NMR study of the long time,defect-controlled,magnetic reorientation of a nematic polymer liquid crystal |
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| Authors: | L N Gonçalves J P Casquilho J Figueirinhas C Cruz A F Martins |
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| Institution: | 1. Centre de Física da Matéria Condensada , Av. Prof. Gama Pinto 2, 1699 , Lisboa Codex , Portugal;2. Departamento de Ciěncia dos Materiais , Universidade Nova de Lisboa , 1699 , Lisboa Codex , Portugal;3. Departamento de Física , Universidade Nova de Lisboa , 1699 , Lisboa Codex , Portugal;4. Departamento de Física , Universidade Técnica de Lisboa , 1699 , Lisboa Codex , Portugal |
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| Abstract: | Abstract The magnetic field reorientation of an initially aligned sample of a nematic polymer liquid crystal was followed by proton NMR. Evolution to a metastable (banded) state was considered using a Rheo-NMR technique developed previously. Late stage reorientation was studied by taking into account the dynamics of defects following the formation of splay–bend walls. NMR spectra simulation allowed us to obtain the wall density as a function of time. This result, together with a defect-controlled wall dissolution model proposed by Rey 1], was used to complement the Rheo-NMR technique of measuring the viscoelastic parameters of nematic polymer liquid crystals. |
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