Diphenyl ether (DPE) and diphenyl ketone (DPK) are the molecular constituents of polymers such as PEK, poly(ether–ketone); PEEK, poly(ether–ether–ketone), and PEEKK, poly(ether–ether–ketone–ketone). A conformational analysis of DPE and DPK is examined by means of semiempirical calculations using CNDO/2 (Complete Neglect of Differential Overlap). The modelization is first run disregarding electronic interactions and steric effects, then introducing them in the calculations. We found that the absolute minimum energy conformer has torsional angles (θ1,θ2) = (30°,150°) for the DPE (with and without interactions) and (θ1,θ2) = (90°,90°) for the DPK (without interactions). Considering the polymer chains of PEK, PEEK, and PEEKK, the motion of DPE is expected to be easier than that of DPK in regions of local motions and for equivalent steric effects. Keywords: conformational analysis, diphenyl ether, diphenyl ketone, CNDO/2, rotational barriers.
