Vertically Oriented Nanoporous Block Copolymer Membranes for Oil-Water Separation and Filtration

The separation of oil from water and filtration of aqueous solutions and dispersions are critical issues in the processing of waste and contaminated water treatment. Membrane-based technology has been proven as an effective method for the separation of oil from water. In this research, novel vertical nanopores membrane, via oriented cylindrical block copolymer (BCP) films, suitable for oil/water filtration has been designed, fabricated and tested. We used ultrathin (~100 nm) model BCP membranes, e.g. poly(styrene-block-methymethacrylate) (PS-b-PMMA), as the active top nanofiltration layer, processed using a variety of methods, from oven annealing to roll-to-roll (R2R) based cold zone annealing (CZA), and use of plasticizing additives to obtain vertical orientation. Nanopores are created using ultraviolet (UV) irradiation and solvent based selective etch of one block, e.g. PMMA cylinders, to form vertically oriented nanopores as a novel feature compared to meandering nanopores in other reported BCP systems. The cylindrical nanochannels are hydrophilic, and can have a uniform pore size as small as 23 nm, and a narrow pore size distribution and a high nanopore density ~420 per sq. micron as characterized by atomic force microscopy (AFM), grazing incidence small angle x-ray scattering. Fluid flux as well as oil/water separation test results will be reported. The bottom supporting layer is a conventional microporous polyethersulfone (PES) membrane. The created asymmetric membrane is demonstrated to be effective for oil/water extraction.