Tunable Inorganic Separation Membranes Templated by Block Copolymers

Tamar Segal-Peretz, Department of Chemical Engineering, Technion- Israel Institute of Technology, Haifa, Israel
Chun Zhou, Institute For Molecular Engineering, University Of Chicago, Chicago, United States
Muhammed Enes Oruc., Department Of Chemical Engineering, Yildiz Technical University, Istanbul, Turkey
Paul F. Nealey, Institute For Molecular Engineering, University Of Chicago, Chicago, United States


The growing demand for clean water, which is considered one of the most pervasive problems of humanity in the 21st century, requires the development of advanced nanoporous membranes for micro and nano pollutants removal and wastewater treatment processes. Block copolymer membranes have emerged in recent years as a promising class of organic membranes due to their highly uniform pore size and high porosity. However, block copolymer membranes are limited in their pore size and lack the attractive thermal, chemical, and mechanical properties that inorganic materials offer.

Here we harnessed block copolymer self-assembly of PS-b-PMMA (poly(styrene-b¬-methyl methacrylate) to template highly porous alumina membranes with ordered and uniform pore size and sub-20 nm pore diameter. Templating was performed by sequential infiltration synthesis (SIS), an emerging material synthesis strategy derived from atomic layer deposition (ALD), where sequentially introduced gaseous material precursors infiltrate and react selectively with the PMMA moieties, generating localized organic-inorganic hybrids that were subsequently converted to inorganic. Control over the alumina growth in the SIS process enabled to dial in the desired pore size and reduce it by 40%, as shown by electron microscopy (SEM, TEM) and small angle X-ray scattering (SAXS). 3D characterization, using TEM tomography, revealed that pores have non-tortuous pathways and an increase in pore size with depth. Finally, we demonstrated the alumina membrane separation properties by separating proteins as a function of the protein size and charge.