Effects Of Cations On Emulsion Droplets Containing Copolymers And Their Assembled Structures

Self-assembly of diblock copolymer,polystyrene-block-poly(4-vinylpyridine)(PS-b-P4VP),by emulsion-solvent evaporation method has been studied.Three strategies are developed to tune the self-assembly of PS-b-P4 VP in emulsion droplets,which result in the formation of nanostructured particles or micelles with controllable morphologies.Firstly,we demonstrated the p H-depended self-assembly and thereof morphology of PS-b-P4 VP particles in emulsion droplets.Owing to the hydrophobic-hydrophilic transition of P4 VP block induced by protonation,the morphology of PS-b-P4 VP particles transformed from pupa-like to onion-like structure.More interesting,emulsion interfacial instability was observed when p H was further decreased,which resulted in the formation of vesicles,worm-like and spherical micelles.Moreover,the effects of the molecular weight and block ratio of PS-b-P4 VP,the addition of homopolymer PS with varying degree of molecular weight and concentration,temperature and stirring speed during evaporation on the morphology of the particles were systematically studied.In this work,we provide a method by combining the 3D confinement and interfacial instability of emulsion towards the self-assembly block copolymers.Secondly,the self-assembly of PS-b-P4 VP in emulsion droplets in the presence of metal ions(e.g.,Pb(II),Cu(II),and Fe(III))were investigated.Both the packing parameter and the hydrophilicity of P4 VP block changed due to the cooperation interaction between metal ions and P4 VP units.As a result,PS-b-P4 VP particles with varying morphologies from nanostructured particles to micelles were obtained.By changing the molecular weight and block ratio of PS-b-P4 VP,the concentration and type of metal ions,novel morphologies including porous particles and macro-capsules etc.were observed.This study provides a new method to prepare metal/polymer particles or micelles.