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The solid‐state synthesis and properties are reported for a new polydiacetylene: poly[1,6‐di(N‐carbazolyl)‐2,4‐hexadiyne]. The monomer crystals polymerize quantitatively with γ irradiation or thermal annealing. An Autocatalytic effect is observed in both γ‐ray polymerization and thermal polymerization and is attributed to an increase in chain propagation length at about 5% conversion. The activation energy for thermal polymerization is about 25 kcal/mole, independent of the degree of conversion to polymer. The exceptional thermal stability of the polymer crystals allowed a thermomechanical analysis over a large temperature range, −50 to 300°C. With increasing temperature, the polymer contracts in the chain direction linearly with temperature over the entire range, yielding a thermal expansion coefficient of (−2.32 ± 0.02) × 10−5°C−1. Photoconductivity action spectra are reported for the polymer crystals. The energies for the photoconductivity onset (ca. 2.3 eV) and for the lowest energy optical transition (1.89 eV) are the lowest reported for the polydiacetylenes. The photoconduction onset is blue‐shifted with respect to optical absorption—a result which is consistent with the excitonic assignment for the lowest energy optical transition in the polydiacetylenes.

The extent of π electron delocalization in solid-state polymerized diacetylenes is derived from observed Raman vibrational frequencies. Raman intense C=C and C≡C vibrations indicate that the polymer backbone is best represented by (=C–C≡C–C=)n. However, vC=C is linearly correlated with vC≡C over a wide frequency range and both frequencies increase with decreasing phase perfection. This suggests a significant fractional contribution δ from the mesomeric structure (–C=C=C=C–)n, which decreases the π bond order of C=C to 1-δ and C≡C to 2-δ. Both vC=C and vC≡C are calculated as a function of δ and compared with observed frequencies for variously substituted polydiacetylenes in different physical states. Resulting ΔvC=C/ΔvC≡C values obtained using two different bond-length to bond-order approximations are in good agreement with the observed value (1.19±0.12).

Eckhardt, H.; Eckhardt, Craig J.; and Yee, K.C., "Thermal effects on the optical spectra of a polydiacetylene: Poly{1,2-bis [4-(isopropylcarbamoyloxy) -n-butyl]-1-buten-3-ynylene}" (1979). Craig J. Eckhardt Publications. 36.

The polymerization of the cyclic tetradiyne monomer, [(CH2) 2CCCC(CH2)2]4, containing interstitial chloroform has been investigated using Raman and Fourier‐transform infrared spectroscopy and x‐ray diffraction techniques. A loss of crystallographic register between chains occurs during the polymerization reaction, although crystalline order in the chain‐axis projection is retained. These studies indicate that 50 Mrad of 60Co γ‐ray irradiation produces 1,4‐addition polymerization at most of the diacetylene functionalities. Unreacted diacetylene groups are present primarily, although not completely, in soluble oligomeric material. Infrared spectroscopy indicates that this low molecular weight material has a butatriene (cumulene) backbone structure rather than the acetylenic structure of the insoluble polymer.