Synthesis and Properties of Poly(diphenylacetylenes) Having Hydroxyl Groups

Polymerization of several diphenylacetylene derivatives was carried out by using TaCl 5 − n -Bu 4 Sn as catalyst. C 6 H 5 C≡CC 6 H 4 - p -OSi(CH 3 ) 2 t -Bu ( 3a ) and C 6 H 5 C≡CC 6 H 4 - m -OSi(CH 3 ) 2 t -Bu ( 3b ) provided the corresponding polymers (poly( 3a ), poly( 3b )) with high molecular weights in good yields, while p - t -Bu(CH 3 ) 2 SiOC 6 H 4 C≡CC 6 H 4 - p -OSi(CH 3 ) 2 t -Bu ( 3c ), p - t -Bu(CH 3 ) 2 SiOC 6 H 4 C≡CC 6 H 4 - m -OSi(CH 3 ) 2 t -Bu ( 3d ), and m - t -Bu(CH 3 ) 2 SiOC 6 H 4 C≡CC 6 H 4 - m -OSi(CH 3 ) 2 t -Bu ( 3e ) did not satisfactorily. Desilylation of poly( 3a ) and poly( 3b ) membranes catalyzed by trifluoroacetic acid yielded poly(diphenylacetylenes) having free hydroxyl groups [poly( 4a ), poly( 4b )], which are the first examples of highly polar group-carrying poly(diphenylacetylenes). Poly( 3a ) and poly( 3b ) dissolved in nonpolar solvents such as toluene and chloroform, while poly( 4a ) and poly( 4b ) were insoluble in these solvents. According to TGA in air, poly( 3a ) and poly( 3b ) were thermally fairly stable among substituted polyacetylenes, and poly( 4a ) and poly( 4b ) displayed even higher thermal stability. The P CO 2 / P CH 4 and P CO 2 / P N 2 permselectivity ratios of poly( 4a ) and poly( 4b ) membranes were as large as 13−46, while keeping relatively high P CO 2 values.