A single molecular catalyst system supported on MgCl2 has been developed and combined with a simple two-stage fed-batch polymerization process to produce tailored bimodal polyethylene reactor blend particles of UHMWPE. By varying and controlling the process conditions in the first stage and second stage, bimodal HMWPE:UHMWPE reactor particles are obtained with independent control over the individual molar masses, the mass ratio of the HMWPE and UHMWPE components, and the reactor powder particle size. This allows multidimensional control over the individual UHMWPE reactor particle properties. (c) 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1645-1656