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.