Study Of Photo-thermal Dual Response Of Shape Memory Material Enhanced By Nanocellulose

Cellulose is the most abundant natural polymer material on the earth,with many advantages including a wide range of sources,renewability,biodegradability and environmentally friendly and so on.Nano-cellulose prepared from wood fiber raw materials has excellent properties such as large specific surface area,high crystallinity and high strength,and can be used for the enhancement of polymer materials or endowing some new functions.Nano-cellulose(CNC)can be applied to immobilize particles on the surface due to its ability to carry ample hydroxyl groups.In this paper,AuNS/CNC composites were prepared by by a one-step protocol.The obtained gold nanosphere/nanocellolose(AuNS/CNC)composites were then blended with shape-memory polyurethane(SMP)to prepare light-triggered AuNS/CNC/SMP nanocomposites.The effects of AuNS/CNC on the properties of composites films had been studied which lays a foundation both in theory and technique for high-value utilization of CNC.The CNC were isolated from the cotton linters through acid hydrolysis and AuNSs were insitu synthesized in the presence of CNCs under alkaline conditions at room temperature.The effects of reaction conditions on the morphology and diameter of AuNS were investigated.The results showed oxidation of CNC occurred at primary hydroxyl group.Therefore the size and shape of AuNSs depend on concentration of CNC.The higher concentration of CNC,the more the reduction site of the reaction occurs,the smaller diameter of AuNS and the higher of the AuNS monodispersity.While,as the higher pH can weaken the internal and internal hydrogen bonds of the CNC and enhance the reactivity of the hydroxyl groups,the pH value of the experiment mainly affects the reaction rate,the higher the pH value,the faster the reaction rate.The CNC,AuNS,AuNS/CNC composites were then blended with water-soluble polyvinyl alcohol(PVA)respectively to prepare the composites films.Under the condition of ensuring the dispersibility of AuNS,the mechanical properties,photo-thermal properties and transmittance of composite films were investigated.The results show that the mechanical properties of AuNS/CNC/PVA have improved remarkly.Compared with the pure PVA film,the tensile strength is improved by 82.9%,the elastic modulus is increased by 33.2% and the elongation at break is improved by 49.8% due to the existence of CNC in the AuNS/CNC/PVA.Increasing the concentration of nanoparticles proportionally increased the photo-thermal effects if conditions leading to AuNS aggregation were avoided.At the same time,The CNCs played a significant role in the AuNSs/CNC/PVA film by scattering incident light in the film as a secondary light source for AuNS absorbance.Remarkably,the photothermal efficiency of AuNSs in film improved ~ 50% because of CNC,a phenomenon that was enhanced by lower transparency CNCs(higher light scattering point sources).AuNS were prepared by sodium citrate method and gold nanorod(AuNR)with different aspect ratios were prepared by gold seed method.The prepared AuNP/CNC was modified by CTAB and then transferred to organic solvent DMF by solvent conversion method,The modified AuNPCNC nanohybrids were blended with shape-memory polyurethane(SMP)to prepare light-triggered AuNP/CNC/SMP nanocomposites films through solution casting method.The effects of AuNP/CNC on the mechanical properties,thermal properties,photothermal properties and light-trrigered shape memory property of composite films were investigated.The results show that there is a good compatibility between CNC and matrix in the composites.The nanocomposite films were endowed with higher mechanical properties due to the existence of CNC,the maximum tensile strength and tensile modulus of films are increased by 31.79% and 22.73% respectively compared with pure SMP films.The content of AuNSs with existing CNC had a stronger effect on the elevated temperature(?T)and the shapememory properties of films in comparison to the diameter and aspect redio of the AuNSs.At the same time,AuNP/CNC can promote the microphase separation of SMP.Under the corresponding wavelength of laser irradiation,the composite film with a certain content of AuNP/CNC can be restored to the initial shape within 1min,and the recovery rate can reach 100%.