Synthesis and Properties of Si-Containing Poly(diarylacetylene)s and Their Desilylated Polymer Membranes

The polymerization of 1-[( p -trimethylsilyl)phenyl]-2-(2-fluorenyl)acetylene ( 1c ) with TaCl 5 − n -Bu 4 Sn produced a high molecular weight polymer ( 2c ), whose M w reached 3.4 × 10 6 . 1-[( p -Trimethylsilyl)phenyl]-2-(2-phenanthryl)acetylene ( 1d ) and 1-[( p -trimethylsilyl)phenyl]-2-(4-biphenyl)acetylene ( 1e ) were also polymerized to give high molecular weight polymers ( 2d and 2e ) in good yields. In contrast, the polymerization of 1-[( p -trimethylsilyl)phenyl]-2-(2-anthryl)acetylene ( 1f ) provided no polymer probably owing to the steric reason. The formed polymers 2c and 2d were soluble in common solvents such as toluene and chloroform and afforded free-standing membranes by casting from toluene solution. The onset temperatures of weight loss of polymers 2c and 2d in air were about 430 °C, indicating very high thermal stability. The membranes of 2c and 2d obtained by the casting method showed high gas permeability; e.g., their oxygen permeability coefficients ( P O 2 ) were 1650 and 460 barrers, respectively. The membranes of 2c and 2d were desilylated with trifluoroacetic acid to provide the membranes of poly[1-phenyl-2-(2-fluorenyl)acetylene] ( 3c ) and poly[1-phenyl-2-(2-phenanthryl)acetylene] ( 3d ). The desilylated poly(diarylacetylene)s exhibited even higher P O 2 values of 2150 and 1300 barrers, respectively. These desilylated polymers were insoluble in any solvents and showed higher thermal stability than those of 2c and 2d .