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Long chain branched bisphenol A polycarbonates (BA PC's) were prepared by use of a combination of thermally reactive 4-hydroxybenzocyclobutene (BCB-OH) and the nonreactive p-tert-butylphenol (PTBP) chain terminators. These two monophenols react under interfacial conditions at similar rates to provide a statistical distribution of coterminated PC's having molecular weights controlled by the total amount of coterminators. Heating these materials to 300 °C causes branching and/or cross-linking depending on the value of X BCB , thereby separating the polycondensation and branching processes and allowing greater degrees of branching than possible by random branching during polycondensation. At X BCB ∼2M e are relatively tough and flexible, while those having lower M n 'S, regardless of M w , are relatively brittle. The melt viscosities of branched BCB-OH/PTBP PC's are very high at low shear rates, as expected from their high M w 'S, but decrease dramatically with increasing shear rates to values approaching those of conventional linear and randomly branched PC's. Such high zero-shear viscosity, which is indicative of high melt strength, and large shear sensitivity suggests that these new materials could display significant improvements in melt processing by techniques such as blow molding, thermoforming, injection molding, and extrusion.