Solid-state polymerization of phenylbutadiyne derivatives with o-nitro, m-nitro or p-nitro group was investigated. All monomers in bulk crystals could be thermally polymerized to become black suggesting formation of extended p-conjugation system. However, no regular polydiacetylene structures were confirmed by the structural analysis. Nanocrystals of the m-nitro derivative were prepared, and the different polymerization behavior compared with in the bulk crystals was observed.