Abstract: The present invention provides a preparation method of polyimide, comprising the following steps: a) carrying out a dehydration polymerization reaction on a diamine and an anhydride of an organic acid in a non-polar solvent to obtain a mixture, the non-polar solvent being one or more of arene, aliphatic hydrocarbon, halogenated arene and halogenated aliphatic hydrocarbon, and the anhydride of the organic acid being one or more of dianhydride and single anhydride: and b) filtering the mixture obtained in step a) and drying to obtain the polyimide. In the present invention, the dehydration polymerization reaction between the diamine and the anhydride of the organic acid can be carried out directly in the non-polar solvent to obtain the polyimide which cannot be dissolved in the non-polar solvent. Therefore, polyimide powder with fine particles can be obtained by directly filtering and drying the reaction mixture without washing.

Abstract: Polythioetherimides and a producing method thereof. The method is comprised of using monosubstituted phthalic anhydride isomer as raw material, reacting it with disubstituted amine to produce disubstituted phthalimide, allowing coupling reaction between the obtained phthalimide and an alkali metal sulfide or sulfur to produce polythioetherimides.