Abstract
Spin-lattice and spin-spin relaxation times are one of the most attractive tools in the solid-state nuclear magnetic resonance spectroscopy to evaluate the level of clay dispersion in the nanocomposite matrices. The efficiency of the relaxation processes can be used to evaluate the nanoparticles intermolecular interactions and, consequently, the dispersion of them in the polymer matrix, the molecular dynamic of the hybrid compounds, as well as the molecular domains formation in an organic material. The determination of relaxation parameters was carried out to evaluate the organoclay exfoliation and intercalation process in the polymeric matrix, in addition to their dispersion and distribution in the matrix. The proton NMR relaxation data showed that the polymeric nanomaterials investigated presented good intermolecular interaction that promoted good nanoparticles dispersion and distribution in the hybrid materials. The proportion of 2% clay promoted a greater heterogeneity in the matrix compared to other ratios; 1% clay influenced only to the higher molecular rigidity phase; and 3% clay had a decrease in heterogeneity compared to 2% though still influenced the matrix as a whole. These results prove the efficiency of NMR technique in the evaluation of nanofillers interaction with polymer matrices, as well as their dispersion and distribution.
Highlights
Solid-state nuclear magnetic resonance spectroscopy (NMR) provides powerful techniques for measurement ofHow to cite this paper: da Silva, P.S.R.C., Menezes, L.R. and Tavares, M.I.B. (2016) The Influence of Organo-Clay Ratio in the HIPS-organically modified montmorillonite (OMMT) Nanocomposites Analyzed by Proton Spin-Lattice and Spin-Spin Relaxation Times
Because of this broad coverage, the relaxation parameters are of great value to understand the dispersion of the nanoparticles in the polymer matrix, the interaction between nanocomposite components, the molecular dynamic of the hybrid compound, and the molecular domains formation in an organic material [7]
For the samples with 2% and 3% of clay it was observed a sum of paramagnetic effect and the dominant mechanisms of relaxation process; we postulate that a short spatial proximity exists between the macromolecules and the metals in these samples. These observations are consistent with the organoclay being better dispersed and distributed in the polymer matrix of these samples. b) Spin-lattice relaxation time in the rotating frame—T1ρ It is known that T1ρH is measured directly in the cross polarization experiments by a series of 13C cross polarization magic angle spinning (CPMAS) spectra in which the contact time is incrementally increased
Summary
Solid-state nuclear magnetic resonance spectroscopy (NMR) provides powerful techniques for measurement of. The spin-lattice relaxation parameters involve changes in thermal equilibrium of spin systems and the responses of them are intrinsically related to the system’s molecular dynamic that is derived from the morphology of the systems [6] Because of this broad coverage, the relaxation parameters are of great value to understand the dispersion of the nanoparticles in the polymer matrix, the interaction between nanocomposite components, the molecular dynamic of the hybrid compound, and the molecular domains formation in an organic material [7]. According to the spin-spin relaxation mechanism this parameter is less influenced by paramagnetic metals These relaxation parameters have been used to analyze the molecular dynamic behavior in solids, such as polymers, and other kind of materials, and can be envisioned as good tools for the evaluation of polymer nanocomposites, as well. The T1ρH was extracted from the series of 13C CPMAS decay intensities of C-1 carbon
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