Abstract
Synthetic polymers are indispensable in many different applications, but there is a growing need for green processes and natural surfactants for emulsion polymerization. The use of solid particles to stabilize Pickering emulsions is a particularly attractive avenue, but oxygen sensitivity has remained a formidable challenge in controlled polymerization reactions. Here we show that lignin nanoparticles (LNPs) coated with chitosan and glucose oxidase (GOx) enable efficient stabilization of Pickering emulsion and in situ enzymatic degassing of single electron transfer-living radical polymerization (SET-LRP) without extraneous hydrogen peroxide scavengers. The resulting latex dispersions can be purified by aqueous extraction or used to obtain polymer nanocomposites containing uniformly dispersed LNPs. The polymers exhibit high chain-end fidelity that allows for production of a series of well-defined block copolymers as a viable route to more complex architectures.
Highlights
Synthetic polymers are indispensable in many different applications, but there is a growing need for green processes and natural surfactants for emulsion polymerization
Our approach to fabricate multifunctional Pickering emulsion polymerization stabilizers started with production of biocatalyst-loaded lignin nanoparticles (LNPs) (GOx-chi-LNPs) via a two-step adsorption immobilization strategy (Fig. 1)
We aimed to develop a material-efficient process and in order to simplify the LNPs production process we did not use dialysis as a purification step but instead evaporation for the solvent removal
Summary
Synthetic polymers are indispensable in many different applications, but there is a growing need for green processes and natural surfactants for emulsion polymerization. The polymerization of hydrophobic monomers remains scarcely explored, and is hitherto limited to ATRP-mediated miniemulsion processes using soluble ionic surfactants such as sodium dodecyl sulfate (SDS)[21], which could disrupt the activity of the enzyme at longer reactions times[26] Some of these previously reported systems require the addition of sacrificial substrates (e.g., sodium pyruvate) to act as scavengers to consume the hydrogen peroxide generated during the GOx-catalyzed degassing step and thereby avoid giving rise to detrimental Fenton-like redox processes[19,21]. Pickering emulsion polymerizations stabilized by organic or inorganic particles have gained a great attention over conventional emulsion polymerization processes due to a more-stable emulsification behavior, and the ability to produce composites with improved properties[27,28] These systems have been scarcely applied in RDRP techniques such as ATRP or RAFT to generate hybrid latexes with a reasonable extent of control[29,30]. We rationalized their potential ability to self-scavenge H2O2 during the polymerization, which was expected to be beneficial for the activity of GOx and control the polymerization without the use of any extraneous reducing agents
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