Polymerization mechanism of natural lacquer sap with special phase structure

Abstract

Lacquer sap is a water-in-oil natural emulsion with high viscosity. in nature, it exudes from the phloem of lacquer tree to repair its wounds in the presence of o 2. So far, it is unclear how rapid and smooth polymerization of urushiol is achieved in such a viscous sap. Here, we find that there is a diffuse interface layer with 2.43 nm of thickness between two phases. The interface layer consists of urushiol, urushiol-laccase complex, urushiol-stellacyanin complex and water-insoluble glycoprotein. Polymerization of urushiol is realized by multicomponent synergistic effect. Radicals are first formed by laccase-catalyzed oxidation of urushiol at the interface layer, then are transferred to the urushiol oil phase via wate-insoluble glycoprotein and initiate the polymerization of urushiol there. Stellacyanin inhibits the formation of certain radicals and controls the concentration of phenoxy radicals at the interface layer. Through the inhibition of radicals by stellacyanin and the electron transfer mediated by water-insoluble glycoprotein, the polymerization of urushiol at the interface layer is inhibited. This ensures that o 2 can continuously penetrate into the aqueous phase to oxidize the reduced laccase so that the urushiol polymerization can continue smoothly. this polymerization mechanism provides an idea for developing new chemical reaction systems.

Quantitative Analysis of Blended Asian Lacquers Using ToF–SIMS, Py–GC/MS and HPLC

“…In the high-mass range ( m/z 600–700), the ToF–SIMS spectra of Japanese T. vernicifluum and Vietnamese T. succedaneum lacquer films showed urushiol–urushiol and laccol–laccol dimers, respectively. Spectra of blended lacquers indicated several molecular ions, which correspond with urushiol–laccol dimers generated by cross-coupling [ 32 , 33 , 34 ]. The polymerization mechanism in mixed lacquers of Japanese T. vernicifluum and Vietnamese T. succedaneum can be explained as follows.…”

Improved Measurements of the Physical Properties of Oriental Lacquers Using Atomic Force Microscopy and a Nanoindenter

“…Figure 2a-d Lacquer sap is a water-in-oil emulsion. When lacquer sap is dried to produce a film, the polysaccharides and glycoproteins merge into the lipid component of the emulsion [18,21]. Water evaporates, resulting in micro-cavities in the lacquer film.…”

“…The main constituents of natural lacquer-lipids-are catechol derivatives with a linear alkenyl group: a C15 or C17 chain. The drying mechanism of Oriental lacquer mainly Polymers 2021, 13, 1395 2 of 13 proceeds by two processes [18][19][20][21][22]. The first step is laccase-catalyzed oxidation.…”

Nano-emulsification of oriental lacquer sap by ultrasonic wave propagation: Improvement of thin-film characteristics as a natural resin

“…1 ). The lacquer sap consists of water-in-oil (W/O) emulsion droplets [15] , [16] , [17] . Urushiol, urushiol-laccase, -stellacyanin complexes, and water-insoluble glycoprotein exist in the interlayer between the two phases.…”

“…Meanwhile, the polysaccharide inhibits rapid evaporation of water, which in turn contributes to the maintenance of laccase enzyme activity. However, based on the emulsion form of lacquer sap, Yang et al explained that the radicals generated by the laccase-catalysed oxidation of urushiol at the interface layer can be transferred to the urushiol in the oil phase via water-insoluble glycoprotein, which initiates the polymerisation of urushiol in the oil phase [16] . At the interlayer, stellacyanin inhibits certain radicals, suppressing urushiol polymerisation at the W/O emulsion interlayer of the lacquer sap.…”