Three-arm poly (epsilon-caprolactone, reactive extruded) (REX-PCL) polymer was continuously produced using a twin-screw extruder with aluminum tri-sec butoxide (ATSB) initiator in residence times of less than five minutes. Monomer conversions in excess of 95% were achieved, and high molecular weight PCL was produced. The number average molecular weight of each arm of REX-PCL ranged from 30,000 to 200,000 g/mol. A screw configuration comprising entirely of conveying elements was most effective in the extrusion polymerization process. The REX-PCL polymer was characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and intrinsic viscosity measurements.