In-Situ Composite Of Ag Nanoparticles And Gradient Copolymers In Microfluidics

Silver nanoparticles(Ag NPs)have important application value in the fields of catalysis,antibacterial,etc.,but Ag NPs have the problem of easy agglomeration.Loading Ag NPs on polymer micelles is an effective method to solve the problem of easy agglomeration of Ag NPs.The gradient copolymer micelles have more pronounced stimuli responsiveness relative to the block copolymer,so the amphiphilic gradient copolymer-Ag NPs composite micelles will have more unique properties.Compared with traditional solvent-induced self-assembly methods,microfluidic self-assembly technology can control the morphology and size of micelles more precisely.Therefore,in the microfluidic device,based on the in-situ reduction mechanism,a "two-step method" and a "one-step method" were respectively used to prepare composite micelles of Ag NPs and gradient copolymers in this study.In the second chapter,the gradient copolymer-Ag NPs composite micelles were prepared by the "two-step method".First,the dioxane solution of the acrylic acid-trifluoroethyl methacrylate gradient copolymer was used as the internal phase fluid,the aqueous solution of silver nitrate is the external phase fluid,and the gradient copolymer-silver ion composite micelles were obtained in the microfluidic channel.After the composite micelles were discharged from the tube,sodium borohydride was added dropwise to the composite micelle solution,and the silver ions loaded on the composite micelles were reduced to Ag NPs,and finally a gradient copolymer-Ag NPs composite micelles were obtained.The morphology and size of the composite micelles were characterized by transmission electron microscopy(TEM)and dynamic light scattering(DLS).The effects of microfluidic fluid parameters and silver nitrate dosage on the morphology and size of the composite micelles were discussed.The results show that the shape of the composite micelles is mainly spherical,and the loaded Ag NPs are located in the hydrophilic shell of the micelles.As the flow rate of the external phase increases,the size of the composite micelles becomes smaller,the density of Ag NPs on the micelles decreases,and non-spherical micelles appear.As the amount of silver nitrate in the external phase fluid decreases,the average size of the composite micelles decreases,the density of Ag NPs on the composite micellesdecreases,and the average size of the Ag NPs increases.In the third chapter,the gradient copolymer-Ag NPs composite micelles were prepared by the "one-step method".The dioxane solution of the gradient copolymer containing sodium borohydride was used as an internal phase fluid,and an aqueous solution of silver nitrate was the external phase fluid.In the microfluidic device,the co-assembly of the gradient copolymer and the silver ion and the reduction of the silver ions were simultaneously performed,and the gradient copolymer-Ag NPs composite micelles were directly obtained after the fluid was discharged from the tube.The morphology and size of the composite micelles were characterized by TEM and DLS.The effects of microfluidic fluid parameters and silver nitrate dosage on the morphology and size of the composite micelles were discussed.The results show that the gradient copolymer-Ag NPs composite micelles with shell-loaded Ag NPs can be prepared by one-step method.As the flow rate of the external phase increases,the size of the composite micelles gradually decreases,the density of loaded Ag NPs gradually decreases,the size of the loaded Ag NPs gradually increases,and the amount of free Ag NPs gradually increases.With the decrease of the amount of silver nitrate,the density of Ag NPs loaded on the composite micelles gradually decreases,the size of Ag NPs loaded on the composite micelle gradually increases,and the size of the composite micelles gradually decreases.