Synthesis of polysiloxane-imide membranes — application to the extraction of organics from water mixtures Original Research Article

The synthesis of new copolysiloxane-imide polymers was carried out from a,w-dimethylsiloxane oligomers and aromatic di-anhydrides (PMDA and 6FDA) to obtain soluble siloxane-imide based polymers (PSI) endowed both with organophile properties and good physical membrane properties. Synthesized PSI block copolymers had high weight contents of siloxane residue varying from 70 to 94 wt.%; their pervaporation properties were studied towards ethanol-water feed mixtures (EtOH: 10 and 50wt.%) at 40 °C. The two block copolymer series-fluorinated and not fluorinated — were both highly selective for ethanol removal from water. The registered pervaporation properties demonstrated that the membrane flux and the selectivity could be tailored with the polymer microstructures; in particular, much higher permeabilities were obtained with the fluorinated series than with the PDMA series whereas the alcohol selectivity was kept constant or slightly increased. These results showed that fluorinated PSI materials are promising candidates for the extraction of organic compounds from water mixtures.