobility of a charge moving along a conjugated polymer chain is affected by different types of disorder. The intrachain mobility has been determined by using pulse radiolysis in combination with microwave conductivity measurements. The ...
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Sudden, “Step” Electron Capture by Conjugated Polymers
Andrew R. Cook, Paiboon Sreearunothai, Sadayuki Asaoka, and John R. Miller
The Journal of Physical Chemistry A2011 115 (42), 11615-11623
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Negative Polaron and Triplet Exciton Diffusion in Organometallic “Molecular Wires”
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Journal of the American Chemical Society2011 133 (29), 11289-11298
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  Journal of the American Chemical Society2011 133 (29), 11289-11298
  The dynamics of negative polaron and triplet exciton transport within a series of monodisperse platinum (Pt) acetylide oligomers is reported. The oligomers consist of Pt–acetylide repeats, [PtL2–C≡C–Ph–C≡C−]n (where L = PBu3 and Ph = 1,4-phenylene, n = 2, ...
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