Preparation And Properties Of Nanocellulose Reinforced Electrospun Mats

Nanocellulose has the advantages of high availability,high crystallinity,high strength,large specific surface area and biocompatibility,which makes it an ideal candidate for enhancing high-performance composite materials.Nanocellulose can be modified by surface chemical functionalization and compounded with metal nanomaterials to give it more excellent performance properties.Electrospinning is one of the most important methods for preparing nanocomposites.The prepared non-woven mesh fibrous mats have broad application prospects in many fields.In this paper,nano-cellulose and its composites are used as functional fillers to prepare fibrous mats by electrospinning,which gives the material unique properties and aims to broaden the potential applications of nanocellulose reinforced composites.In this study,nanocellulose crystals(CNC)and carboxylated nanocellulose crystals(CCN)were prepared.An electrospinning process was utilized to fabricate composite fibrous mats of poly(methyl methacrylate)(PMMA)reinforced with CNC.The enhancement mechanism of CNC on composite fibrous mats was explored.The effects of CNC and environmental humidity on the porous structure and rough surface formation of fibers were analyzed.On this basis,functional modification of nanocellulose was carried out.and the nanocellulose used as a template to synthesize silver nanoparticles(AgNPs)and magnetic particles(CoFe2O4).respectively.The composites were used as multifunctional fillers and mixed into the different polymer matrix to synthesize composite fibrous mats by electrospinning.The effect of nanocellulose/metal composites on the morphology and properties of electrospun fibers was explored,and the application fields of nanocellulose-based functional fillers to composite fibrous mats were expanded.The specific research contents and conclusions are as follows:(1)The research was carried out by using microcrystalline cellulose as raw material,preparing CNC by hydrolysis of sulfuric acid.The prepared CNC exhibited rod-like structure,and had high crystallinity of 81.2%.The well-dispersed CNC/DMF suspension was prepared by solvent exchange.The CNC/PMMA composite fibrous mats with different CNC additions were prepared by electrospinning.The effects of CNC addition on the microstructure,thermal properties and mechanical properties of composite fibrous mats were investigated.The CNC were uniformly distributed in both the spinning solution and the PMMA matrix.The prepared composite fibers exhibited uniform and smooth nanofibers.As the amount of CNC increased,the average fiber diameter decreased and the diameter variation distribution became narrow.Compared with pure PMMA fibers,the thermal stability of CNC/PMMA composite fibers was significantly improved.When the amount of CNC added was 20%,the glass transition temperature was 120?,and the maximum mass loss was 370?.The mechanical results showed that the tensile strength of the CNC/PMMA fibrous mats with 20 wt%CNCs reached 0.3 MPa.which was 100%higher than that of the pure PMMA nanofibrous mats.The research results provide a theoretical basis for the further study of nanocellulose-reinforced electrospun mats.(2)Furthermore.CNC/PMMA fibrous mats with porous structure were prepared by electrospinning through control of the environmental humidity,and the drug release properties of the porous fibers were explored.The results showed that both PMMA fibers and composite fibers exhibited nanoporous surface formation at high relative humidity.CNC played an important role in accelerating fiber pore evolution and increasing surface roughness.The simulated drug release results showed that the surface porous composite fibers had a higher release rate and release amount.The results revealed the influence mechanism of CNC and environmental humidity on the porous structure and rough surface of fibrous mats and provided a theoretical basis for the preparation of fibrous mats with ideal properties and pore structure by electrospinning.(3)Magnetic cellulose nanocrystals(MCNC)loaded with CoFe2O4 nanoparticles were prepared by in-situ coprecipitation using iron salt and CNC as precursors.MCNC/PLA,CNC/CoFe2O4/PLA nanofibrous mats were successfully prepared by electrospinning.The effects of mixing mode of fillers on mechanical properties,magnetic properties and cytotoxicity of composite fibrous mats were investigated.The SEM results showed that the prepared MCNC/PLA and CNC/CoFe2O4/PLA fibers exhibited uniform distribution and regular morphology.The magnetic particles in the MCNC/PLA fibers were uniformly distributed along the fiber axis,and the agglomerated regions of the magnetic particles were found in the CNC/CoFe2O4/PLA fibers.The magnetic properties analysis showed that the saturation magnetization of MCNC/PLA and CNC/CoFe2O4/PLA nanofibrous mats were 5 emu/g,which showed magnetic hyperthermia under the alternating magnetic field.The MCNC/PLA fibrous mats had a tensile strength of 4.4 MPa,an elongation at break of 80.9%,which superior to that of the CNC/CoFe2O4/PLA fibrous mats.MCNC/PLA fibrous mats exhibited good biocompatibility,while CNC/CoFe2O4/PLA composite fibrous mats had certain cytotoxicity.This study demonstrates the potential application of CNC-based magnetic mats in the field of magnetic thermotherapy.(4)CCN was prepared by a one-step method of ammonium persulfate.The prepared CCN exhibited bundle structure and had high crystallinity of 78.3%.FTIR analysis of CCN showed that carboxyl groups were successfully introduced.CCN-COS was prepared by grafting CCN with Chitosan-oligosaccharide(COS).AgNPs nanocomposites were prepared with CCN and CCN-COS as stabilizers,respectively.The effects of two stabilizers on the morphology,thermal properties,antimicrobial activity and cell compatibility of the composites were studied.Morphology results showed that the average diameters of AgNPs synthesized with CCN and CCN-COS as stabilizers were 31.96 and 16.35 nm,respectively.The thermal stability of CCN-COS-AgNPs was better than that of CCN-AgNPs.The antimicrobial activity of CCN-COS-AgNPs against E.coli,Klebsiella pneumonia and S.aureus was better than that of CCN-AgNPs.In addition,the cytotoxicity of CCN-COS-AgNPs was lower than that of CCN-AgNPs,indicating that CCN-COS as a stabilizer could reduce the deposition of AgNPs.This study provides a theoretical basis for the preparation of nano-silver composites with high antimicrobial properties and low deposition.(5)CCN-COS-Ag/PVA composite mats were prepared by electrospinning using CCN-COS-Ag as antibacterial reinforcing material.The effects of the amount of CCN-COS-Ag on the morphology and properties of the composite fibrous mats were investigated.Microscopic morphology analysis showed that the surface of CCN-COS-Ag/PVA composite fibers exhibited smooth.CCN-COS-Ag were uniformly dispersed in the PVA matrix.The mechanical properties of PVA mats could be significantly improved by adding CCN-COS-Ag.When the content of CCN-COS-Ag was 8%,the tensile strength of composite fibrous mats was 8.6 MPa,which was 90%higher than that of PVA fiber mats.The results showed that the CCN-COS-Ag/PVA nanofiber film exhibited excellent antimicrobial activity against S.aureus and E.coli.When the addition of CCN-COS-Ag was less than 8%,the composite fibrous mats were low toxic and cytocompatible.The composite material had great potential for wound dressing.