A new interesting class of polyamides containing diarylidenecyclopentanone moiety IIIa-f was synthesized by polycondensation reaction of the new diamino arylidene monomer I with different aliphatic and aromatic diacid chlorides (including adipoyl, sebacoyl, oxaloyl, terephthaloyl, isophthaloyl, biphenyldicarbonyl) and LiCl anhydrous as a catalyst at room temperature in NMP. The model compound II was synthesized by the interaction of one Mole of diarylidenecyclopentanone monomer I with two moles of benzoyl chloride in NMP/LiCl at room temperature. The structure of the model compound was confirmed by correct elemental and spectral analyses. The resulting polymers were characterized by elemental and spectral analyses, beside solubility and viscometry measurements. The thermal properties of those polymers were evaluated by TGA, DTG, and DTA measurements and correlated to their structural units. X-ray analysis showed that polymers having high degree of crystallinity in the region 20 = 5 - 60 degrees. In addition, the UV-visible spectra of some selected polymers were measured in DMSO solution and showed absorption bands in the range 260 - 475 11111, due to n - pi* and pi - pi* transition. On the other hand, the corrosion inhibition behavior of selected examples of polyamides was carried Out on carbon-steel in 0.5M H2SO4 at 40 degrees C. (c) 2009 Wiley Periodicals, Inc. I Appl Polym Sci 112: 513-523, 2009