Pushing the Limits of NMR Cryoporometry in Polymers from Nanometer to Micron

We report for the first time the nuclear magnetic resonance cryoporometry (NMRC) pore size distribution study of polypropylene homopolymer fluffs in a wide range from several nanometers up to almost one micrometer. The method, being applicable to fragile materials, provides an opportunity to employ a set of different probe molecules, such as dodecane and hexadecane in this study, to characterize the pore sizes and swelling effect of the polymers. The fluffs have been proven to be essentially macroporous with a minor mesopore part and negligible pore volume of micropores. The residual silica porosity analysis performed to understand the origin of polymer macroporosity emphasize the porosity hidden by the main mesoporosity peak of silicon oxide. This residual macroporosity would seem similar to the macroporosity of the PPH fluffs in terms of PSD. NMRC has been shown to provide robust interconsistent and reproducible pore size distributions of polymers and silicas within the range from several nanometer up to 2 micrometers.

Pushing the Limits of NMR Cryoporometry in Polymers from Nanometer to Micron

We report for the first time the nuclear magnetic resonance cryoporometry (NMRC) pore size distribution study of polypropylene homopolymer fluffs in a wide range from several nanometers up to almost one micrometer. The method, being applicable to fragile materials, provides an opportunity to employ a set of different probe molecules, such as dodecane and hexadecane in this study, to characterize the pore sizes and swelling effect of the polymers. The fluffs have been proven to be essentially macroporous with a minor mesopore part and negligible pore volume of micropores. The residual silica porosity analysis performed to understand the origin of polymer macroporosity emphasize the porosity hidden by the main mesoporosity peak of silicon oxide. This residual macroporosity would seem similar to the macroporosity of the PPH fluffs in terms of PSD. NMRC has been shown to provide robust interconsistent and reproducible pore size distributions of polymers and silicas within the range from several nanometer up to 2 micrometers.

Some Applications of a Field Programmable Gate Array Based Time-Domain Spectrometer for NMR Relaxation and NMR Cryoporometry

NMR Relaxation (NMRR) is an extremely useful quantitative technique for material science, particularly for studying polymers and porous materials. NMR Cryoporometry (NMRC) is a powerful technique for the measurement of pore-size distributions and total porosities. This paper discusses the use, capabilities and application of a newly available compact NMR time-domain relaxation spectrometer, the Lab-Tools Mk3 NMR Relaxometer & Cryoporometer [Lab-Tools (nano-science), Ramsgate, Kent, UK (2019)]. Being Field Programmable Gate Array based means that it is unusually compact, which makes it particularly suitable for the lab bench-top, in the field and also mobile use. Its use with a variable-temperature NMR probe such as the Lab-Tools Peltier thermo-electrically cooled variable-temperature (V-T) probe is also discussed. This enables the NMRC measurement of pore-size distributions in porous materials, from sub-nano- to over 1 micron sized pores. These techniques are suitable for a wide range of porous materials and also polymers. This instrument comes with a Graphical User Interface (GUI) for control, which also enables both online and offline analysis of the measured data. This makes it is easy to use for material science studies both in the field and in university, research institute, company and even school laboratories. The Peltier cooling gives the precision temperature control and smoothness needed by NMR Cryoporometry, particularly near the probe liquid bulk melting point. Results from example NMR Relaxation and NMR Cryoporometric measurements are given.