Preparation And Performance Regulation Of Xylan Nanocomposite Intelligence Hydrogels

As the main components of biomass,xylan-type hemicelluloses have the advantages of abundant resources,low price,and renewable,biodegradable and biocompatible ability.However,the application of hemicelluloses in the field of hydrogel is limited because of its poor gel forming performance caused by inherent defects of heterogeneous structure,low average molecular weight and poor processing performance.Generally,grafting and crosslinking technology is applied to dissolve the problem of poor gel forming performance,but the mechanical properties of xylan hydrogel are still low,limiting the industrial application.In order to broaden the application range of xylan hydrogel,in this study,xylan and its derivatives were used as raw materials,in views of strengthening characteristics of zero-dimensional,one-dimensional and two-dimensional nanomaterials,a series of xylan hydrogels with great mechanical properties and intelligent characteristics were constructed through designing various crosslinked bonds.The enhancement mechanism of nanomaterials and crosslinking methods for hydrogel was studied,and their effects on hydrogel properties were discussed.The potential applications of xylan nanocomposite hydrogel were simply explored.1.Six kinds of zero-dimensional nanoparticles?MgO,ZnO,Al₂O₃,Fe₂O₃,SiO₂ and TiO₂?as nanofiller materials were introduced into carboxymethyl xylan-g-polyacrylamide nanocomposite hydrogel as nanofiller materials.The properties of nanocomposite hydrogels were analyzed by FTIR,XRD,SEM,rheological analysis,swelling analysis and mechanical test.The results showed that the hydroxyl groups on the surface of the nanoparticles formed hydrogen bonds with the amino groups and carboxyl groups in the polymer to improve the mechanical strength of nanocomposite hydrogels.The composite hydrogel with TiO₂ had the maximum compressive strength?508.3 7 kPa?,tensile strength?22.59 kPa?and the longest elongation?784.1%?.The nanocomposite hydrogel could maintain the originated 90%strength after 30 cycles of compressive test.In addition,the nanocomposite hydrogel possessed water-driven shape memory performance.2.The nanocomposite hydrogel was synthesized by introducing one-dimensional acid-treated carbon nanotubes?AT-CNTs?nanomaterials into the maleic anhydride modified xylan grafted with poly?N-isopropylacrylamide?composite hydrogel?MAX-g-PNIPAM?network.The properties of nanocomposite hydrogel were analyzed by FTIR,XRD,SEM,swelling analysis and mechanical test.It was found that AT-CNTs could reinforce the mechanical properties of composite hydrogel,being up to 83 kPa for the compressive strength,which was four times of MAX-g-PNIPAM composite hydrogel without AT-CNTs.Meanwhile,the nanocomposite hydrogel exhibited NIR photothermal conversion properties,and the water temperature in cuvette containing the composite hydrogel was increased 26?to 56?within8 minutes under the NIR irradiation.In addition,the nanocomposite hydrogel possessed shape memory properties driven by the salt solution.3.A highly efficient one-pot strategy was developed to prepare carboxymethyl xylan-g-poly?acrylic acid?nanocomposite hydrogel with high compressive strength,high elongation and high elasticity by using the metal coordination and the reinforcement of one-dimensional hydroxylate multi-walled carbon nanotubes?HCNTs?nanomaterials.The properties of nanocomposite hydrogel were analyzed by FTIR,XRD,SEM,rheological analysis,swelling analysis and mechanical test.The results showed that the Fe³⁺-carboxyl coordination and HCNTs imparted composite hydrogels with high strength and good rapid recovery properties,in which the maximum compressive strength and elongation at break were achieved to 10.34MPa and 1032%respectively,and the shape of composite hydrogel almost returned to the original shape after the external force was removed after 30 cycles of compression.The nanocomposite hydrogels also exhibited Fe³⁺-triggered shape memory properties.4.The xylan nanocomposite hydrogel was prepared by freeze-thaw cycle method using enhancement properties of one-dimensional cellulose nanocrystal?CNC?nanomaterials,the electrostatic interaction between CNC and quaternary ammonium xylan?QAX?and strong hydrogen bonding of polyvinyl alcohol?PVA?.The properties of nanocomposite hydrogel were analyzed by FTIR,XRD,SEM,rheological analysis,swelling analysis and mechanical test.The results showed that the electrostatic interaction between CNC and QAX and the high amount of PVA were favorable to improve the mechanical properties of nanocomposite hydrogel,in which the maximum compressive strength and elongation at break of composite hydrogel were 1.56 MPa and 771%respectively.In addition,the strong hydrogen bonding imparted self-healing characterizes for nanocomposite hydrogel,and the healing efficiency was 37.03%within 48 h.5.Based on the interaction of metal coordination bond and the electrostatic interaction between one-dimensional cellulose nanofibers?CNF?nanomaterials and QAX,the xylan nanocomposite hydrogel was constructed,which possessed with the great mechanical strength and adhesion and rapid self-healing properties.The properties of nanocomposite hydrogel were analyzed by FTIR,XRD,SEM,rheological analysis,swelling analysis and mechanical test.The metal coordination bond between polyacrylic acid and Al³⁺and the electrostatic interaction between CNF and QAX formed a double physical crosslinked structure,which had a positive influence on the mechanical strength of nanocomposite hydrogel,in which the maximum tensile strength and elongation at break of composite hydrogel were 31.03 kPa and2971%,respectively.Meanwhile,the nanocomposite hydrogel exhibited rapid self-healing properties,and the healing efficiency could reach 95%within 2 h.In addition,the nanocomposite hydrogel possessed adhesion and could adhere to metal blocks,glass culture dishes,rubber stoppers,plastic boxes,and human skin.6.Two-dimensional bentonite nanomaterials were used as nanofiller materials to synthesized idopamine-grafted carboxymethyl xylan?CMX-DA?nanocomposite hydrogel.The properties of nanocomposite hydrogel were analyzed by FTIR,XRD,SEM,rheological analysis,swelling analysis and mechanical test.The results showed that bentonite as a nanofiller could promote the mechanical strength of nanocomposite hydrogel,in which the maximum compressive strength,maximum tensile strength and elongation at break of composite hydrogel were 15.06 kPa,218.29 kPa and 435%,respectively.In addition,the catechol of dopamine imparted nanocomposite hydrogel with adhesion properties,and the composite hydrogel could adhere to glass,plastic,metal and PTFE.Six kinds of xylan-based nanocomposite hydrogels with excellent properties were designed.Nanomaterials and the physical and chemical crosslinks endowed xylan hydrogels with high mechanical strength,and intelligent performances such as shape memory,self-healing property and adhesion.The enhancement mechanism of hydrogels was clarified as well as the intelligent mechnisam.This work will provide an important technical support and theoretical knowledge for the high value-added utilization of xylan.