Monitoring diffusion processes in nanoporous block copolymer membranes with high spatial and temporal resolution

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The proposed project aims at the investigation of transport processes in switchable diblock copolymer membranes with nanometer-sized pores with high temporal and spatial resolution. The membranes will be prepared by non-solvent induced phase separation (NIPS) from suitable amphiphilic block copolymers which will be synthesized using living/controlled polymerization techniques. The hydrophobic (polystyrene) block will form the matrix of the structures and the hydrophilic segments covers the pore walls. As hydrophilic block we plan to use a material, which solubility in aqueous media can be reversibly altered through external stimuli. Possible envisioned triggers are changes in the pH (e.g., poly(2-dimethylaminoethyl methacrylate), PDMAEMA), temperature (copolymers from PDMAEMA and poly(methyl methacrylate), PMMA), or the irradiation with light of a specific wavelength (copolymers of poly(N-isopropylmethacrylamide), PNiPAAm, and poly(spiropyrane methacrylate), PSPMA). The transport processes will be monitored using 3D single particle optical tracking (3D-SPOT) with fluorescently labeled particles of suitable size (d < 50 nm). The recorded diffusion paths will be compared with reconstructed 3D models of membranes by transmission electron microscopy tomography (TEMT) using semi-thin microtome slices (200-300 nm). Prior to that, the membranes will be embedded within suitable resins.