Solid-state polymerization of conjugated hexayne derivatives with different end groups

Three hexayne derivatives with different end groups—that is, 10,12,14,16,18,20-triacontahexayne-1,30-diol (1) and its diphenylurethane (2) and diphenylester (3)—were synthesized, and their solid-state polymerization behaviors were investigated. All three monomers were thermally polymerizable. Polymers from 1 and 2 showed an absorption maximum at about 730 nm, indicating that linear polydiacetylenes (PDAs) with octatetraynyl substituents were synthesized. However, broad absorption bands in the near-infrared region were only observed for 2 at 980 and 860 nm, indicating that regular polymerization occurred in 2 to give ladder-type PDA. On the other hand, a polymer from 3 showed a visible absorption increase but no clear absorption maximum. It was estimated that intermolecular hydrogen bonding between hexayne monomers helps to form polymerizable stacks in 1 and 2. In particular, urethane groups are more effective, and 2 showed the highest reactivity in this study with an ordered interlayer structure even after a two-step solid-state polymerization to give ladder-type PDA. Polymer Journal (2010) 42, 201–207; doi:10.1038/pj.2009.326; published online 23 December 2009