On the mechanism of formation of asymmetric ultra- and hyper-filtration membranes

A study has been made of the formation of membranes from solutions of poly(2,6-dimethyl-1, 4-phenylene oxide) (P.P.0.2) in trichloro-ethylene/alcohol mixtures and using methanol as the precipitation agent. The mechanism of the formation of the sponge - like structures proves to be a liquid - liquid phase separation phenomenon with nucleation and growth of the diluted phase. The waterpermeability of this extremely hydrophobic polymer membrane (which only is obtained for high percentages of octanol in the polymer solution) is possibly due to crystallization in the concentrated polymer regions, like the skin at the surface and the concentrated polymer phase which forms the matrix of the sponge-structure. The membranes prepared show good ultrafiltration properties.