Synthesis of a series of asymmetrically substituted diacetylenes containing a thienyl moiety or a quinolyl moiety as one of the side groups directly bound to diacetylene and a urethane group as the other one was carried out. Though some of the prepared diacetylenes could be polymerized in solid state by using UV and gamma-radiation, all of them were stable when heat was used as the stimulus. The monomer to polymer conversion for the polymerizable ones was found to be in the range 35-60%. Various spectroscopic techniques, such as FTIR, solid state C-13 NMR and visible absorption spectroscopies, and powder X-ray diffraction were used to elucidate the structures of the polydiacetylenes. One of the polymers containing quinolyl moiety as directly bound side group showed unusually long and sharp absorption maximum indicating long and uniform conjugated chains. Third-order nonlinear optical susceptibility, chi((3)), Of two Of the polymers were measured using Maker＇s fringe technique. The largest value for chi((3)) in the resonant region for polymer backbone direction in single crystalline form was estimated to be on the order of 10(-11) esu.