The present invention relates to a method of preparing polycarbonate comprising the steps of: (i) introducing to an extruder through a feed port a plurality of reaction components comprising a polycarbonate oligomer, an activated carbonate residue, and a transesterification catalyst, wherein the extruder comprises the feed port, a first back vent port, and a polycarbonate exit port, wherein the feed port is located between the first back vent port and the polycarbonate exit port, and wherein the resistance to flow of the reaction components from the feed port to the first back vent port is less than or equal to the resistance to flow of the reaction components from the feed port to the polycarbonate exit port; and (ii) extruding the reaction components at one or more temperatures in a range between 100.degree. C. and 400.degree. C., wherein during the extrusion of the reaction components, activated carbonate residue is removed through the first back vent port, thereby preparing a polycarbonate.