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Materials 2014, 7(2), 1384-1408;

Structural Characterization of Polymer-Clay Nanocomposites Prepared by Co-Precipitation Using EPR Techniques

Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
Centro Universitario de la Defensa, Ctra de Huesca s/n, 50090 Zaragoza, Spain
Author to whom correspondence should be addressed.
Received: 15 December 2013 / Revised: 16 February 2014 / Accepted: 17 February 2014 / Published: 21 February 2014
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)
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Polymer-clay nanocomposites (PCNCs) containing either a rubber or an acrylate polymer were prepared by drying or co-precipitating polymer latex and nanolayered clay (synthetic and natural) suspensions. The interface between the polymer and the clay nanoparticles was studied by electron paramagnetic resonance (EPR) techniques by selectively addressing spin probes either to the surfactant layer (labeled stearic acid) or the clay surface (labeled catamine). Continuous-wave (CW) EPR studies of the surfactant dynamics allow to define a transition temperature T* which was tentatively assigned to the order-disorder transition of the surfactant layer. CW EPR studies of PCNC showed that completely exfoliated nanoparticles coexist with agglomerates. HYSCORE spectroscopy in PCNCs showed couplings within the probe −assigned with DFT computations− and couplings with nuclei of the environment, 1H and 23Na for the surfactant layer probe, and 29Si, 7Li, 19F and 23Na for the clay surface probe. Analysis of these couplings indicates that the integrity of the surfactant layer is conserved and that there are sizeable ionic regions containing sodium ions directly beyond the surfactant layer. Simulations of the very weak couplings demonstrated that the HYSCORE spectra are sensitive to the composition of the clay and whether or not clay platelets stack. View Full-Text
Keywords: EPR; HYSCORE; spin label; polymer; composite; clay; nanocomposite EPR; HYSCORE; spin label; polymer; composite; clay; nanocomposite
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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Kielmann, U.; Jeschke, G.; García-Rubio, I. Structural Characterization of Polymer-Clay Nanocomposites Prepared by Co-Precipitation Using EPR Techniques. Materials 2014, 7, 1384-1408.

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