| Polydopamine(PDA)is a melanin polymer material inspired by mussel protein,which has many properties of natural melanin,such as: antioxidant,photothermal effect,selfhealing and adhesion,etc.The adhesion makes it widely used in the field of hydrogels.However,PDA hydrogels have limited application scope due to their low photothermal conversion efficiency and cumbersome preparation methods.The report shows that the iron-containing PDA has an enhanced photothermal effect,which increases the crosssectional area of absorption due to coordination interactions.Therefore,the use of metalchelated polydopamine nanoparticles to modify materials is expected to obtain materials with reliable mechanical properties,electrical conductivity,and photothermal properties,and broaden their application neighborhoods.In this paper,iron ion chelating polydopamine nanoparticles(Fe-PDA NPs)were prepared,and Fe-PDA NPs were used as raw materials to prepare two modified hydrogels,and their properties were studied,which is the basis for hydrogels in melanin biomimetic.Research in the field of materials provides new ideas.The main work of this paper is as follows:1 First,polydopamine nanoparticles(PDA NPs)and iron-doped polydopamine nanoparticles(Fe-PDA NPs)were prepared by a strategy of oxidative self-polymerization and pre-doping of metal ions under alkaline conditions.The morphologies of the two nanoparticles were characterized by scanning electron microscopy(SEM)and transmission electron microscopy(TEM),and then the thermal stability and photothermal effect of the two nanoparticles were analyzed and compared.The results show that the two nanoparticles have regular morphology and uniform particle size distribution.The thermal stability and photothermal effect of Fe-PDA NPs are significantly enhanced compared with PDA NPs,and the photothermal conversion efficiency is as high as 48%.2 Second,the Fe-PDA hydrogel was rapidly prepared at room temperature by utilizing the redox activity of PDA to initiate the polymerization of olefinic monomers.Fe-PDA NPs can not only act as initiators to activate APS to generate free radicals but also act as dynamic cross-linking mediators between polymer chains to promote hydrogel formation.The properties of the hydrogels were then characterized.The results showed that the tensile strength and ductility of the obtained hydrogels vary with the content of Fe-PDA NPs.Hydrogel with 0.15 wt% of Fe-PDA NPs has the highest tensile strength(~0.62 MPa)and hydrogel with 0.6 wt% of Fe-PDA NPs has the highest elongation,about ~650%.The introduction of PDA NPs imparts PAA hydrogel with reproducible adhesive properties and self-healing ability.The doped iron ion further endows hydrogel enhanced photothermal properties and conductivity.3 Finally,the photothermal effect of Fe-PDA NPs was used to prepare shape memory hydrogels,and the properties of hydrogels were analyzed.The results show that PVA/FePDA nanocomposite hydrogels have excellent mechanical properties and photothermal effects,and the mechanical properties are enhanced due to the increase of crystallinity after multiple freezing/thawing.Under NIR irradiation,it not only shows fast shape memory recovery but also has the characteristics of reprogramming and repeated recovery. |
