Continuous direct on-line reaction monitoring of a controlled polymerisation via dielectric measurement

This paper reports the application of an extremely facile methodology for monitoring the progress of chemical reactions. This has been exemplified by successfully following the progress of a controlled ring opening polymerisation of ε-caprolactone which has been successfully monitored at high temperature (>100 °C), using a direct, on-line measurement of the system dielectric properties. The data was obtained via the use of a coaxial probe in a standard quick fit reaction flask. The on-line measurement has been related to a calibration curve and from this comparison it has been shown that dielectric data can be used to predict the molecular weight of the polymer at a particular point in the reaction. This in turn allowed isolation of a product with desired molecular weight and polydispersity index values, by enabling the reaction to be terminated prior to the point where reaction control is lost due to the appearance of side reactions. These on-line measurements were corroborated by comparison to conventional and accepted off-line measurement techniques.