Solid‐state synthesis of a ladder polymer

Solid‐state synthesis of a cyclically bound ladder polymer from a cyclic tetradiyne (cyclodotriaconta‐1,3,9,11,17,19,25,27‐octayne) is described. Irradiation of the colorless, needlelike monomer crystals with interstitially incorporated chloroform with 50 Mrad of 60Co γ‐ray radiation results in red‐brown polymer fibers in nearly quantitative yield. Infrared, Raman, and x‐ray diffraction analyses of the polymer are consistent with polymerization by a 1,4‐addition reaction at each diacetylene linkage to produce four fully conjugated chains joined together in pairs by a total of four (CH2)4 interchain linkages per 4.8‐Å polymer repeat unit. Conformationally, it appears that the cyclic tetradiyne monomer polymerizes via a chair form. The results of the mechanical and thermal analyses indicate the presence of unreacted diacetylene functionality in the ladder polymer crystals.