Preparation Of UCST Type Lignin-based Thermo-responsive Materials By EATRP And Its Properties

Lignin has the advantages of abundant and renewable source,high carbon content and biodegradablilty,but the complex structure of lignin limits its high value application.At present,it can be utilized by degradation,modification and nanosizing.In this paper,deep eutectic solvent lignin(DES-lignin)was used as the modified objects.The DES-lignin was degraded by electrochemical oxidation and its content of phenol hydroxyl was increased.The lignin-based thermosensitive material was prepared by eATRP method.Ethanol/saline solvent anti-solvent self-assembly method was used to coat ibuprofen by the lignin-based thermosensitive material,which formed the nanoparticles.The release in vitro was performed.The specific research contents and results are as follows:(1)DES-lignin which was extracted from poplar by deep eutectic solvent was raw materials.An electrocatalytic oxidative approach using tert-butyl hydroperoxide(t-BuOOH)as oxidant was used to degrade deep eutectic solvent lignin(DES-lignin).The effect of electrolysis time,DES-lignin concentration,current density and amount of t-BuOOH on phenolic hydroxyl content of DES-lignin by electrochemical catalyzed oxidative degradation was investigated.The results showed that the optimum conditions were electrolysis time of 3 h,DES-lignin concentration of 33.3 g/L,current density of 10 mA/cm2 and the t-BuOOH of 5 mmol.In order to explore the evolution of molecular structure and its reaction mechanism when DES-lignin was electrochemical degraded,DES-lignin and electrochemical degraded DES-lignin were characterized by gel permeation chromatography(GPC),H nuclear magnetic resonance(1H-NMR),Fourier transform infrared spectroscopy(FT-IR),two dimensional heteronuclear single quantum coherence nuclear magnetic resonance spectroscopy(2D-HSQC NMR),and thermogravimetric analysis(TG).The results showed that the phenolic hydroxyl group increased from 1.03 mmol/g to 5.83 mmol/g,which increased its active site.Mw and Mn decreased by 30.15%,10.44%,respectively,the dispersion coefficient decreased by 22%,the molecular weight distribution of degraded DES-lignin fragments was narrower and more uniform.The β-O-4 bond decreased by 14.49%,the aryl ether bond decreased.The residual carbon increased from 1.38%to 21.10%at 800℃,which indicated the thermal stability improved.(2)The electrochemical degraded DES-lignin was used as raw material lignin(Lignin).Lignin-based thermosensitive polymer with the upper critical solution temperature(Lignin-g-PDMAPS)was prepared by grafted zwitterionic polymers onto lignin though electrochemically mediated atom transfer radical polymerization(eATRP)method.The structure and property of the Lignin-g-PDMAPS polymer were characterized by the fourier transform infrared spectrum(FT-IR),nuclear magnetic resonance(NMR),X-ray electron spectroscopy(XPS),dynamic light scattering(DLS),differential scanning calorimeter(DSC).The results showed that the Lignin-g-PDMAPS polymer was successfully prepared by eATRP.Furthermore,the effect of catalyst structure,applied potential,amount of Lignin-Br,Lignin-g-PDMAPS concentration,NaCl concentration on UCST of Lignin-g-PDMAPS were investigated.It was worth noting that polymerization was well controlled when the ligand was tris(2-aminoethyl)amine(Me6TREN),applied potential was-0.38 V and the amount of Lignin-Br was 100mg.And the UCST of the 1 mg/ml Lignin-g-PDMAPS aqueous solution was 51.47℃,the molecular weight was 8,987 g/mol,and the particle size was 318 nm.It was also found that the UCST increased and the particle size decreased with the Lignin-g-PDMAPS polymer concentration increased,and the UCST decreased and the particle size increased with the NaCl concentration increases.(3)The Lignin-g-PDMAPS thermosensitive polymer was used to coat ibuprofen through self assembly by an ethanol/saline solvent anti-solvent method to obtain lignin thermosensitive polymer coated ibuprofen nanoparticle(IBU@LTPN).The releasing behavior of IBU@LTPN at different temperatures and pH values was investigated.Differential scanning calorimetry(DSC),scanning electron microscopy(SEM),and fourier transform infrared spectroscopy(FT-IR)were used to characterize the structure and properties of IBU@LTPN.The results indicated that the coating rate of IBU@LTPN was 68.55%,the upper critical solution temperature(UCST)of IBU@LTPN was 38.55℃,the morphology of the IBU@LTPN was ellipsoidal.IBU@LTPN exhibited obvious temperature response property.The 48 h cumulative release was 75%at 42℃ when the temperature was above UCST.The 48 h cumulative release was 36%at 38℃ when the temperature was below UCST.In addition,the difference of cumulative release under varied pH indicated its good pH response behavior.Furthermore,IBU@LTPN had obvious anti-specific protein adsorption properties and the dosage was safe.This study provides a strategy for drug coating and controlled release,which improves the commercial initiatives and market application potential of lignin.