Unsymmetrica11y substituted diacety1enes (1–5) with a mesogenic core on one side were prepared. As a substituent on the other side was introduced para-substituted benzenesulfonyl group, which is a substituent of symmetrically substituted diacetylenes PTS and PCS. Both diacetylene monomers1and2. were found to polymerize by heating in solid state with a similar reactivity, which shows a sharp contrast to a large difference in reactivity between PTS and PCS. Hydroxymethyl derivative3polymerized in both crystal state and liquid crystal state. Characteristic reaction behavior of3in a nematic phase was elucidated. Other examples of reactive unsymmetrical monomers are presented.