No abstract

A series of cardo poly(ether sulfone imide)s (PESI-C) containing bulky phthalide groups were prepared via aromatic nucleophilic substitution reaction of phenolphthalein with 4,4′-difluorodiphenyl sulfone and 4,4′-bis(4-fluorophthalimido)diphenyl ether (BFPI). The glass transition temperatures and 5% weight loss temperatures in nitrogen of the resulting PESI-C increased from 258°C to 278°C and from 468°C to 495°C with increasing the content of imide moiety in the polymer chain, respectively. These PESI-C films were transparent and essentially colorless and exhibited good mechanical properties with tensile strengths of 91–124 MPa, elongations at break of 6.9–12.8%, and tensile moduli of 2.2–2.8 GPa, respectively. It is noted that the tensile strengths, elongations at break, and tensile moduli of PESI-C also increased with increasing the content of BFPI in the copolymerization, indicating that the properties could be adjusted by controlling the ratio of BFPI and 4,4′-difluorodiphenyl sulfone.

A series of oligomers based on the mixture of thioetherdiphthalic anhydride isomers and 4,4 0 -oxydianiline with 4-phenylethynylphthalic anhydride as reactive endcapping reagent were prepared. The calculated molecular weights were in the range of 1150-5070 g mol À1 with different degrees of polymerization (n ¼ 1, 3, 5, 7, and 9). The effect of molecular weight of the aromatic oligomers on their processability and solubility as well as the thermal and mechanical properties of the thermal-cured polyimides (PIs) was systematically investigated. The typical oligomer (Oligo-1) could be melted at temperatures of 289-334 C to yield stable molten fluid with melt viscosity below 1.0 Pa s. The melt viscosity of the oligomers increased with the increasing molecular weight. After thermally curing at 370 C, the thermoset PIs exhibited good thermal properties. The glass transition temperatures of oligomers measured by differential scanning calorimetry were in the range of 286-326 C, and the temperature of 5% weight loss was higher than 524 C. The cured films also showed good mechanical properties with tensile strength above 72 MPa and modulus more than 2.5 GPa.