Asymmetric membranes by wet phase inversion of phenylated polyphenylene

Asymmetric membranes of phenylated polyphenylene were prepared by wet phase inversion. The polyphenylene (M_n = 62 kDa, PD = 2.3) was prepared by Diels-Alder polymerization of 1,4-bis(tetraphenylcyclopentadienonyl)benzene with 1,4-diethynylbenzene at 180°C. Solvents and non-solvents were experimentally identified and solvent: non-solvent systems were evaluated by the quality of the resulting membranes. Cyclohexanone/n-butanol (88: 12) as solvent and n-butanol as the non-solvent were found to afford the best asymmetric membranes with minimal defects. Membranes (20-30 μm thick) from coagulating 11.5 wt % polyphenylene from cyclohexanone/n-butanol in n-butanol baths exhibited 250-300 nm, non-porous skins overlaying 20-30 μm of open-celled, spongiform structure. Due to a relatively high glass transition temperature of 370°C, the phenylated polyphenylene membranes retained their porosity to 200°C higher than polysulfone asymmetric membranes.