Online Monitoring of Molecular Weight and Other Characteristics during Semibatch Emulsion Polymerization under Monomer Starved and Flooded Conditions

Abstract

Reaction kinetics in semibatch emulsion polymerization of methyl methacrylate, were monitored by automatic continuous online monitoring of polymerization reactions (ACOMP). Semibatch reagent feed to the reactor at different flow rates allowed the transition between the monomer starved and flooded regimes and the approach to and maintenance of near steady state conditions to be monitored and quantified, and yielded relationships between flow regimes and monomer conversion kinetics, polymer weight-average molecular weight Mw, and intrinsic viscosity (η)w. Polymer molecular weight distributions togetherwithlatexparticlesizeandnumberplayanimportantroleindefiningthemacroscopiccharacteristics and performance of polymeric materials. The change in the monomer feed rates during reaction allowed simultaneous influence on and verification of the evolution of these parameters during synthesis. When flow rate changes to the reactor were made it was verified that the characteristic rate of achieving the new pseudosteady state was close to the first order reaction rate. Multidetector size exclusion chromatography was used to cross-check results and measure full distributions of endproducts. Latex polymer size was measuredwithdynamiclightscattering.AnimportantadvanceforthisfieldisthatpolymerMwisdetermined continuously during the reaction and in an absolute fashion, based on multiangle light scattering detection available.