Biocatalytic nanoparticles for the stabilization of degassed single electron transfer-living radical pickering emulsion polymerizations

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.

Access to tough and transparent nanocomposites via Pickering emulsion polymerization using biocatalytic hybrid lignin nanoparticles as functional surfactants

“…2d). These results not only validate our previous findings on the use of GOx-chi-LNPs as efficient degassing stabilizers for Pickering emulsions and controlled radical polymerization processes, 57 but also demonstrate that these functional surfactants can be applied in industrially relevant FRP processes without the need of organic solvents or tedious and high cost degassing protocols (i.e. degassing with inert gas).…”

“…1a). 57 Briefly, first negatively charged LNPs (approximate diameter 100 nm by DLS) were prepared from kraft lignin by solvent dilution following previously reported methodologies with minor modifications. 52 Afterwards, GOx-chi-LNPs were prepared by sequential adsorption of chitosan (100 mg g -1 LNPs) and GOx (10 mg g -1 chi-LNPs) onto LNPs, respectively.…”

“…After enzyme immobilization, GOx-chi-LNPs showed a high enzyme immobilization efficiency (88%), and a high retention of the enzyme activity (Table S2). 57 To evaluate differences in particle size and morphology, negatively charged (LNPs) and positively charged (chi-LNPs and GOxchi-LNPs) lignin particles were imaged by SEM. For all the colloidal lignin particles, well-defined and spherical particles could be observed ( Fig.…”

“…19 As we envisioned previously, the improved thermal stability of GOx immobilized onto chi-LNPs opens a possibility to apply these surfactants in polymerization processes such as FRP that operate at elevated temperatures. 57 Therefore, we decided study the influence of the concentration of GOx-chi-LNPs on the colloidal quality of the latex dispersions obtained from the FRP of styrene-based Pickering emulsions using AIBN as a thermal initiator at 65 °C (Fig. 2b).…”

“…Recently, our research group reported a material-efficient method for the fabrication of biocatalyst loaded LNPs and their application as functional surfactants for enzyme-degassed controlled radical polymerization in Pickering emulsions. 57 This approach consists of a two-step adsorption immobilization process where chitosan (chi) and glucose oxidase (GOx) were adsorbed onto LNPs to produce biocatalytic hybrid particles (GOx-chi-LNPs) capable to circumvent the oxygen inhibition of the polymerization process. We also found that the enzyme immobilization GOx increased the thermal stability of GOx from 55 °C to 75 °C, which was ascribed to the inherent ability of the particles to scavenge the hydrogen peroxide generated during the degassing step.…”