Semi-conducting cyclic copolymers of acetylene and propyne

Polyacetylene (PA) exhibits conductivities comparable to metals after doping, yet the extremely low solubility of PA limits its processing and utility. Introducing pendent groups can alter the properties of PA. Copolymerizing acetylene and propyne using Zieglar-Natta type catalysts affords linear poly(acetylene-co-propyne) as free-standing films. However, this process requires grams of catalysts and extensive workup. Cyclic polyacetylene is a unique topological isomer of linear polyacetylene. Herein, we report a facile synthesis of cyclic poly(acetylene-co-propyne) as thin, flexible films with extremely low catalyst loading (milligrams) and easy purification. Altering the feed ratio of acetylene and propyne produces copolymers with different acetylene/propyne incorporations. The films exhibit similar conductivities as linear copolymers after doping. The soluble portions of different cyclic copolymers exhibit low acetylene incorporation. TGA analysis reveals the cyclic copolymers are less thermally stable than cyclic PA, with the stability dependent on the ratio of acetylene and propyne incorporation. [Display omitted] •Semiconducting cyclic copolymer synthesis.•Lustrous free standing films of cyclic polymer.•Low catalysts loading and efficient synthesis of semiconducting polymer.•Gaseous synthesis of semi-conducting cyclic copolymer.