On the Importance of Accurate Internal Temperature Measurements in the Microwave Dielectric Heating of Viscous Systems and Polymer Synthesis

The relationship among viscosity and microwave absorptivity of organic solvents/polymers, the stirring rate, and the resulting errors in temperature measurement upon microwave dielectric heating is investigated. For a set of common solvents and polymers covering a broad range of viscosities and microwave absorptivities signifi cant variations in the temperatures simultaneously recorded by external infrared sensors and internal fi ber-optic probes are experienced. The implications of these apparent diffi culties in establishing the genuine reaction temperature for microwave-heated viscous reaction systems are evaluated for a ring-opening polymerization and for the synthesis of a surfactant.