Self-assembly Of Amphiphilic Copolymers And Composite Ag Nanoparticles Based On Microfluidic Technology

Amphiphilic copolymers have attracted people’s attention due to their excellent self-assembly ability and application prospects of their self-assembly products in drug loading,controlled release,and biology.At present,how to control the morphology and size of amphiphilic copolymer self-assembled aggregates has been the focus in this research area.Silver nanoparticles(NPs)have excellent catalytic and bactericidal properties,but silver NPs also has the disadvantage of agglomeration.Therefore,how to prevent silver NPs from agglomeration has an important significance in the application of silver NPs.In this paper,a continuous controlled self-assembly method for amphiphilic copolymers was explored by applying microfluidics technology and combining computational simulations.The microfluidic technology is also applied to prepare composite micelles of silver nanoparticles and amphiphilic copolymers.Amphiphilic block copolymer polyacrylic acid-trifluoroethyl methacrylate(PAA-b-TFEMA)was synthesized via addition-fragmentation chain transfer(RAFT)polymerization,and its self-assembly behavior was researched in the self-made three-dimensional glass capillary microfluidic devices.In order to further explore the influence of mixing kinetics on the self-assembly of block copolymers,software COMSOL Multiphysics was used to simulate the diffusion of two-phase liquids in microfluidics.The simulation and experimental results show that the flow rate of the outer phase can adjust the mixing efficiency of the two-phase streams and the shear rate between laminar flow to adjust the self-assembly of the copolymer.With the increase of the velocity of the outer phase,the size of self-assembled micelles becomes smaller and the distribution becomes wider,and the phenomenon of transition from spherical to other forms occurs.The increase of the total flow rate leads to shorter residence time of the copolymer in the microchannels,and the self-assembled micelles size decreases.Silver NPs were prepared by oxidation-reduction method and hydrophobically modified,then nano-silver particlesthe composited with block copolymers in a microfluidic devices.COMSOL Multiphysics software was used to simulate the diffusion of copolymers and silver nanoparticles in microchannels.The simulation results helped us to choose the microfluidic parameters for co-assembly of Ag and block copolymers.Compared with the traditional solvent-induced method,the microfluidic method promoted silver nanoparticles and block copolymers to co-assemble to form composite micelles.The size of microfluidic devices,modification methods of silver NPs,and flow rates of outer-phase and inner-phase have great effects on the morphology and size of composite micelles.Block copolymers/silver NPs composite micelles with core-shell structure were obtained by controlling microfluidic parameters.In the microfluidic channel with longer length and larger inner diameter,the silver NPs and the copolymer micelles co-assembled better.Amphiphilic gradient copolymers,poly(acrylic acid-trifluoroethyl methacrylate)(PAA-grad-TFEMA),were synthesized by RAFT Polymerization,which composite the silver NPs was studied in microfluidics.The influence of the microfluidic device size,flow rate,solvent type and modification methods on the effect of co-assembly of Ag NPs and gradient copolymers were explored.The results showed that when the flow rate of the outer-phase was 24 mL/h and the flow rate of inner-phase was 3 mL/h,the gradient copolymer and the silver nanoparticles form composite micelles with core-shell structure.TEM results showed that the silver nanoparticles were located in the core of the composite micelles.When the gradient copolymer solution was used as the outer-hase solution and silver nitrate aqueous solution was used as the outer phase solution,the gradient copolymer could form micelles loaded with silver ions through microfluidic self-assembly.Then,the silver ions on the micelles were reduced to obtain composite micelles of the gradient copolymer and silver NPs.This in-situ microfluidic assembly method was more efficient.The solvent type of the inner-phase solution had a significant effect on the structure of the composite micelles.With dioxane as the inner-phase solvent,most silver NPs were loaded on the surface of composite micelles.When tetrahydrofuran was used as the solvent,silver NPs entered the core of composite micelles.