Synthesis and properties of indan-based polyacetylenes that feature the highest gas permeability among all the existing polymers

Acetylenic monomers containing indan and other groups (1a-m) were polymerized with TaCl₅-n-Bu₄Sn catalyst to give high molecular weight polymers. Most polymers were soluble in common organic solvents including toluene and chloroform, and they afforded free-standing membranes by the solution casting method The onset temperature of weight loss of the polymers were over 400 °C, indicating high thermal stability. Despite the absence of bulky spherical groups, polymethylated indan-containing polymer membranes showed extremely high gas permeability. In particular, the oxygen permeability coefficients of polymers having 1,1,3,3-tetramethylindan and either p-fluorophenyl or p,m-difluorophenyl groups (2b and 2e) reached 17 900 and 18 700 barrers, respectively, which are even larger than that of the most permeable polymer known, poly(1-trimefhylsilyl-1-propyne)