Effect of methyl group on gas permeability of trimethylsilyl-containing poly(diphenylacetylene)s

Abstract

Novel highly gas-permeable diphenylacetylene polymers ( P1 – P4 ) were synthesized via polymerization of diphenylacetylenes bearing a methyl group directly beside the trimethylsilyl group ( p -Me 3 Si- m -MeC 6 H 3 C CC 6 H 4 R; R = H ( 1 ), p -SiMe 3 ( 2 ), p - t -Bu ( 3 ), and m -SiMe 3 ( 4 )). The corresponding polymers P1 and P4 were completely soluble in various organic solvents, whereas polymers P2 and P3 were insoluble. Polymer P1 exhibited a very high oxygen permeability coefficient ( P O2 ) of 3960 barrers, indicating that the methyl groups had a profound effect on the gas permeability. Polymer DP1 , obtained by the desilylation of P1 , exhibited even higher gas permeability. The copolymerization of 2 and 3 with 1 yielded solvent-soluble high-molecular-weight copolymers ( P12 and P13 ) with very high gas permeabilities. The methyl groups were found to broaden polymer chain distance. The gas permeabilities of P12 and P13 increased and decreased, respectively after desilylation. Although the oxygen permeability of the polymers/copolymers gradually decreased with storage time, their P O2 remained high (2220–4140 barrers) even after 90 days. • Novel highly gas-permeable methyl group-bearing poly (diphenylacetylene) polymers. • Inclusion of methyl group at meta position increased the gas permeability. • Highest P O2 = 3960 barrers for hompolymer and P O2 = 5540 barrers for copolymer. • Desilylation further enhanced the gas permeability ( P O2 ≤ 7830 barrers). • High gas permeability ( P O2 = 2220–4140 barrers) even after 90 days.