title: Prediction of Chain Propagation Rate Constants of Polymerization Reactions in Aqueous NIPAM/BIS and VCL/BIS Systems.
abstract: Microgels have a wide range of possible applications and are therefore studied with increasing interest. Nonetheless, the microgel synthesis process and some of the resulting properties of the microgels, such as the cross-linker distribution within the microgels, are not yet fully understood. An in-depth understanding of the synthesis process is crucial for designing tailored microgels with desired properties. In this work, rate constants and reaction enthalpies of chain propagation reactions in aqueous N-isopropylacrylamide/N,N'-methylenebisacrylamide and aqueous N-vinylcaprolactam/N,N'-methylenebisacrylamide systems are calculated to identify the possible sources of an inhomogeneous cross-linker distribution in the resulting microgels. Gas-phase reaction rate constants are calculated from B2PLYPD3/aug-cc-pVTZ energies and B3LYPD3/tzvp geometries and frequencies. Then, solvation effects based on COSMO-RS are incorporated into the rate constants to obtain the desired liquid-phase reaction rate constants. The rate constants agree with experiments within a factor of 2-10, and the reaction enthalpies deviate less than 5 kJ/mol. Further, the effect of rate constants on the microgel growth process is analyzed, and it is shown that differences in the magnitude of the reaction rate constants are a source of an inhomogeneous cross-linker distribution within the resulting microgel.
authors.affiliation: Chair of Technical Thermodynamics, RWTH Aachen University , D-52062 Aachen, Germany.
authors.forename: Leif C
authors.identifier: 0000-0003-0463-1726
authors.initials: LC
authors.lastname: Kröger
authors.affiliation: Chair of Technical Thermodynamics, RWTH Aachen University , D-52062 Aachen, Germany.
authors.forename: Wassja A
authors.initials: WA
authors.lastname: Kopp
authors.affiliation: Chair of Technical Thermodynamics, RWTH Aachen University , D-52062 Aachen, Germany.
authors.forename: Kai
authors.initials: K
authors.lastname: Leonhard