Formation of Bundle Assemblies of Stereoregular Polymers in Thermal Solid-State Polymerization of 7,7,8,8-Tetrakis(aryloxycarbonyl)‑p‑quinodimethanes
7,7,8,8-Tetrakis(aryloxycarbonyl)-p-quinodimethanes with bulky aryloxy groups such as benzyloxy
(1a), pentafluorobenzyloxy (1b), and
both benzyloxy and pentafluorobenzyloxy (1c) were
synthesized. We investigated effects of these bulky groups on thermal
solid-state polymerization reactivities on the basis of crystal structures
of 1a–1c. Thermal polymerizations
gave 1,6-trans-type stereoregular polymers in quantitative
yields in 1 day at 110 °C for 1a, 1 day at 150 °C
for 1b, and 6 days at 110 °C for 1c. Their initial crystal shapes were retained in appearance during
polymerization to yield solid bundle assemblies of their polymeric
chains. X-ray single-crystal structure analysis indicates that their
crystals adopt molecular arrangements suitable for one-dimensional
polymerization with the 1,6-trans-type addition along
one crystallographic axis. Such arrangements led to expansion polymerization
of 1b and contraction one of 1c. The resulting
stereoregular polymers form less ordered bundle assemblies than those
prepared by the conventional topochemical polymerization. In this
manner, the bulky aryloxy groups enabled us to observe a close relation
between the molecular assembly modes and the polymerization behaviors,
providing the first example for proving diversity of thermal solid-state
polymerizations.