STUDIES ON SILICONE-GRAFTED COPOLYIMIDES .4. SYNTHESIS AND PROPERTIES OF BRANCHING COPOLYIMIDES WITH FLUOROALKYL AND POLY(DIMETHYLSILOXANE) SIDE-CHAINS

Soluble copolyimides containing fluorinated alkoxy (FA) groups and poly(dimethylsiloxane) (PDMS) side chains were prepared by means of polycondensation of 2,2,2-trifluoro-1-(trifluoro-methyl)ethylidene diphthalic anhydride (6FDA) with 4,4'-oxydianiline (ODA), 3-(3,5-diaminobenzyloxy)propyl-terminated poly(dimethylsiloxane) (DAB-PDMS) and 3,5-diaminobenzyl fluoroalkyl ether (DAB-FA) followed by imidation. Tough menbranes were prepared from the copolyimides by a solvent casting method. The introduction of FA groups and PDMS side chains remarkably increases the hydrophobicity of the copolyimide film, the contact angle of water being raised to 124-degrees-C. Introduction of FA groups in the copolyimide resulted also in an increase of the permselectivity of oxygen toward nitrogen of the membrane. Furthermore, the selective permeation of organic liquids was observed in the pervaporation of aqueous organic solutions through the membrane.