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Orientador(es)
Resumo(s)
We report the use of 2 H NMR spectroscopy to study the director orientation in two nematic solutions of poly(c-benzyl-L-glutamate) (PBLG) in m-cresol during simple shear flow and after its sudden cessation. In the range of
applied shear rates ðc_ ¼ 5 ... 150 s 1Þ, a steady-state NMR line shape is reached after a deformation of a few hundred units. Two different line shapes occur that can be related to distinct shear responses in mechanical rheology: the tumbling=wagging and the flow-aligning regimes. The relaxation after cessation of the shear is similar for both cases and essentially follows the ‘‘inhomogeneous reorientation’’ regime known from sudden-rotation NMR experiments. A fit of the relaxation curves indicates that the tumbling parameter k is (slightly) less than one, as expected for a tumbling system.
Descrição
Palavras-chave
liquid crystal polymer PBLG Rheo-NMR
Contexto Educativo
Citação
Leal CR, Klink J, Martins A – Some Aspects of the Rheo-Nmr Behavior of the Lyotropic Liquid Crystal Poly(γ-BENZYL-L GLUTAMATE) in m-Creso. Molecular Crystals and Liquid Crystals. ISSN 1542-1406. 2004, 420(1): 35-45. https://doi.org/10.1080/15421400490478344
Editora
Taylor & Francis