Microgel synthesis: Kinetics, particle formation and reactor modelling
Microgels are soft polymer particles with a wide range of possible applications, such as drug delivery system or as catalysis matrix. However, the polymerization kinetics as well as mechanisms of the microgel formation and growth in different reaction systems are not completely understood yet and a combination of computational, experimental and modeling approaches will allow to provide an efficient tool to characterize such phenomena. Therefore, we investigate the kinetic mechanism during microgel formation by precipitation polymerization in aqueous phase along with our partners (DWI, AVT.SVT) by an integrated computational, experimental, and model-based approach. A dynamic mathematical model for the chemical synthesis of poly(N-isopropylacrylamide) (PNIPAM) and poly(N-vinylcaprolactam) (PVCL) microgels is developed.
Here at the LTT, we focus on the computational examination of liquid phase reaction kinetics via Quantum Mechanical (QM) methods and reactive Molecular Dynamics (MD) Simulations. A large number of reactions involved in the microgel synthesis and a changing reaction environment make an exclusive experimental analysis of the reaction rates challenging. Therefore, the computational analysis adds perfectly to experiments and allows for a deeper understanding of the underlying reaction kinetics. In order to obtain liquid phase reaction rate constants, we employ QM methods to calculate gas phase reaction rate constants first. After that we use solvation models such as COSMO-RS to account for solvation effects and update the rate constants, thus receiving the desired liquid phase reaction rate constants.
This approach and the variety of methods enables us to identify elementary reactions and their rate constants over a wide range reaction environments to evaluate the significance of reactions, and to understand the microgel growth process on an atomistic level.
This research is done as part of the Sonderforschungsbereich "SFB 985 - Functional Microgels and Microgel Systems" and results are shared actively with fellow researchers.
Kröger, Leif C., Wassja A. Kopp, and Kai Leonhard. Prediction of chain propagation rate constants of polymerization reactions in aqueous NIPAM/BIS and VCL/BIS systems. The Journal of Physical Chemistry B 121.13 (2017): 2887-2895.
Janssen, Franca AL, et al. Synthesis of Poly (N-vinylcaprolactam)-Based Microgels by Precipitation Polymerization: Process Modeling and Experimental Validation. Industrial & Engineering Chemistry Research 56.49 (2017): 14545-14556.
Janssen, Franca AL, et al. Kinetic Modeling of Precipitation Terpolymerization for Functional Microgels. Computer Aided Chemical Engineering. Vol. 43. Elsevier, 2018. 109-114.