Abstract:

Composite membranes (also referred to as hybrid and mixed-matrix membranes/MMMs) comprise of nanoparticles and polymer matrix, which offer advantages from the synergetic effects among their constituents. This type of membrane has been widely applied in gas separation, nanofiltration, desalination, etc. The characteristics of composite membranes at the nanoscale are detrimental. However, they have not been well investigated due to instrumentation limitations. Herewith, we introduced nano-FTIR spectroscopy, a combined AFM-FTIR technique, to unveil the nanodomain properties of the composite membranes, including the encapsulation of the nanomaterials by the polymer matrix, their chemical footprint, and the variation in the local chemistry of the membranes. This unique characterization technique was applied to study composite carbon molecular sieve (CCMS) membrane containing fullerenols, MMMs containing metal-organic frameworks (MOFs), and interpenetrated polymer network (IPN) membranes. In the fabrication of CCMS membrane, the pyrolysis process led to the formation of chemical inhomogeneity at nanodomain level, that was observed from the variability in the nano-FTIR peak positions. Furthermore, the fullerenol nanomaterials were found to be fully enveloped by the polymer matrix, as indicated by the absence of the nano-FTIR spectra characteristic of nanoparticle. In the MMMs, the MOF nanoparticles on the membrane surfaces were found to be uncovered by the polymer matrix, as identified from a characteristic nano-FTIR peak of the MOF. This information is essential to confirm the molecular transport mechanism through the MOF pores instead of the polymer matrix. The experimental nanofiltration results matched well with the theoretical prediction based on pore flow model. By using nano-FTIR spectroscopy, we have also successfully visualized the heterogenous polymer networks at nanoscale. Although macroscopically the IPN membrane seems to be homogenous, however we observed polymer domain at nanoscale. The novelty in the applications of nano-FTIR spectroscopy will open a broader way to unveil the properties of various composite/hybrid materials that are previously unable to be characterized.

Bio:

Dr. Hardian is currently a Research Scientist at the group of Prof. Gyorgy Szekely at KAUST. His main research interest encompasses the development of advanced membranes (including polymer and composite nanomaterials), and the application of advanced materials characterization techniques (spectroscopy and imaging) to investigate the material properties. Dr. Hardian obtained his BSc in Chemistry from Indonesia University of Education followed by an MSc in Environmental and Energy Management from University of Twente (Netherlands). He also received an Erasmus Mundus scholarship to pursue a double MSc degree in Materials Science from INP Grenoble (France) and TU Darmstadt (Germany). Following that, he was awarded a Marie Sklodowska Curie Action (MSCA) scholarship to complete his PhD in Materials Science from Aix-Marseille University (France), where he worked on engineering defects in metal-organic frameworks (MOFs) for molecular separation, under the supervision of Dr. Philip Llewellyn.