In this research project, we aim to prepare membranes having well-controlled pores with sizes in the nanometer range. Nanoporous membranes are promising materials for ultra/nanofiltration applications. Nanosized pores are required for the purification of water if small sized contaminants such as drugs and hormones need to be removed. With current technologies it is challenging to produce membranes having monodisperse nanosized pores. To meet this challenge, we are exploring the concept of block copolymer self-assembly.
Block copolymers consist of two or more covalently linked homopolymer subunits. Block copolymers can self-assemble into various morphologies such as spherical, cylindrical, lamellar or gyroidal depending on the ratio and length of the blocks and affinity between the blocks. As shown in part (1) of the Figure, addition of a homopolymer or selective solvent to one of the blocks will selectively swell that block. Subsequent removal of this homopolymer or selective solvent will result in pore formation in the material. For membrane applications pores need to connect top and bottom surfaces, for which standing cylinders or a gyroid morphology would be ideal. The size of the pores will be determined by the length of the (minority) block and the amount of homopolymer or selective solvent that has been added to the system.
We will produce self-cleaning membranes by introducing responsive blocks into the polymers. These blocks swell and shrink upon changing temperature or pH as shown in part (2) of the Figure. This will result in a change in pore diameter of the membrane which aid removal of contaminants, resulting in smart and effective cleaning of the membranes. Self-healing membranes will be produced by introducing non-covalent crosslinks in one of the blocks that forms the matrix of the membrane.