Host-Guest Approach for 1,6-Topochemical Polymerization of Triacetylenes

Abstract

Since Shirakawa et al. discovered the promising electrical conductivity of polyacetylene in the 1970s, polyacetylenes and their analogous have been extensively explored as advanced materials. Among them, polytriacetylenes are a new class of conjugated polymers that can only be achieved by topochemical polymerization. Theoretically, topochemically polymerizing the triacetylene monomers is the most direct route to get polytriacetylene. However, the challenge in 1,6 polymerization is to get the suitable molecular spacing for the topochemical reaction. Host-guest strategy was developed to achieve the specific spacing suitable for topochemical polymerizations, such as 1,4 and 1,6- polymerizations. After optimizing the previous synthesis route and crystal growing method, a quality co-crystals of 3-((3-(pyridin-4-yl)propyl)amino)cyclohex-2-enone and dodeca-4,6,8-triynedioic acid was successfully prepared. The co-crystal, with repeat distance of 7.25 ? , underwent a 100% polymerization at 115 degrees C over 19days. X-ray diffraction was used to characterize all monomer and polymer crystals. Another attempt has been made to design and synthesize a triacetylenes that assembled due to pi-pi interaction. This pyridyl-substituted triacetylene was successfully synthesized in a five-step route. X-ray diffraction was utilized to characterize the single crystal of octa-2,4,6-triyne-1,8-diyl dinicotinate which indicated the repeat distance of 7.408 ? . This value meets the ideal requirement for 1,6- polymerization.