Highly soluble phenylethynyl-terminated imides derived from mellophanic dianhydride (MPDA)

Novel highly soluble phenylethynyl-endcapped oligoimides with different calculated molecular weights were prepared by using mellophanic dianhydride and bis(4-amino-2-trifluoromethylphenyl)ether in the presence of 4-phenylethynyl phthalic anhydride as the reactive endcapping agent. The effect of molecular weights of the aromatic oligoimides on their solubility and processability as well as the thermal and mechanical properties of the thermal-cured polyimides was fully investigated. This kind of phenylethynyl-terminated imides exhibited excellent comprehensive properties. Most importantly, a big progress has been made in the solubility of the oligoimides in this paper. Most of the oligoimides showed excellent solubility (more than 33 wt%) even in acetone , which was reported for the first time. And oligoimides with appropriate molecular weights also showed very good processability with minimum melt viscosities no higher than 120 Pa·s by the rheological study. After thermally curing at 370°C for 1 hour, the cured flexible films showed very high glass transition temperatures up to 392°C by dynamic mechanical analysis, and the temperature of 5% weight loss was higher than 500°C in both air and N 2 atmosphere by thermogravimetric analysis. The cured films also exhibited very good toughness with elongation up to 9%.