An investigation was carried out to improve polyimide processability via internal plasticization. This approach entailed the synthesis of a series of diamines in which the length of the alkyl group in alkyl 3,5-diaminobenzoates was varied from one to eighteen carbons. The polyimides obtained from several of these diamines were found to have increased solubility, a lower glass transition temperature and improved processability. Copolyimides were synthesized from 4,4’-oxydianiline, n-octadecyl 3,5-diaminobenzoate and 3,3’,4,4’-benzophenonetetracarboxylic dianhydride. It was found that incorporating only 10% of the plasticizing diamine improved processability sufficiently enough to allow moulding of the neat resin. This was in marked contrast to the parent polymer which was an insoluble and infusible polyimide.