| Lignocellulose is a rich renewable resource,which can be separated to produce chemical products and bio-based nanomaterials after pretreatment.This way can achieve high-value utilization of lignocellulose components.In this study,wheat straw was pretreated by aqueous p-toluenesulfonic acid(p-TsOH)of 70 wt%,80?,10 min.The spent liquor and purified cellulose were recovered by fractionation.The Lignin nanoparticles(LNPs)and Lignin containing nanofibers(LCNFs)were prepared by combining anti-solvent and ultrasonic treatment.They were combined with PVA to prepare excellent bio-based nanocomposites.The main contents are as follows:(1)LNPs were prepared by using anti-solvent way from p-TsOH.The dissolved lignin could be simply precipitated as LNPs by diluting the spent liquor to 4%.SEM and AFM analyses showed that LNPs was an oblate spheroid morphology and a uniform particles size distribution,the particle size of LNPs were 33.9 nm,the average height were 7.8 nm.When loading of LNPs were 6%,LNPs/PVA nanocomposite films could block 100%and 95%of UV light at 315 and 400 nm,respectively,and showed 80%antioxidant activity.In addition,the respective maximum TS and TM were 59.7 MPa and 2.07 GPa,respectively,which were increases of approximately 36%and 104%compared with those of pure PVA film.Thus,the LNPs/PVA nanocomposite films showed improved UV resistance,mechanical properties,thermal stability and antioxidant activity and could be used as additional multifunctional agents in the fields of biodegradable plastics,tissue engineering and UV-protective biobased materials.(2)LCNFs were successfully prepared from wheat straw by using an acid hydrotrope of p-TsOH combined with ultrasonication.p-TsOH pretreatment was applied below 80?to selectively remove hemicellulose and lignin,generated purified cellulose fibers of cellulose content was 90%.LCNFs were prepared by using high-frequency ultrasonic treatment purified cellulose for 6 min at 800 W,1200 W,1600 W.AFM and TEM analyses showed that with the increasing of ultrasonic frequency from 800 W to 1600 W,the average diameters of LCNFs were decreased from 20.01 nm to 10.12 nm,the proportion of diameters below 20 nm were increased from 58%to 93.33%.The FTIR and XRD results indicated that the molecular structures and cellulose crystallinity were not influenced during the ultrasonic.5 wt%loadings of LCNFs prepared LCNFs/PVA composite films with PVA,which of performance were studied.The result displayed that LCNFs improved thermal performance and hydrophobic properties of nanocomposite films,compared with the pure PVA films.Although the tensile stress and Young's modulus,were strengthened remarkably,the elongation at the break was slightly decreased.Thus,LCNFs were expected to become candidate material for various applications.(3)LCNFs were darkly oxidized to prepare DAC by using sodium periodate(NaIO4).DAC/PVA hydrogel was prepared by hydroxyl aldehyde condensation reaction was catalyzed2 mol/L HCl at 70?for 2 h.SEM analysis showed that the three-dimensional network structure belonged to DAC/PVA hydrogel,the increase of DAC loading from 1 wt%to 2 wt%,the degree of crosslinking got increaser gradually,the pore size changed smaller gradually,the net structure changed denser and denser.This result was confirmed by the swelling performance test.Cyclic compression tested 1 wt%DAC/PVA hydrogel,below 70%strain,the maximum stress reached5.765 MPa.Due to the increasing of strain,the compressive stress of the hydrogel would be enhanced.The results showed that the hydrogel had excellent compression resistance.By the high temperature test,the hydrogel showed excellent high temperature resistance at sterilization condition of 121?,30 min.To study the drug release process and mechanism of hydrogel by testing antibacterial performance of ampicillin embedded hydrogel.The results showed that hydrogel was used to embed and sustained-release drugs.Thus,hydrogel was excepted to have potential application,such as wound dressing,tissue engineering. |
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