Particle size distributions of P(VAc-co-MMA) beads produced through nonconventional suspension copolymerizations II. Use of focused beam reflectance measurements for in-line monitoring of chord size distributions

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The use of polymer beads in biomedical applications has increased significantly over the past few years. In some of these applications, such as vascular embolization (VE), the control of particle size distributions (PSD) is of fundamental importance to assure safe and reproducible biomedical results. Particularly, polymer beads intended for biomedical applications are frequently produced through suspension polymerization processes, which can be monitored in-line with help of Focused Beam Reflectance Measurements (FBRM), which can provide chord size distributions (CSD) and PSDs in real time. For this reason, the FBRM technique is used here for the first time to monitor suspension polymerizations performed in semibatch mode and in the presence of small amounts of inhibitors, as these nonconventional suspension polymerization processes allow for production of polymer particles with narrower PSDs [1]. It is shown here that suitable combination of these nonconventional techniques may allow for faster stabilization of the CSDs of suspended particles, keeping the CSDs (and PSDs) approximately constant during longer periods of the batch time. The faster stabilization of rates of breakage and coalescence of suspended particles in the initial reaction trajectory probably explains the narrower PSDs of the final particles.