The present invention relates to a process for preparing a poly(N-acylamide) by reaction between: —at least one compound of the following formula (I): X—R1—Y (I) and —at least one compound of the following formula (II): X′—R2—Y′ (II) in which: —R1 and R2 are, independently of one another, chosen from the group consisting of: a linear or branched alkylene group, comprising from 4 to 20 carbon atoms, an arylene group comprising from 5 to 30 carbon atoms, a heteroarylene group comprising from 5 to 30 atoms, a cycloalkylene group comprising from 5 to 30 carbon atoms, an arylalkylene group comprising from 5 to 30 carbon atoms.