Determination of Individual Diffusion Coefficients in Evolving Binary Mixtures by Taylor Dispersion Analysis: Application to the Monitoring of Polymer Reaction

This study demonstrates that it is possible to get valuable information on the individual populations of a binary mixture from the signal obtained by Taylor dispersion analysis (TDA). In the case of mixtures composed of two populations of different sizes (such as a monomer/polymer mixture), the information available from TDA is not restricted to an average diffusion coefficient or an average hydrodynamic radius calculated on the entire binary mixture. In this work, TDA was used to monitor a polymerization reaction. In this scope, it has been possible to determine the degree of conversion and the weight average hydrodynamic radius of the polymer at different reaction times. Three different methods are proposed for the data processing of taylorgrams derived from polymerization mixtures or, more generally, for taylorgrams of binary mixtures. These three methods, either based on deconvolution or on integration of the signal, were found to give similar results. TDA results obtained for a model binary mixture of acrylamide and standard polyacrylamide were consistent with DLS experiments provided that the differences in the type of average hydrodynamic radius values between the two methods are taken into account. An example of application to the monitoring of acrylamide radical polymerization is shown.