The Effects Of Interfacial Properties On The Three Dimensional Confined Assembly Of Block Copolymers/Inorganic Nanoparticles Composites

The confined co-assembly of inorganic nanoparticles（NPs）and block copolymers（BCPs）within emulsion droplets can combine the microphase separation of BCPs and functionality of NPs,resulting in functional organic/inorganic hybrid microparticles,which have broad applications in bioimaging,tumor therapy,photonics and so on.The morphologies of hybrid microparticles have great influence on their performances.For example,the aggregation state of NPs will remarkably affect the performances,such as relaxivity and photo-thermal conversion effect.It was reported that the interfacial properties of oil/water interface dominated the cooperative assembly behavior of BCPs/NPs composites and the morphology of hybrid microparticles under weak confinement.However,the influencing mechanism and regularity of the effect of interfacial properties on the morphologies of hybrid microparticles are still unclear.Furthermore,the responsiveness of BCPs and inorganic NPs to external stimuli can also influence the interfacial properties,as well as the morphologies of hybrid microparticles.Thus,in this dissertation,we focused on the controlling of cooperative assembly of BCPs and inorganic NPs under three-dimensional（3D）confinement by constructing a variety of p H-responsive oil/water interface.We systematically investigated the effect of interfacial properties on the cooperative assembly behaviors of BCPs/NPs composites,and successfully controlled the location of inorganic NPs within hybrid microparticles by utilizing stimuli-responsiveness.As a result,hybrid microparticles with novel morphologies and ordered structures were obtained.The research contents and results are summarized as followed:1.pH-responsive PS-b-PAA grafted iron oxide（Fe₃O₄）NPs were fabricated and utilized as a co-surfactant to control the self-assembly behavior of BCPs under 3D confinement,resulting in hybrid BCPs/NPs microparticles with controlled morphologies.The amount of Fe₃O₄ NPs located on the oil/water interface was carefully controlled to tune the interfacial selectivity of oil/water interface and the morphology of hybrid microparticles.Results showed that Janus pupa-like microparticles were obtained due to the macrophase separation of BCPs and Fe₃O₄ NPs at p H 5.8.As the p H increased,the ionized Fe₃O₄ NPs moved to the interface,changing the oil/water interface to selective interface for PS block and inducing the morphology transition of hybrid microparticles from Janus pupa-like particles to onion-like particles.Furthermore,the hybrid microparticles displayed morphology-dependent relaxivity and the Janus pupa-like microparticles showed a higher relaxivity.2.The interfacial assembly of carboxylated silica（Si O₂-COOH）NPs on the oil-water interface driven by controllable electrostatic interactions between Si O₂-COOH NPs and amino-end homopolymer（PS-NH₂）was utilized to stabilize the dynamic emulsion droplets without adding any surfactants,resulting in BCPs microparticles after the evaporation of solvent.The density of Si O₂-COOH NPs on the oil/water interface was finely controlled by varying the strength of electrostatic interactions between Si O₂-COOH NPs and PS-NH₂.The results showed that the density of Si O₂-COOH NPs assembled on oil/water interface at p H 6.0 was decreased by decreasing the weight fraction of PS-NH₂ and concentration of Si O₂-COOH NPs,leading to BCPs microparticles with regular morphology.Moreover,the interfacial selectivity was finely tuned by simply changing the amino-ended homopolymer and this method can be generally applied to other inorganic NPs.3.Au-Fe₃O₄ hybrid microparticles with well-controlled morphology were fabricated through cooperative assembly of PS grafted Au NPs and PS-b-PAA grafted Fe₃O₄ NPs within emulsion droplets.The results showed that Au NPs moved to the inner space of hybrid microparticles because of the weakened hydrophilicity of Au as the chain length of PS ligand increased.As p H value increased,the hydrophilicity of Fe₃O₄ NPs and the electrostatic attraction between NPs and CTAB surfactants increased,forcing the Fe₃O₄ NPs to move to the oil/water interface.Thus,the arrangement of two kinds of NPs inside the microparticles was finely controlled by tuning the hydrophilicity of NPs and interfacial electrostatic interactions.Furthermore,the properties of as-prepared Au-Fe₃O₄ hybrid microparticles including photo-thermal effect and relaxivity were explored to study the effect of the arrangement of NPs on the performances of hybrid microparticles.4.Hybrid micelles were fabricated through interfacial instabilities of emulsion droplets induced cooperative assembly of amphiphilic BCPs and Fe₃O₄ NPs.The effect of the concentration of surfactant,the weight fraction of NPs and the block ratio of amphiphilic BCPs on the morphology of hybrid micelles and the location of NPs within hybrid micelles were systematically studied.The results showed that the relative size（d/L）of Fe₃O₄ NPs determined whether NPs could move into the micelles.Moreover,this effective method can be applied to load more NPs to prepare multi-functional micelles.Furthermore,the obtained hybrid micelles possessed low cell cytotoxicity and high relaxivity,which may find potential applications in magnetic resonance imaging.