Hydrophobic surface properties of fluoropolyetherimide blends for pervaporation membranes

The well‐known polyetherimide (ULTEM 1000) is obtained by step‐reaction of bisphenol. A diphthalic anhydride (BAPA) with m‐phenylene diamine and newly related fluorinated poly etherimides synthesized from BAPA and 2,3‐bis(2,2,3,3,4,4,5,5,5‐nonafluoropentyl)butan‐1,4 diamine (NFD) led to compatible blends over the entire range of composition. Miscible one‐phase blends have been suggested by a good correlation of Tg versus NFD monomer unit weight fraction (w) (Fox and Couchman equations) and a regular morphology by scanning electron microscopy. Surface energy of blend films fell from 45.3 to 27.4 mJ m−2 for w ≥ 0.1 corresponding to a NFD molar fraction y ≥ 0.06. Cast‐evaporated films from fluorinated copolyetherimides and blends with y < 0.15 were ductile and gave conveniently hydrophobic non‐porous membranes that withstood the experimental conditions of pervaporation tests. Copyright © 2003 Society of Chemical Industry