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Mechanical Behavior of Polymer Gels for RDCs and RCSAs Collection: NMR Imaging Study of Buckling Phenomena
Author(s) -
Hellemann Erich,
Teles Rubens R.,
Hallwass Fernando,
Barros W.,
NavarroVázquez Armando,
Gil Roberto R.
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201603333
Subject(s) - isotropy , anisotropy , buckling , relaxation (psychology) , polymer , materials science , proton nmr , residual , buckle , nuclear magnetic resonance , chemistry , composite material , optics , physics , psychology , social psychology , algorithm , computer science
Anisotropic NMR parameters, such as residual dipolar couplings (RDCs), residual chemical shift anisotropies (RCSAs) and residual quadrupolar couplings (RQCs or Δ ν Q ), 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.