Two series of new poly(amide imide)s having (n-alkyoxy)phenyloxy side branches with various lengths, poly[p-phenyleneiminoterephthaloylimino-p-phenylene[3,6-di(n-alkyloxy)phenyloxylpyromellitimide)s (PCmTAs, m = 4, 8, 12) and poly{p-phenyleneiminosebacoylimino-p-phenylene[3,6-di(n-alkyloxy)-phenyloxy]pyromellitimide}s (PCmSeAs, m = 4, 8, 12), were prepared by condensation of terephthalamide-N,N'-4,4'-dianiline (TA) and sebacamide-N,N'-4,4'-dianiline (SeA) with 3,6-di[4-(n-alkyloxy)phenyloxy]pyromellitic dianhydrides, respectively. The inherent viscosities of the polymers were in the 0.82-1.20 dL/g range. The polymers were highly soluble in N-methylpyrolidinone (NMP), even at room temperature and soluble in other polar aprotic solvents on heating. The PCmTAs, which have aromatic backbones, were thermally more stable (431-442 degreesC) than the PCmSeAs, which have an octamethylene unit in the main chain (407-409 degreesC). Degradation of weight up to 900 degreesC corresponded with the loss of side chain contents. The PCmAs exhibited no phase transition, whereas two endothermic peaks were observed for each of the PCmSeAs. Wide-angle X-ray diffractometer investigations revealed that both polymers are amorphous and the n-alkyloxy side chains are present in a layered structure.