Mechanical Behavior of Polymer Gels for RDCs and RCSAs Collection: NMR Imaging Study of Buckling Phenomena |
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| Authors: | Erich Hellemann Dr Rubens R Teles Prof Dr Fernando Hallwass Prof Dr W Barros Jr Dr Armando Navarro‐Vázquez Prof Dr Roberto R Gil |
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| Institution: | 1. Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA, USA;2. Departamento de Química Fundamental, Universidade Federal de Pernambuco, Recife, PE, Brazil;3. Departamento de Física, Universidade Federal de Pernambuco, Recife, PE, Brazil |
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| Abstract: | Anisotropic NMR parameters, such as residual dipolar couplings (RDCs), residual chemical shift anisotropies (RCSAs) and residual quadrupolar couplings (RQCs or ΔνQ), appear in solution‐state NMR when the molecules under study are subjected to a degree of order. The tunable alignment by reversible compression/relaxation of gels (PMMA and p‐HEMA) is an easy, user‐friendly, and very affordable method to measure them. When using this method, a fraction of isotropic NMR signals is observed in the NMR spectra, even at a maximum degree of compression. To explain the origin of these isotropic signals we decided to investigate their physical location inside the NMR tube using deuterium 1D imaging and MRI micro‐imaging experiments. It was observed that after a certain degree of compression the gels start to buckle and they generate pockets of isotropic solvent, which are never eliminated. The amount of buckling depends on the amount of cross‐linker and the length of the gel. |
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| Keywords: | anisotropy compression/relaxation method gels NMR spectroscopy |
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