Contribution of the methine group to the transverse1H NMR relaxation in vulcanized natural rubbers

Transverse 1H NMR relaxation experiments in vulcanized natural rubber (NR) samples above the glass transition temperature (Tg) are reported on. Natural rubber samples with the same initial chemical composition but different times of cure were studied. The distinct feature of this study as compared t...

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Autores principales: Marzocca, Angel José, Cerveny, Silvina
Publicado: 2004
Materias:
Anisotropy
Crosslinking
Dynamics
Elastomers
Glass transition
Magnetization
Nuclear magnetic resonance
Protons
Swelling
Dipolar couplings
Methine group
Polymer chains
Spin-spin relaxation
Rubber
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00249297_v37_n15_p5624_Steren
http://hdl.handle.net/20.500.12110/paper_00249297_v37_n15_p5624_Steren
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id paper:paper_00249297_v37_n15_p5624_Steren
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spelling paper:paper_00249297_v37_n15_p5624_Steren2023-06-08T14:52:34Z Contribution of the methine group to the transverse1H NMR relaxation in vulcanized natural rubbers Marzocca, Angel José Cerveny, Silvina Anisotropy Crosslinking Dynamics Elastomers Glass transition Magnetization Nuclear magnetic resonance Protons Swelling Dipolar couplings Methine group Polymer chains Spin-spin relaxation Rubber Transverse 1H NMR relaxation experiments in vulcanized natural rubber (NR) samples above the glass transition temperature (Tg) are reported on. Natural rubber samples with the same initial chemical composition but different times of cure were studied. The distinct feature of this study as compared to previous works is that the contribution to the total transverse 1H magnetization of the methine group of the monomeric unit and the contribution of the methyl and methylene functional groups are analyzed independently. The results of these experiments show that for short delay times the decay of the 1H transverse magnetization of the methine groups is slower than that of the methyl/methylene groups. Consequently, the methine 1H contribution to the total transverse magnetization can be distinguished from the contribution of the other functional groups. A slow relaxing contribution to the total transverse 1H magnetization in NR samples, similar to the one reported on in this work, has been described in the literature.1 However, the contribution was attributed to 1H in dangling chain ends experiencing fast anisotropic motions. Here, we show that, on the contrary, the contribution is indeed produced by the methine groups in cross-linked chains. Values for the residual dipolar second moment, fraction of dangling chain ends, and spin-spin relaxation constant time T2 were obtained from the fit of the transverse 1H relaxation curves of the methine and methyl/methylene groups independently. The values obtained for these parameters suggest that the protons in the polymer chains sense the same microscopic properties of the material independently of the functional group where they are. The slower decay of the methine magnetization is caused in part by a weaker dipolar interaction for the methine proton with its nearest 1H neighbors as compared to the intragroup dipolar couplings in methyl or methylene groups. Fil:Marzocca, A.J. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Cerveny, S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 2004 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00249297_v37_n15_p5624_Steren http://hdl.handle.net/20.500.12110/paper_00249297_v37_n15_p5624_Steren
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Anisotropy
Crosslinking
Dynamics
Elastomers
Glass transition
Magnetization
Nuclear magnetic resonance
Protons
Swelling
Dipolar couplings
Methine group
Polymer chains
Spin-spin relaxation
Rubber
spellingShingle Anisotropy
Crosslinking
Dynamics
Elastomers
Glass transition
Magnetization
Nuclear magnetic resonance
Protons
Swelling
Dipolar couplings
Methine group
Polymer chains
Spin-spin relaxation
Rubber
Marzocca, Angel José
Cerveny, Silvina
Contribution of the methine group to the transverse1H NMR relaxation in vulcanized natural rubbers
topic_facet Anisotropy
Crosslinking
Dynamics
Elastomers
Glass transition
Magnetization
Nuclear magnetic resonance
Protons
Swelling
Dipolar couplings
Methine group
Polymer chains
Spin-spin relaxation
Rubber
description Transverse 1H NMR relaxation experiments in vulcanized natural rubber (NR) samples above the glass transition temperature (Tg) are reported on. Natural rubber samples with the same initial chemical composition but different times of cure were studied. The distinct feature of this study as compared to previous works is that the contribution to the total transverse 1H magnetization of the methine group of the monomeric unit and the contribution of the methyl and methylene functional groups are analyzed independently. The results of these experiments show that for short delay times the decay of the 1H transverse magnetization of the methine groups is slower than that of the methyl/methylene groups. Consequently, the methine 1H contribution to the total transverse magnetization can be distinguished from the contribution of the other functional groups. A slow relaxing contribution to the total transverse 1H magnetization in NR samples, similar to the one reported on in this work, has been described in the literature.1 However, the contribution was attributed to 1H in dangling chain ends experiencing fast anisotropic motions. Here, we show that, on the contrary, the contribution is indeed produced by the methine groups in cross-linked chains. Values for the residual dipolar second moment, fraction of dangling chain ends, and spin-spin relaxation constant time T2 were obtained from the fit of the transverse 1H relaxation curves of the methine and methyl/methylene groups independently. The values obtained for these parameters suggest that the protons in the polymer chains sense the same microscopic properties of the material independently of the functional group where they are. The slower decay of the methine magnetization is caused in part by a weaker dipolar interaction for the methine proton with its nearest 1H neighbors as compared to the intragroup dipolar couplings in methyl or methylene groups.
author Marzocca, Angel José
Cerveny, Silvina
author_facet Marzocca, Angel José
Cerveny, Silvina
author_sort Marzocca, Angel José
title Contribution of the methine group to the transverse1H NMR relaxation in vulcanized natural rubbers
title_short Contribution of the methine group to the transverse1H NMR relaxation in vulcanized natural rubbers
title_full Contribution of the methine group to the transverse1H NMR relaxation in vulcanized natural rubbers
title_fullStr Contribution of the methine group to the transverse1H NMR relaxation in vulcanized natural rubbers
title_full_unstemmed Contribution of the methine group to the transverse1H NMR relaxation in vulcanized natural rubbers
title_sort contribution of the methine group to the transverse1h nmr relaxation in vulcanized natural rubbers
publishDate 2004
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00249297_v37_n15_p5624_Steren
http://hdl.handle.net/20.500.12110/paper_00249297_v37_n15_p5624_Steren
work_keys_str_mv AT marzoccaangeljose contributionofthemethinegrouptothetransverse1hnmrrelaxationinvulcanizednaturalrubbers
AT cervenysilvina contributionofthemethinegrouptothetransverse1hnmrrelaxationinvulcanizednaturalrubbers
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