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Chemical science 13(38), 11304-11311 (2022). doi:10.1039/D2SC03153A, Published by RSC, Cambridge

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2021; Aachen : RWTH Aachen University 1 Online-Ressource : Illustrationen, Diagramme (2021). = Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2021, Microgels are functional polymers with diverse applications in liquid-liquid phase separation, switchable membranes, or drug delivery. The diverse applications require microgels with specific product properties. The properties of microgels are determined during the microgel synthesis, as microgels are products by process. The efficient synthesis of functional microgels is necessary for the increased application of microgels in research and industry. Model-based methods are a potential way to enable the efficient synthesis of functional microgels. Model-based methods require a quantitative model of how the microgel synthesis conditions affect the properties of the microgel product. First, we therefore derive a mechanistic model of the microgel synthesis kinetics including mole balances of all reactants and additional equations to model key microgel properties like the cross-linker density. We use kinetic parameters from first principle calculations and estimate kinetic parameters based on experimental data and perform identifiability analysis of respective parameters. Second, we extend the model of the microgel synthesis kinetics to also include microgel growth and the hydrodynamic microgel radius. We introduce assumptions to reduce the number of model parameters to be estimated based on the limited available experimental data. We validate the model results with experimental data across three orders of magnitude gathered from different research groups. The agreement between model results and experimental data is suitable for varying synthesis conditions. Third, we apply the model in in-silico simulations and optimizations. We use dynamic optimization to determine fed-batch recipes that allow for a desired radial distribution of cross-linker in the microgel, while maintaining the monomer conversion. We also use dynamic optimization to minimize the environmental impact factor of a microgel synthesis, while maintaining microgel quality indicators like the hydrodynamic microgel radius. Fourth, we use the model in model-based experimental analysis to understand the effect of initiator and cross-linker feeding and ramps in the reactor temperature on the microgel size Model-based experimental analysis shows that the low initiator concentration and low initial reactor temperatures increase the hydrodynamic radius of microgels. Based on these results, we suggest a batch recipe that enables the simplified synthesis of microgels with a large hydrodynamic radius. The suggested recipe is validated experimentally and experimental data and simulation results show good agreement. Fifth, we apply the model in model-based design of microgel syntheses to obtain microgels with a desired radial distribution of functional monomers. We determine three fed-batch synthesis recipes with the aim of accumulating the functional monomer in the core of the microgel, accumulating the functional monomer in the shell of the microgel, or obtaining a homogeneous distribution. We validate the suggested synthesis by executing the respective recipes. The obtained experimental data shows good agreement between simulation results without any iteration loops.In summary, we show that model-based microgel synthesis is a working and efficient method for the synthesis of functional microgels with desired product properties., Published by RWTH Aachen University, Aachen

A highly selective and sensitive optical sensor was developed to colorimetric detect trace Fe3+ ions in aqueous solution. The sensor was the sulfasalazine (SSZ) functionalized microgels (SSZ-MGs), which were fabricated via in-situ quaternization reaction. The obtained SSZ-MGs had hydrodynamic radius of about 259 &plusmn, 24 nm with uniform size distribution at 25 &deg, C. The SSZ-MG aqueous suspensions can selectively and sensitively response to Fe3+ ions in aqueous solution at 25 &deg, C and pH of 5.6, which can be quantified by UV-visible spectroscopy and also easily distinguished by the naked eye. Job&rsquo, s plot indicated that the molar binding ratio of SSZ moiety in SSZ-MGs to Fe3+ was close to 1:1 with an apparent association constant of 1.72 &times, 104 M&minus, 1. A linear range of 0&ndash, 12 &mu, M with the detection limit of 0.110 &mu, M (0.006 mg/L) was found. The obtained detection limit was much lower than the maximum allowance level of Fe3+ ions in drinking water (0.3 mg/L) regulated by the Environmental Protection Agency (EPA) of the United States. The existence of 19 other species of metal ions, namely, Ag+, Li+, Na+, K+, Ca2+, Ba2+, Cu2+, Ni2+, Mn2+, Pb2+, Zn2+, Cd2+, Co2+, Cr3+, Yb3+, La3+, Gd3+, Ce3+, and Bi3+, did not interfere with the detection of Fe3+ ions.