Synthesis and Properties of Poly(diphenylacetylenes) Having Hydroxyl Groups

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