Supramolecular membranes: synthesis and characterizations

This chapter contains an overview of supramolecular membranes, primarily focusing on polymeric membranes and mixed matrix membranes for gas separation applications. Other topics discussed are membranes that are synthesized from self-assembly, hydrogen bonding, π-π stacking of block copolymer systems, small molecules, and nanoparticles. The first recorded experiment for gas transport in polymeric membranes was performed by Thomas Graham in 1829, whichresulted in the formulation of two relationships in the years to come; gas diffusion and gas effusion, both becoming known as “Graham’s laws.” Extensive research has been performed and published, resulting in membranes being fabricated from a variety of organic or inorganic materials. The majority of commercially available membranes are made from synthetic organic polymers, due to the polymers ability to be controlled and tailored specifically. Improvements to the polymermatrices can be made with the addition of additives, which are known as mixed matrix membranes. Additives can introduce supplementary voids to increase the fractional free volume via intrinsic particle porosity or through repulsive interactions between polymer chains and particle surface. The surplus of void spaces can also act as adsorption sites for gas molecules, facilitating further gas transport. Polymeric membranes are susceptible to dense chain packing, reducing the fractional free volume and gas transport pathways. This chapter summarizes the recent research in utilizing supramolecular science for gas membrane separations