Preparation Of Lignin/sodium Dodecyl Sulfate Composite Nanoparticles And Their Application In Microcapsules

The water insoluble of lignin limited its process and application seriously.Preparing water dispersed lignin nanoparticles to stabilize Pickering emulsion and further prepare microcapsule is a significant idea to realize the high value utilization of lignin.Here,in this work,lignin/ sodium dodecyl sulfate(SDS)composite nanoparticles(LSNP)with excellent water dispersibility were facilely prepared via acidifying the mixed basic solution of alkaline lignin(AL)and SDS,subsequently,LSNP-stabilized Pickering emulsions were prepared successfully and used as a template for the preparation of lignin/polyurea composite microcapsules(LPMC)by ionic crosslinking and interfacial polymerization.The LPMC was used to encapsulate avermectin(AVM).The performance of LPMC in controlling release and anti-photolysis were tested.The main contents of this study are listed as follows:1.For the first time,LSNP with excellent water dispersibility were facilely prepared via adjusting the pH of the mixed basic solution of AL and SDS to a low value.The formation mechanism of the LSNP was studied and inferred as follows: In the lignin/SDS mixed basic solution,under the drive of hydrophobic force,through self-assembly,the hydrophobic long carbon chain in the SDS molecule and the stretched network structure of lignin macromolecules interweave together and form a mixed micelle.When the pH of the mixed solution is reduced by adding acid,the lignin molecular skeleton contract and clamp the adsorbed SDS to form LSNP.The LSNP were irregular in shape.Heat treatment studies showed that LSNP has a good thermal stability.The phenomenon of agglomeration after sonication showed that the physical composite structure of LSNP is easily destroyed by sonication.LSNP can stabilize oil phase with different polarities and viscosities.LSNP with higher SDS composite rate can stabilize the emulsion with smaller particle size,and the emulsion possess a stability for more than 2 months.2.Based on the LSNP-stabilized Pickering emulsion template,LPMC were prepared by the ionic crosslinking between LSNP and ethylenediamine hydrochloride(EH)ions and interfacial polymerization between ethylenediamine(EDA)and isophorone diisocyanate(IPDI).The microcapsules were spherical in shape and possessed a double-layer structure composed of lignin and polyurea.The effects of process conditions such as stirring rate,SDS amount and pH of aqueous phase on the morphology and size of LPMC were studied and the optimum process conditions were obtained.The encapsulation efficiency of LPMC reached to 85.4% and decreases with the increase of the amount of lignin on shell.The performance of LPMC in controlled-release mainly contributed by the relatively compact polyurea wall were good and could be adjusted by changing the amount of lignin on shell.The compound of lignin significantly enhanced the anti-photolysis property of LPMC.