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Solid-State Nuclear Magnetic Resonance Characterization of Residual 23Na in Aramid Fibers
被引:7
作者:
Brauckmann, J. Ole
[1
,2
]
Verhoef, Rene
[3
]
Schotman, Anton H. M.
[3
]
Kentgens, Arno P. M.
[2
]
机构:
[1] TI COAST, Sci Pk 904, NL-1098 XH Amsterdam, Netherlands
[2] Radboud Univ Nijmegen, Inst Mol & Mat, Magnet Resonance Res Ctr, Heyendaalseweg 135, NL-6525 AJ Nijmegen, Netherlands
[3] Teijin Aramid BV, Res & Innovat Ctr, POB 5153, NL-6802 ED Arnhem, Netherlands
关键词:
ELECTRIC-FIELD GRADIENTS;
QUADRUPOLAR NUCLEI;
NMR;
SODIUM;
KEVLAR-49;
MAS;
TEREPHTHALAMIDE);
MICROVOIDS;
IONOMERS;
SPECTRA;
D O I:
10.1021/acs.jpcc.9b02071
中图分类号:
O64 [物理化学(理论化学)、化学物理学];
学科分类号:
070304 ;
081704 ;
摘要:
In aramid (para-phenylene terephthalamide) fibers, small concentrations of sodium ions are present as remnants of the neutralization step in the production. This is thought to relate to the long-term stability of the fibers. Our study shows that most of the sodium ions are accessible by water. Fitting the Na-23 NMR spectra at two magnetic fields reveals a large distribution in both quadrupolar interaction and isotropic chemical shift, indicating substantial structural variations in the direct vicinity of the ions. All these observations imply that, upon drying, the sodium ions reside in a single pool with a very disordered environment. This implies that fibers consist of crystallites that are packed in such a way that end groups are not directly exposed for coordination with sodium. The sodium resides in intercrystalline regions of the fibers, that is, cracks and voids, most likely in the form of sodium sulfate at various stages of (residual) hydration.
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页码:14439 / 14448
页数:10
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