Synthesis and characterization of new highly permeable polyamideimides from dianhydride monomers containing amide functions: An application to the purification of a fuel octane enhancer (ETBE) by pervaporation

Six polyamideimides (PAI) were synthesized from six dianhydride monomers co ntaining amide functions. The dianhydride monomers were obtained from the r eaction of trimellitic anhydride chloride with six aromatic diamines-1,4,4- phenylenediamine, 2,2-bis(4-aminophenyl) propane, 4,4'-oxydianiline, 4,4'-m ethylenedianiline, 1,1-bis(4-aminophenyl)cyclohexane, and bis(4-aminophenyl )sulfone-by a low-temperature condensation with yields ranging from 35 to 9 8% depending on the monomer solubility in organic media. The monomers were characterized by Fourier transform infrared (FTIR) and H-1 NMR. In accordan ce with a synthesis scheme implying the reaction of a macrodiisocyanate wit h dianhydride monomers containing amide functions, six PAIs with a highly f lexible soft block (polytetramethylene glycol PTMG 650) were synthesized wi th inherent viscosities ranging from 0.38 to 1.3 dL/g. Their characterizati on by FTIR and 1H NMR fully confirmed their chemical structure. The strong physical crosslinking provided by polar hard blocks containing up to eight aromatic rings enabled the casting of PAI films that were very tough in the dry state and could withstand exposure to rather strong solvating media (e .g., ethers, alcohols, and chlorinated solvents). First experiments showed these materials could be good candidates for membrane-separation applicatio ns. They revealed interesting features for the separation of organic aproti c-protic mixtures as shown by the first results obtained for the purificati on of a fuel octane enhancer (ethyl-tert-butyl ether) used in the European Community. (C) 2000 John Wiley & Sons, Inc.