The symmetric diacetylenes, 2,4-hexadiynylene dibenzoate 4 and 2,4-hexadiynylene bis(pentafluorobenzoate) 5, as well as the unsymmetric 6-(pentafluorobenzoyloxy)hexa-2,4-diynyl benzoate 6 were prepared and investigated with respect to their reactivity toward topochemical polymerization in the crystalline state. The 1:1 cocrystal 4-5 was successfully polymerized to the corresponding poly(diacetylene) copolymer 7, as evidenced by solid-state C-13 NMR and Raman spectroscopy, as well as single-crystal structure analysis of the monomer-polymer cocrystal. Thus, perfluorophenyl-phenyl interactions were utilized as complementary supramolecular synthons in the cocrystallization of two different diacetylene monomers and their unprecedented conversion into a strictly alternating diacetylene copolymer.