Dynamic optimization of a continuous polymer reactor aims to decide optimal trajectories of control input variables so that the transition time, required to reach the desired steady state from the initial state during startup or grade-change operation, is minimized. The problem is challenging because of its highly nonlinear dynamics and multimodal properties. The proposed modified differential evolution (MDE) algorithm is different from differential evolution algorithms in the sense that MDE employs a local search to enhance the computational efficiency and modified heuristic constraints to systematically reduce the size of the search space. The algorithm is illustrated by several case studies using the dynamic optimization problem of a continuous methyl methacrylate-vinyl acetate copolymerization reactor. The case studies have shown that the proposed algorithm offers faster speed, flexible implementation, and higher robustness to find the global optimum than differential evolution algorithms.