The present work presents results on the copolymerization kinetics of methyl methacrylate (MMA) and vinyl chloride (VCM) monitored by Raman spectroscopy and on the evolution of droplets as captured by charge-coupled device (CCD) camera in a microcapillary reactor. Different experimental recipes were proposed using commercial initiators in order to compare the system performance when initiated with monofunctional and bifunctional peroxides. The experimental setup was able to capture the distinct stages of the copolymerization within a microreactor up to high conversions (>90%) in quiescent state. It is shown that the copolymerization of MMA with VCM leads to distinct morphological structures, when compared to VCM homopolymerization, forming a core and a shell after a certain critical conversion. A new mechanism is proposed for the copolymerization based on the results from both video camera and Raman spectroscopy. (C) 2017 Elsevier Ltd. All rights reserved.