Synthesis and characterization of new organosoluble and gas-permeable polyimides from bulky substituted pyromellitic dianhydrides

Two new pyromellitic dianhydrides, 1,4-bis(4'-t-butylphenyl) pyromellitic dianhydride and 1,4-bis(4'-trimethylsilylphenyl) pyromellitic dianhydride, were synthesized via Suzuki coupling, oxidation, and dehydration. A series of new organosoluble polyimides were prepared from the obtained pyromellitic dianhydride and various aromatic diamines by the conventional polycondensation reaction followed by chemical imidization, as well as high-temperature, one-step polymerization. The structures of the dianhydrides and polymers were identified with various spectroscopies. The inherent viscosities of the resulting polymers were 0.62-1.89 dL/g. The synthesized polyimides showed good solubility in various organic solvents such as N-methyl-2-pyrrolidinone, N,N-dimethylacetamide, and p-chlorophenol. These polymers had glass-transition temperatures of 230-260 degreesC. Thermogravimetric analysis showed that all the polymers were stable, with 10% weight losses recorded above 490 degreesC in nitrogen. The polyimide films had good mechanical properties and high oxygen permselectivity to nitrogen. The oxygen permeability coefficient (P-O2) and the permselectivity of oxygen to nitrogen (P-O2/P-N2) of the films were 13-56 barrer and 3.7-5.5, respectively. (C) 2002 Wiley Periodicals, Inc.