Synthesis and gas permeation properties of various Si-containing poly(diarylacetylene)s and their desilylated membranes

Abstract

Diarylacetylene monomers having trimethylsilyl groups and other substituents (substituted biphenyl, 1a and 1b; trimethylsilylmethylphenyl, 1c– e) were synthesized and polymerized with TaCl 5- n-Bu 4Sn catalyst to produce the corresponding poly(diarylacetylene)s ( 2a– d). Polymers 2a– c had high molecular weights and were soluble in common organic solvents. Free-standing membranes of 2a– c as well as previously reported 2f– h were prepared by the solution-casting method. Desilylation of these Si-containing polymer membranes was carried out with trifluoroacetic acid to afford 3a, 3b, and 3f– h. Upon desilylation, biphenyl-containing membranes became less permeable ( 3a, b), whereas fluorene-containing membranes became more permeable ( 3f– h). In particular, 3h exhibited extremely high gas permeability ( PO 2 = 9800 barrers), which is about the same as that of poly(1-trimethylsilyl-1-propyne). Desilylated membranes 3a and 3f– h showed different gas permeability from that of polymers 2i– k which have the identical chemical structures and obtained directly by the polymerization of the corresponding monomers.