Eur. Phys. J. B 8, 225-231 (1999)
https://doi.org/10.1007/s100510050685

Formation of ordered micro-porous membranes

¹ Laboratoire des Matériaux et Structures du Génie Civil (CNRS-UMR 113) , CNRS/LCPC, 2 allée Kepler, 77420 Champs-sur-Marne, France
² Laboratoire de Recherche sur les Matériaux Polymères, CNRS/UPPA, Centre Hélioparc Pau-Pyrénées, 2 avenue du Président Angot, 64000 Pau, France

Received: 18 August 1998
Published online: 15 March 1999

Abstract

Regular micro-porous polymeric membranes have recently been discovered by rapidly evaporating a solution of CS₂ containing poly(p-phenylene)-block-polystyrene [CITE]. 1,2-dichloroethane (a chlorated solvent in which polystyrene gel phase has never been observed) is also found to produce ordered structures, which definitively excludes eventual effect of the gelation process during the membrane formation. The observation of the solution surface during the solvent evaporation reveals the growing of micron-sized water droplets trapped at the surface and forming compact aggregates. The study of the solution/water interface shows that the water droplets profile is in agreement with the pore shape observed in the membranes. Moreover, the copolymer was found to precipitate at the interface, forming a layer encapsulating the droplets and preventing their coalescence. In that way, the final structure results from the droplets stacking under the action of large surface currents. Finally, we argue that the decisive element in the formation of ordered structures is the ability of the polymer to precipitate at the solution/water interface, which seems to be related the star-polymer microstructure.