The dimer, trimer, and tetramer of 1,11-dodecadiyne, HC=C-(CH2)(8)-C=CH, were synthesized. The solid-state polymerization of the dimer was investigated by infrared (IR) spectroscopy. IR bands due to the diacetylene moiety were identified through the comparison of the IR spectra of the dimer, trimer, and tetramer. The dimer was found to have two polymorphs, melt-crystallized and solution-crystallized. Both of the polymorphs undergo solid-state polymerization by exposure to gamma-ray or UV irradiation. The former has higher polymerizability for the diacetylene moiety than the latter. The solid-state polymerization of the terminal acetylene group was not observed. It is shown that the previously reported dimer structure in which both the diacetylene and terminal acetylene groups are polymerized to form an inherently electrically conducting polymer is incorrect.