A synthetic strategy is presented that allows the preparation of dimethylamino functionalized. heterocyclic system 1,3-di (p-dimethylaminobenzyl)-imidazolidine-2-thion that was then used to prepare polyimides by the two-stage polycondensation method. The key to this success was the development of an efficient procedure leading highly pure dimethylamino monomer. Polyimides derived from 1,3-di(p-dimethylaminobenzyl)-inmidazolidine-2-thion and commercial dianhydrides exhibited excellent solubility in various polar solvents. These polymers showed glass transition temperatures between 290-360degreesC, and initial decomposition temperature 490-485 degreesC and 10% mass loss ranging from 505-575degreesC in air.