Materials science

The properties of numerous classes of technological materials depend intimately on molecular dynamics (for example, polymers, liquid crystals, emulsions, lubricants, coatings, etc.).
NMRD data obtained from FFC NMR relaxometry are rapidly becoming an essential complement of structural investigations and molecular dynamics simulation in elucidating the properties of heterogeneous complex systems.

click to enlarge

Polymers
Molecular motions in bulk polymers have a profound effect on their properties. Physical properties of elastomers, for example, cannot be understood at all without knowledge of their molecular mobility.
The figure shows proton NMRD profiles of melts of polyethylene glycol (PEG) with three different molecular weights (8000 Da in blue, 20000 Da in black and 35000 Da in red). Note that these can be most easily differentiated at very low magnetic field strengths. Indeed FFC NMR relaxometry could be a fast method of carrying out molecular weight determinations, especially as no particular sample preparation is required (no dissolution or filtration is needed).

Thanks to IFPEN, Paris, France for providing samples for this data.

click to enlarge


Liquid Crystals
Liquid crystal displays are widely used in the electronics industry. Molecular dynamics in liquid crystals are complex and closely related to their various phases.
The figure shows NMRD profiles of the fluorine nucleus of a calamitic liquid crystal known as 4DBF2, which contains two fluorine atoms. This liquid crystal exhibits a phase transition from isotropic to nematic phase between 67°C and 86°C. This change of phase is due to different organization of the crystals and is reflected in the two NMRD profiles obtained at 80°C and 90°C.

S. Bubici , L. Calucci, G. Ferrante, M. Geppi, Chemical Physics Letters 549 (2012) 27–31

click to enlarge



Electrolytes
Electrolytes are required for batteries, in particular in the electronics industry (see also section on Heteronuclei).
The figure shows proton NMRD profiles of an ionic liquid for a smart battery system at different salt concentrations (samples increase in salt concentration from A1 to A4). These results reflect the transport properties and molecular motions within the different concentrations of electrolyte solution. These results could be used to find improved electrolytes for battery systems.

click to enlarge


Solid-liquid interfaces
Molecular mobility at solid-liquid interfaces is important in catalysis, petrology and other fields (for example, relaxation data are already used to assay the distribution of pore sizes in rocks).
The NMRD profiles in the figure show different durations of hydration in cement paste. Indeed FFC NMR relaxometry is a non-destructive technique which can provide important information on the cement microstructure (specific area and pore size distribution). This is particularly important for hardened cement paste where the value of specific surface area is directly related to the mechanical performance of the material.

Korb et al. Cement and Concrete Research, 37 (2007) 295-302

click to enlarge


Porous materials: rocks
Understanding the pore-size in rocks is particularly important in the oil and gas industry. Indeed, FFC NMR relaxometry is particularly efficacious to characterize the architecture of pore space in water-saturated rocks and to estimate petro-physical properties, such as permeability and irreducible water saturation.
The figure shows how the relaxation times, T1, carried out at 4 different magnetic field strengths (diagram to the left) on a 1 inch diameter sample of feldspathic quartz sandstone rock saturated with water, can be used to understand the pore size distribution in the rock. The pore size distribution (diagram on the right) was obtained by means of a Laplace inversion algorithm (Upen algorithm).

click to enlarge



Natural materials research: Biochars
Energy efficiency of natural materials could be evaluated through FFC NMR relaxometry.
The figure shows three NMRD profiles for the wet biochars A, B (poplar and conifer wood chips) and C (grape-press residues). The profiles demonstrate the different water dynamics in these wet biochars which were retrieved by industrial thermo-chemical processes.

P. Conte et al. Journal of Soils and Sediments, 12:8 (2012) 1211