Abstract
A detailed mechanistic and kinetic study of enzymatically initiated RAFT polymerization is performed by combining enzymatic assays and polymerization kinetics analysis. Horseradish peroxidase (HRP) initiated RAFT polymerization of dimethylacrylamide (DMAm) was studied. This polymerization was controlled by 2-(propionic acid)ylethyl trithiocarbonate (PAETC) in the presence of H2O2 as a substrate and acetylacetone (ACAC) as a mediator. In general, well controlled polymers with narrow molecular weight distributions and good agreement between theoretical and measured molecular weights are consistently obtained by this method. Kinetic and enzymatic assay analyses show that HRP loading accelerates the reaction, with a critical concentration of ACAC needed to effectively generate polymerization initiating radicals. The PAETC RAFT agent is required to control the reaction, although the RAFT agent also has an inhibitory effect on enzymatic performance and polymerization. Interestingly, although H2O2 is the substrate for HRP there is an optimal concentration near 1 mM, under the conditions studies, with higher or lower concentrations leading to lower polymerization rates and poorer enzymatic activity. This is explained through a competition between the H2O2 acting as a substrate, but also an inhibitor of HRP at high concentrations.
Highlights
Enzymes are fundamental to biological processes due to their ability to efficiently catalyze reactions [1]
This study examines how the reaction rate of Horseradish peroxidase (HRP)-catalyzed reversible addition-fragmentation polymerization (RAFT) polymerization is affected when the reaction components HRP, chainare transfer agent (CTA), hydrogen peroxide, and ACAC are varied
At a sufficiently high ACAC loading, essentially all radicals generated by HRP will react with ACAC to create carbon centered radicals capable of initiating polymerization, leading to a plateau in rate with ACAC loading
Summary
Enzymes are fundamental to biological processes due to their ability to efficiently catalyze reactions [1]. RDRP variant which offers distinct advantages such as as compatibility [17,31,32,33,34,35] This is in addition to the deoxygenation processes facilitated by enzymes such glucose with oxidase a widetorange of functional groups and the ability to be run under simple and near ambient promote polymerization under simple conditions [36,37,38,39]. Trithiocarbonate is used to facilitate the uniform propagation of polymers as the monomers are HRP initiated RAFT has been demonstrated as a rapid and versatile polymerization technique capable added to the living chains in a controlled fashion. The target of this work is to correlate the observed polymerization reaction kinetics to the underlying enzymatic activity, guiding how to optimize the HRP-catalyzed RAFT polymerization
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