Membranes are nowadays increasingly applied in the chemical and food industry, in bio- technology, medical life and for water purification. Most commercially available poly- meric porous membranes are prepared by immersion precipitation, a method based on diffusion induced phase separation when a cast film of a homogenous polymer solution is immersed into a non-solvent bath. The diffusional exchange of solvent and nonsolvent brings the film solution into an instable state resulting in liquid-liquid (l-l) and/or solid- liquid (s-l) demixing, depending on the type of polymer and the precipitation conditions employed. In this case, membrane pores form from the polymer-lean phase.
We recently started to investigate the preparation of porous membranes by polymerisation of bicontinuous microemulsions, which consist of interwoven water and oil channels sepa- rated by a surfactant monolayer. The underlying idea is to employ microemulsions that consist besides of water of an oil (apolar monomer) and a surfactant that contain the same or a similar polymerisable group. The thermodynamically controlled structure of the liquid microemulsion can then be solidified (frozen) during a fast polymerization, whereby main- ly the monomeric oil domains are converted into the polymeric membrane matrix. The advantage offered by microemulsion templating is the direct control of the pore size and morphology in the NF/UF filtration range.
Our first results on the polymerized bicontinuous microemulsion (PBM) membranes indi- cate that the interconnected pores are homogeneously distributed and that we can alter the pore size systematically keeping a high porosity. The nanostructured PBM-membranes therefore provide the potential of closing the gap between polymer and ceramic mem- branes: they show a precise separation due to a narrow and well-defined pore size distribution accompanied by a high productivity. So far PBM-membranes have not been applied to filter protein solutions and we want to study their protein retention and fractionation characteristics.
Nanostructured polymeric membranes
M.E. Avramescu and W.F.C. Sager
bicontinuous microemulsion
polymerised bicontinuous microemulsion oil
H2O
surfactant oil
H2O
surfactant
T.H. Chieng, L.M. Gan, W.K. Teo, K.L. Pey; Po- rous polymeric membranes by bicontinuous mi- croemulsion polymerisation: effect of anionic and cationic surfactants; Polymer, 37 (1996) 5917.
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•EVAL membranes →J Membr Sci 210, 155
→Scientific Report FZ-Jülich 2002/2003, 177
