Synthesis and Properties of Membranes of Poly(diphenylacetylenes) Having Fluorines and Hydroxyl Groups

Diphenylacetylenes possessing fluorine atom(s) and a siloxy group ( 1c − i ) were polymerized with TaCl 5 − n -Bu 4 Sn. Monomers 1c − f having a siloxy group at the para position of a phenyl ring produced high molecular weight polymers ( 2c − f ) in good yields. These polymers afforded tough free-standing membranes by casting their toluene solution. Desilylation of the polymer membranes was carried out with trifluoroacetic acid to give membranes of poly(diphenylacetylenes) having fluorine atoms and hydroxyl groups ( 3c − f ). Polymers 2c − f were soluble in various organic solvents such as toluene, CHCl 3, and THF, while polymers 3c − f were insoluble in these solvents. All the polymers 2c − f and 3c − f exhibited high thermal stability. The gas permeability of most membranes in the present study ( 2d − f and 3c − f ) were higher than those of the corresponding polymers without fluorine atoms ( 2a and 3a ), indicating that incorporation of fluorine atoms into the polymers enhances gas permeability. The P CO 2 / P N 2 permselectivity ratios of polymers 3c − f were as large as 36−48, and the points of 3c − f in the P CO 2 vs P CO 2 / P N 2 plot were located above Robeson's upper bound.