In this work, the combination of different modeling approaches with in‐line proton nuclear magnetic resonance (1H‐NMR) spectroscopy is used to assist the transfer of a reversible addition‐fragmentation chain transfer (RAFT) polymerization of methyl methacrylate to a micro‐scale reactor. This approach is then applied to find the optimal process parameters like temperature or residence time as well as the best composition of the reaction mixture in order to optimize the conversion and molecular characteristics of the synthesized polymer. A kinetic model based on ordinary differential equations implemented in the program Predici is first validated based on experimental data of reactions performed at various temperatures. Further on, two glass chip reactors and a coil reactor are used and combined in different ways to investigate the influence of the reactor geometry on the polymerization process. This optimization step is assisted by multiphysics modeling that focuses on the heat transfer properties of specific areas inside the reactors. This experimental setup is used successfully to carry out a stationary polymerization. This study shows that instationary experiments in a micro‐fluidic reactor system equipped with in‐line analytics allow for the fast development of a kinetic model for RAFT polymerizations.
Reversible addition-fragmentation chain transfer (RAFT) polymerization is one of the most common controlled polymerization techniques to prepare well-defined, rather narrow dispersed polymers due to reduced demands in reactant preparation. Despite these advantages, RAFT polymerization was so far primarily utilized on small laboratory scales. This study presents a first step to a scaled-up RAFT polymerization by developing and experimentally validating a kinetic model on the example of the polymerization of 4-vinylpyridine (4VP), which to date is not described in the literature. With the implementation of the results from modeling, the synthesis process was extended to a medium scale (from 6 to 36 g), while the same high conversions, molar mass, and low dispersity as in the smaller scale were achieved. The process is also optimized regarding the high degree of livingness necessary for using the 4VP polymers as a macro-RAFT agent in the subsequent reaction step for the synthesis of poly(4-vinylpyridine)-b-polystyrene diblock copolymers by RAFT dispersion polymerization.
In this work, the reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization of poly(N,N-dimethylacrylamide-co-N-isopropylacrylamide)-b-polystyrene is developed with the aim of scale-up of the polymer synthesis. Influences on the stability of the emulsion, reaction kinetics, and product quality are examined, compared between small-scale and bench-scale syntheses, and discussed in detail. The block copolymer lattices are studied via temperature-dependent dynamic light scattering measurements in order to investigate the effects of the scale-up on the thermosensitive behavior of the block copolymer and on emulsion stability. Conversion determination and polymer characterization are attained through 1 H nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography, respectively. The emulsion polymerization is successfully scaled up after several changes in the reaction composition and shows promising results regarding desired properties of the polymer.
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