On studying asymmetric membranes made from polymethylmethacrylate/xylene by the thermal-inversion method.

Both polydisperse and monodisperse PMMA/xylene phase diagrams have been determined successfully by applying the optical density method. The changes in optical density for the polydisperse PMMA system are not as dramatic as the changes for the monodisperse PMMA system. Through the thermal-inversion process, the asymmetric membranes can be successfully made for this PMMA/xylene system. In the later stages of phase separation by spinodal decomposition, the flow properties of the PMMA/xylene system play a vital role in determining the final membrane microstructure. During the very early stage of phase separation by spinodal decomposition, a membrane with lacy structure results. In contrast, during the later stage of phase separation, a membrane structure with small pores dispersed in the polymer matrix results.