Designs And Preparations Of Anisotropic Colloidal Particles

Anisotropic colloidal particles are novel colloidal materials with asymmetric physical or chemical properties.In both fundamental research and technical applications,anisotropic colloidal particles are of great concern.Among the numerous anisotropic colloidal particles,the concave particles have attracted great attentions in the field of colloidal materials in recent years.This is because the concave shape of particles with special morphology that has a huge potential application in the colloidal crystal formation,particle orientation self-assembly,targeted combination,and other fields.Although there are several methods for the synthesis of concave shape colloidal particles,it still exist many problems,such as complex synthetic procedure and low production.Especially the control of particle degree of concave remains a challenge,which greatly limits its application.Therefore,new preparation methods for synthesis of anisotropic concave colloidal particles are needed.We propose a facile method to synthesize polymeric particles with well-controlled concave shape.Our method takes advantage of the powerful seed emulsion polymerization strategy with the well-known principle of "like dissolves like" in solvent chemistry.We first prepare polystyrene(PS)particle with one single dimple by seeded emulsion polymerization.Then the dimpled PS particles were dispersed in a dimethylformamide(DMF)and Water mixture.Consequently,the non-crosslinked polymer chains inside the particle were dissolved by DMF,a good solvent for PS,and the PS chains migrated out of the particle,causing buckling of the dimple and enlargement of the concave.By systematic change of the fraction of DMF in the solvent mixture,we changed the amount of the dissolved PS chains,and achieved polymeric particles with precisely tuned degree of concaveness.These concave particles were found to readily self-assemble when adding polymer-induced depletion interaction.The concave polymeric particles reported here provide potential building-blocks for self-assembled polymeric materials,and new model systems for condensed matter research.In addition,a simple method based on seed emulsion polymerization is designed to design and prepare a new type of organic and inorganic composite bowl-shaped colloidal particles.Materials used in the experiment,ferric oxide particles and organic silane,are common raw material,and the method is easy to realize and have high yield.The feature of the bowl-like particle is its larger cavity,which could be adjusted by stirring speed and the addition amount of the organic silane.Large size bowl makes the new particles can load lots of functional micro-nano particles with many kinds of size and shape.Meantime,the introduction of magnetic materials may also make the composite particles have magnetic control,which is worth to study in the future.