Polymère inorganique

Résumé

Les polymères inorganiques sont des polymères dont le squelette ne comporte pas d'atomes de carbone. Les polymères, tels les polymères modifiés silane, comprenant des composants organiques et inorganiques sont nommés des polymères hybrides ou polymères organo-minéraux. Un des exemples les mieux connus est le polydiméthylsiloxane. Il a un motif de répétition basé sur le silicium et l'oxygène : —[O-Si(CH3)2]n—. Le polythiazyle (polymère de nitrure de soufre), de formule , est, ce qui est hautement inhabituel, un polymère métallique supraconducteur à . Polymères naturels L'enchaînement covalent -Si-O-Si-O-Si-O- (appelé chaîne polysiloxanique), présent dans le polydiméthylsiloxane, est également la base de structures polymères inorganiques naturelles, uni-, bi- ou tridimensionnelles, dans la famille des silicates. Les sites libres de la chaîne polysiloxanique, au lieu d'être occupés par des groupes organiques pour former des polymères hybrides, peuvent l'être par des atomes

Source officielle

https://fr.wikipedia.org/wiki/Polym%C3%A8re_inorganique

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Hyperpolarization transfer pathways in inorganic materials

Snaedis Björgvinsdóttir, David Lyndon Emsley, Nicolas Luc Matthey, Pinelopi Moutzouri

Dynamic nuclear polarization can be used to hyperpolarize the bulk of proton-free inorganic materials in magic angle spinning NMR experiments. The hyperpolarization is generated on the surface of the material with incipient wetness impregnation and from there it is propagated towards the bulk through homonuclear spin diffusion between weakly magnetic nuclei. This method can provide significant gains in sensitivity for MAS NMR spectra of bulk inorganic compounds, but the pathways of the magnetization transfer into the material have not previously been elucidated. Here we show how two-dimensional experiments can be used to study spin diffusion from the surface of a material towards the bulk. We find that hyperpolarization can be efficiently relayed from surface sites to multiple bulk sites simultaneously, and that the bulk sites also engage in rapid polarization exchange between themselves. We also show evidence that the surface peaks can exchange polarization between different sites in cases of disorder.

2020

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Solid-state NMR spectroscopy is a well-established method to obtain atomic-level information about the structure of inorganic materials, but its use is often limited by low sensitivity. We review how solvent generated dynamic nuclear polarization can be used to increase sensitivity in solid-state NMR of inorganic materials, with emphasis on our recent method for hyperpolarization of proton-free bulk. We use selected examples to show how overall gains in sensitivity can be observed in both the surface and bulk spectra of inorganic compounds such as lithium titanate. The hyperpolarization methods reviewed here can be used to improve NMR sensitivity for a range of inorganic materials.

SWISS CHEMICAL SOC2021

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Sensitivity Enhancements in Lithium Titanates by Incipient Wetness Impregnation DNP NMR

Pierrick Berruyer, Snaedis Björgvinsdóttir, David Lyndon Emsley, Michael Allan Hope, Pinelopi Moutzouri

Solid-state NMR spectroscopy is a widely used method for investigating structural and electronic properties of inorganic materials, but its use is often limited by low sensitivity. Here, we show how solvent-generated dynamic nuclear polarization can be used to efficiently hyperpolarize the surface and bulk of lithium-containing inorganic materials, through impregnation with a radical-containing solution and transfer of hyperpolarization to lithium nuclei in the materials. This is demonstrated on two lithium titanates, Li2TiO3 and Li4Ti5O12, resulting in improved sensitivity of both Li-7 and Li-6 NMR spectra of the compounds. We also show that hyperpolarization is relayed from the surface toward the bulk for both Li-7 and Li-6 and demonstrate an overall gain in sensitivity of a factor similar to 90 for the bulk spectrum of Li-6 in Li4Ti5O12. The method can in principle be applied to increase sensitivity in the surface and bulk spectra of other inorganic lithium oxides.

AMER CHEMICAL SOC2020

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