sieves next to a three necked bottle 500 ml poe2000 100 g 0 05 mol is added and dissolved in thf 150 ml and then anhydride linker tma 19 2 g 0 10 mol previously dissolved in thf 50 ml is added drop by drop so that molar ratio of poe2000 to tma is 1 2 the reactant is mechanically stirred and filled with nitrogen during the whole reaction the reaction is performed at 30 u00b0 c for 2 hours or longer ft ir spectrum is used for monitoring progress of the reaction by sampling every period of time until the anhydride functional groups disappear after the reaction is completed thf is removed by decompression to obtain creamy glue product amido acid poe2000 tma 4cooh to a three necked bottle the stabilizer poe2000 4cooh 0 069 g is dissolved in water 50 g which is stirred with a magnetic stirrer agno 3 0 045 g is then added later after 2 hours a nabh 4 solution 0 015 g previously dissolved in water 50 g is added incontinuously and vigorously agitated the solution immediately becomes black the reactor is filled with nitrogen during whole reaction the product poe2000 4cooh of example 1 is heated at 150 u00b0 c for 3 hours progress of the reaction is monitored with ft ir for identifying imido functional groups the product is imido acid poe2000 2cooh repeat step b of example 1 but the stabilizer is replaced with poe2000 2cooh repeat step a of example 1 but hydrophilic poe2000 is replaced with hydrophobic pop2000 to obtain product imido acid pop2000 4cooh repeat step b of example 1 but the stabilizer is replaced with poe2000 4cooh the product pop2000 4cooh of example 3 is heated at 150 u00b0 c for 3 hours progress.