Using Pyrene Excimer Fluorescence To Probe Polymer Diffusion in Latex Films
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Date
2017-02-28
Authors
Casier, Remi
Gauthier, Mario
Duhamel, Jean
Journal Title
Journal ISSN
Volume Title
Publisher
American Chemical Society
Abstract
This study introduces a simple technique that can be used to quantitatively probe interparticle polymer diffusion (IPD) between adjacent particles in a latex film using pyrene excimer fluorescence (PEF). To demonstrate the validity of the technique, four latexes were prepared: two pyrene-labeled poly(n-butyl methacrylate) (Py-PBMA) latexes and two nonfluorescent PBMA latexes. The two pairs of Py-PBMA and PBMA latexes had similar distributions of polymer molecular weight and particle diameters. Mixtures of latex dispersions having a composition of 5 wt % Py-PBMA latex and 95 wt % nonfluorescent PBMA latex were cast into films. Fluorescence spectra of the films were acquired, and the ratio of the fluorescence intensities for the pyrene monomer (I-M) and excimer (I-E) was calculated to determine the I-E/I-M ratio. The latex films were then annealed at a constant temperature set between 75 and 119 degrees C. The fraction of mixing (f(m)), representing the amount of polymer having diffused out of a particle, was determined by monitoring the change in the I-E/I-M ratio as a function of annealing time. The f(m) profiles were then analyzed to yield the polymer diffusion coefficients, and the apparent activation energy (E-a) for diffusion was found to equal 179 +/- 7 and 170 +/- 12 kJ mol(-1) for the high and low molecular weight chains, respectively. The c(1) and c(2) parameters in the WLF equation were calculated to be 11 +/- 2 and 170 +/- 30 K, respectively. The E-a values and c(1) and c(2) parameters were in close agreement with values previously found for PBMA by other techniques, suggesting that the PEF experiments provide a valid experimental means to probe IPD in latex films. The superiority of PEF over earlier procedures includes the extreme simplicity of the experimental method that involves the labeling of a single latex particle and the use of ratios of fluorescence intensity. It opens new research venues in the study of IPD during latex film formation.
Description
This document is the Accepted Manuscript version of a Published Work that appeared in final form in Macromolecules, copyright © American Chemical Society after peer review and technical editing by publisher. To access the final edited and published work see https://dx.doi.org/10.1021/acs.macromol.6b02726
Keywords
Co-Methyl Methacrylate), High-Molecular-Weight, Energy-Transfer, Oxygen Diffusion, Poly(Methyl Methacrylate), Poly(Butyl Methacrylate), Temperature-Dependence, Mechanical-Properties, Particle Coalescence, Composite Films