Self-assemble Of Amphiphilic Diblock Copolymer/Asymmetric Nanoparticles In Dilute Solution

Asymmetric nanoparticles have unique physical and chemical properties due totheirspecial characteristics structure. The self-assembly properties of amphiphilic diblockcopolymers in dilute solution and their applications in fabricating the nanomaterials haveattracted more attention. At the same time the self-assemblied structures of amphiphilic diblockcopolymers can be used to control the spatial distribution of nanoparticles. Therefore, newaggregation structures may be obtained by the self-assembly of the amphiphilic diblockcopolymer and asymmetric nanoparticles, which provides a good research platform to improvethe performance of composite materials. Till now, although there have been a number ofresearch papers about the preparation methods of asymmetry nanoparticles, studies on thecoassembly of block copolymers and asymmetric nanoparticles in dilute solution is relativelyfew. This paper mainly discussed the self-assembly of amphiphilic diblock copolymers ofpolystyrene-b-polyacrylic acid （PS-PAA） and inorganic dumbbell-like nanoparticles Au-Fe₃O₄in THF/1,4-Dioxane system.（1） Dumb-bell like Au-Fe₃O₄nanoparticles with average diameter of15nm weresynthesized. The Au-Fe₃O₄nanoparticles covered with oleic acid and oil amine were modifiedwith monocarboxy terminated polystyrene （PS-COOH）. The self-assembly of block copolymerPS-PAA and PS-COOH modified Au-Fe₃O₄nanoparticles in THF/1,4-Dioxane was studied,and the interactions between asymmetric nanoparticles and amphiphilic diblock copolymer indilute solution was mainly considered. When the mass ratio of Au-Fe₃O₄to PS-PAA reached16.0%, PS-PAA and PS-COOH modified nanoparticles can self-assembly intoinorganic-organic composite aggregates.（2） Usually spherical micelles composed of a PS core and a PAA corona were obtained ifamphiphilic diblock copolymer （PS-PAA） assemblied in THF/1,4-Dioxane mixed system. inthis work, a composite micelle structures composed of a PAA shell and a middle PS core, andalways with a cavity throughout PS phase. So we discussed the formation mechanism of thecomposite micelle. it was found from the experiment results that temperature was one of mainfactors influencing formation of composite micelles. Before dialysis, PS in mixed solvents is inthe swollen state. with the process of dialysis, the organic solvent was gradually replaced by ultra pure water, PS changed gradually from the swollen state to the glass state, and the volumeshrinkage. At low temperature （17°C）, the PS blocks reach to the glass state in advance due tothe change of solvent concentration rather than the completely uniform shrinkage of PS blocks,thus forming a cavity in the micelle interior. While the temperature is high, PS can uniformcontraction and the ordinary micellar structures form before reaching glass state.