Synthesis of Hyperbranched Polyphenylene with High Degree of Polymerization and 100% Degree of Branching from A2 + B3 Suzuki-Miyaura Polycondensation through Intramolecular Catalyst Transfer

Suzuki-Miyaura polycondensation of tribromobenzene and p-phenylenediboronic acid ester in the presence of tBu3PPd precatalyst afforded hyperbranched polyphenylene with 100% degree of branching and a much higher degree of polymerization than predicted by the Flory-Stockmayer theory. Based on the result of a model reaction of tribromobenzene with phenyboronic acid in the presence of the same Pd catalyst, this polymerization behavior is probably due to successive tri-substitution of tribromobenzene with the boronate in the monomer and oligomers through intramolecular Pd-catalyst transfer. Suzuki-Miyaura polycondensation of tribromobenzene and p-phenylenediboronic acid ester in the presence of tBu3PPd precatalyst afforded hyperbranched polyphenylene with 100% degree of branching and a much higher degree of polymerization than predicted by the Flory-Stockmayer theory. Based on the result of a model reaction, this polymerization behavior is due to successive tri-substitution of tribromobenzene with the boronate through intramolecular Pd-catalyst transfer.