Synthesis and Properties of F-Containing Poly(diphenylacetylene) Membranes

The polymerization of various silyl- and F-containing diphenylacetylenes ( 1 a − k ) with TaCl 5 − n -Bu 4 Sn provided high-molecular-weight polymers. Most polymers ( 2 a − d, 2g, and 2h ) were totally soluble in common organic solvents and afforded tough free-standing membranes by casting from toluene solution, while some polymers ( 2e, 2f, and 2i − k ) were insoluble in any organic solvents. The onset temperatures of weight loss of polymers 2 a − d in air were over 400 °C, indicating very high thermal stability. The membranes of 2 a − d were desilylated with trifluoroacetic acid to give desilylated polymer membranes 3 a − d, which were insoluble in any solvents. The fractional free volumes (FFV) of the present membrane-forming trimethylsilyl and/or F-bearing polymers ( 2 a − d and 3 a − d ) were ca. 0.28−0.31 and appreciably large, and they showed very high permeability (ca. 1400−14 000 barrers) to the six gases examined. The oxygen permeability coefficient ( P O 2 ) of 2a was as high as 2900 barrers, which is about twice that of poly[1-( p -trimethylsilyl)phenyl-2-phenylacetylene]. The incorporation of F atoms into both poly[1-( p -trimethylsilyl)phenyl-2-phenylacetylene] and poly(diphenylacetylene) generally enhanced gas permeability.