The kinetics of the early stage of dispersion polymerization in supercritical CO2 as monitored by turbidimetric measurements, 1. Method

• Published in: Macromolecular chemistry and physics 2000-09, Vol.201 (13), p.1532-1539
• Main Authors: Fehrenbacher, Ulrich, Muth, Oliver, Hirth, Thomas, Ballauff, Matthias
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Polymerization; Preparation, kinetics, thermodynamics, mechanism and catalysts
• ISSN: 1022-1352; 1521-3935
• DOI: 10.1002/1521-3935(20000801)201:13<1532::AID-MACP1532>3.0.CO;2-Z

We present a study of the dispersion polymerization of methyl methacrylate in supercritical carbon dioxide in the presence of poly(dimethylsiloxane)‐monomethyl acrylate. The heterogeneous polymerization is followed in situ by turbidity at a pressure of 330 bar and a temperature of 60°C. The turbidity spectra of the system are measured directly in the autoclave to give the average‐number of particles per unit volume Nav/V and the average‐diameter στ of the particles as function of time. The experimental setup presented here allows to study the early stage of the nucleation and formation of particles. The results indicate that Nav/V increases first and then saturates whereas στ increases steadily during this period. A comparison of the rate of polymerization thus obtained with kinetic data measured in bulk, suggests that the formation of particles proceeds through coagulation of the polymer which is formed in the homogeneous phase.