SYNTHESIS OF AROMATIC POLYMERS VIA PALLADIUM-CATALYZED CROSS-COUPLING REACTIONS WITH MAGNESIUM, ZINC, AND TIN REAGENTS - A COMPARISON

Difunctional magnesium, zinc, and tin reagents M - C6H4 - O - C6H4 - M (M = MgBr, ZnCl, SnBu3) in the presence of palladium or nickel catalysts undergo cross-coupling polymerizations with aromatic, heteroaromatic, benzylic, and allylic dihalides to give oligomeric and polymeric materials. Tin reagents lead to products of higher molecular weight than Mg and Zn reagents. The reaction is sensitive to the solvent and enhanced by magnesium halides. Increased reaction temperatures lead only to moderate increases in the degree of polymerization and are limited by catalyst decomposition above 200-degrees-C. The new poly(ether ketone) and poly(ether sulfone) type polymers prepared show high thermal stability. In contrast to conventional poly (ether sulfones) s, the biphenyl-based sulfone polymers reported here are crystalline.