Exceptional high gas permeability and physical aging resistance of silyl-functionalized fluorene-based poly(substituted acetylene)s

Poly(substituted acetylene)s have emerged as highly promising materials for gas-permeable membranes in gas separation systems. A novel series of silyl-functionalized fluorene-based poly(substituted acetylene)s ( Copoly(Flu1-Flu2) s) were synthesized via copolymerization of 1-phenyl-2-(7-trimethylsilyl-9,9-bistrimethylsilylfluoren-2-yl)acetylene ( Flu1 ) with 1-phenyl-2-(7-trimethylsilyl-9,9-dimethylfluoren-2-yl)acetylene ( Flu2 ). Solution-cast copolymer membranes exhibited exceptional gas permeabilities, with the Copoly(Flu1-Flu2)(4:1) membrane showing oxygen ( P O2 = 19,800 Barrer) permeability that surpass those of homopolymers. Desilylation via trifluoroacetic acid treatment altered permeability depending on the feed ratio, attributed to competitive effects of chain packing densification and microvoid generation. XRD and N 2 adsorption analyses revealed that higher Flu1 content increased chain spacing ( d -spacing = 15.2 Å) and BET surface area (492 m 2 /g), with desilylation inducing pore structure reorganization. The membranes exhibited good thermal stability ( T d > 420 °C) and resistance to physical aging ( P O2 reduction < 10% within 240 days), underscoring their potential for gas separation applications. • Silyl-functionalized fluorene copolymers exhibit ultrahigh gas permeability • Copoly(Flu1-Flu2)(4:1) achieves P O2 of 19,800 Barrer with low density (0.790 g/cm 3 ) • Desilylation inflects microporosity via removal of bulky SiMe 3 groups • Controlled copolymerization and desilylation optimize chain packingand porosity • Less than 10% P O2 loss after 240 days demonstrates strong physical aging resistance