The effect of solid-state polymerization on the crystal morphology of a type of polydiacetylene single crystal grown by the physical vapor transport technique was experimentally investigated by optical microscopy and atomic force microscopy. The formation of backbone chains along the [001] direction was unequivocally confirmed by our experimental results. The specific cleavage characteristics of the polydiacetylene single crystal were confirmed to be strongly affected by a morphological change due to solid-state polymerization. (C) 2013 Elsevier B. V. All rights reserved.