Online tracing of molecular weight evolution during radical polymerization via high-resolution FlowNMR spectroscopy

High-resolution FlowNMR was coupled to a continuous flow reactor to monitor polymer molecular weight evolution online by diffusion ordered NMR spectroscopy. Polymers were synthesized by reversible addition fragmentation chain transfer polymerization in continuous flow. The setup allows to target various polymer chain lengths in a dynamic manner without requiring additional purification or sample preparation. Obtaining molecular weight information in this manner is shown to be more accurate than classical SEC analysis at comparable measurement times, with relative errors around 5%

Update and critical reanalysis of IUPAC benchmark propagation rate coefficient data

The dataset used to generate IUPAC benchmark Arrhenius parameters for propagation rate coefficients in radical polymerization is extended and reanalyzed, taking into account systematic interlaboratory variation

Controlling Molecular Weight Distributions Through the Mixing of Low Dispersity Polymer Samples: A Predictive Framework

The physical properties of polymer samples are dependent on the overall shape and breadth of the molecular weight distribution (MWD). A small number of methods are available to tune the shape and characteristics of MWDs based on influencing controlled radical polymerizations and on mixing of individual distributions. However, no systematic framework exists to date to predict the characteristics and shapes of artificial MWDs prior the experiments. In this work we present such framework based on interpolation of individual distributions.</div

Mapping Dithiobenzoate-Mediated RAFT Polymerization Products via Online Microreactor/Mass Spectrometry Monitoring

2-cyano-2-propyl dithiobenzoates (CPDB)-mediated reversible addition-fragmentation chain transfer (RAFT) polymerization was monitored by online flow microreactor/mass spectrometry. This enabled the reactions to be followed in a time-resolved manner, closely resolving product patterns in the reaction mixtures at any point in time. RAFT polymerization was investigated for low RAFT to monomer ratios, enabling the monitoring of the early stages of a typical RAFT polymerization. The expected transition from pre- to the RAFT main equilibrium is observed. However, very high abundancies for cross-termination products were also identified, both in the pre- and main equilibrium stage. This is a somewhat surprising result as such products have always been expected, but to date have not been observed in the majority of studies. Product isolation and NMR analysis revealed that cross-termination occurs in the para position of the benzoate ring and becomes fully irreversible via re-aromatization of the ring in a H-shift reaction. The present data suggest a pronounced chain-length dependence of the cross-termination reaction, which would explain why the products are seen here, but not in other studies

Autonomous Size-Targeting for Block Copolymer Nanoparticles

Using the combination of flow synthesis with online dynamic light scattering (DLS) analysis for particle size characterization and fully autonomous computer control allows for reproducible and targetable synthesis of nanoparticles from block copolymer (BCP) solutions by rapid mixing with water in a defined micromixer environment. Using Bayesian optimization (BO), nanoparticle sizes become programmable and preselectable, and awide range of sizes can be obtained per used BCP. Specifically, we show for a series of polystyrene-b-poly(N,N- dimethyl acrylamide) and polystyrene-b-poly(poly(ethylene glycol) methyl ether acrylate) BCPs, how particles spanning from 130 to 280 nm can be systematically targeted, with sizes between 100 and 1000 nm being at least in principle also achievable. Further, Pareto fronts for the individual synthesis parameters overall flow rate, water volume fraction and polymer concentration are obtained from the established routines and presented. This BO approach highlights the efficacy of autonomous flow platforms in achieving precise control over polymer self-assembly processes, offering an optimal production window for the development and optimization of polymeric nanostructures in diverse fields such as drug delivery and materials science

Muconic acid isomers as platform chemicals and monomers in the biobased economy

status: publishe