Structures of the polymers obtained by solid-state polymerization of diyne, triyne, and tetraynes substituted by long chain alkyl groups were investigated by solid-state C-13 NMR spectroscopy. Assignment of all peaks in the spectra were made successfully, referring to those of the monomers and the polydiacetylenes of known structures. It was clearly shown that the backbone of these polymers has always the same structure of [GRAPHICS] This fact suggests that only 1,4-addition polymerization takes place in the similar way for the diyne, the triyne and the tetraynes, excluding many other possible addition schemes, and the tetraynes give an interesting polydiacetylene with butadiynyl substituents. This exclusive 1,4-addition can be explained in terms of topochemical control.