Solid-state polymerization of derivatives of 2,4,6-octatriyne: 9. Topochemical reactions of monomers with conjugated triple bonds

The solid-state polymerization of monomers with three conjugated triple bonds gives rise to polymer single crystals. The lattice parameters of the polymers from 2,4,6-octatriyne-1,8-diol and 2,4,6-octatriyne-1,8-diol-bis(phenyl urethane) were determined. Based on these data and considering the mechanical properties and dichroism of the polymer crystals, it is concluded that polymerization proceeds according to a 1,4-addition to the triple bond system of the monomers. Only two of the three triple bonds of the monomers are affected by polymerization to form the polymer backbone of regularly alternating double, single and triple bonds. The residual triple bond is regularly arranged in the all-trans position as part of the substituents. The kinetics of the thermal and photopolymerization of these monomers are quite similar to those of the corresponding diynes. The activation energy of thermal polymerization was found to be 23 kcal/mol as compared to 19 kcal/mol for comparable diynes. The long wavelength limit of photosensitivity was found to be at about 380 nm as compared to 330 nm for diynes.