Preparation and properties of two-legged ladder polymers based on polydiacetylenes

A novel diacetylene derivative, N,N'-bis[5-(3-tolylaminocarbonyloxy)-1,3-pentadiynyl]-N,N'-diphenyl-1,4- phenylenediamine (1), was prepared, where two diacetylene groups were connected by a 1,4-phenylenediamine moiety. The molecules stacked one-dimensionally and showed solid-state-polymerization reactivity above 80 degrees C. The decay of the monomers at 100 degrees C proceeded gradually without a marked induction period and was fully completed after 400 h. The obtained polymer was a crystalline solid judged by powder X-ray diffraction (PXRD) patterns and SEM imaging. The conjugated pi-system of the obtained polymer was classified as a two-legged conjugated ladder. The polymer showed a broad absorption from the visible to the near IR region, indicating a decrease in the optical band gap of ca. 1.0 eV, because of the expansion of the pi-conjugated system from a one-dimensional system to a ladder. The ladder polymer showed high conductivity after I(2) doping from sigma(293K) = 5 x 10(-12) S cm(-1) to 1.2 x 10(-5) S cm(-1). The conductivity depended heavily on the pressure of iodine and reached s373K 2.3 x 10(-1) S cm(-1). The activation energy of the ladder polymer was also estimated as 360 meV.