Preparation And Morphological Control Of Anisotropic Particles Via Seeded Emulsion Polymerization

Anisotropic particles generally refer to a kind of special colloidal particles with non-uniformity and asymmetry in physical morphology and structure or chemical composition.Because of their special properties in morphology,structure and functional composition,as well as their application prospects in the fields of physics,chemistry and biology,anisotropic particles,anisotropic particles have attracted the interest of researchers in the design of multifunctional particle emulsifiers,heterogeneous catalysts and self-driven nanomotors.In order to meet the application requirements and broaden the application field of anisotropic particles,it is very important to design,scale,modify and functionalize the anisotropic particles in the preparation process.Among the many methods to prepare anisotropic particles,seeded emulsion polymerization has attracted the attention of researchers in related fields because of its simple operation,strong design ability and the ability to achieve mass production of particles.However,in terms of the diversity of morphology regulation and the convenience of further modification and functionalization,the seeded emulsion polymerization systems constructed by relevant work at present still have some limitations.Therefore,if functional materials are introduced into this method to directly prepare complex particles with functional properties,the structural advantages of anisotropic particles can be combined with the functional properties of materials,and it is more convenient and efficient than traditional post-modification methods.In this paper,anisotropic particles containing functional groups were prepared by seed emulsion polymerization method.By changing the experimental parameters in the preparation process,the interfacial tension and compatibility between the phases were changed,so as to realize the morphology control on the basis of scale and functionalization.The specific research contents are as follows:(1)Study on preparation and morphology control of PVBC-Silica Janus type anisotropic particles.First,4-vinylbenzyl chloride(VBC)was used as monomer to obtain poly(4-vinylbenzyl chloride)(PVBC)seed particle through dispersion polymerization.Then,PVBC-Silica Janus particles with one side organic polymer PVBC and the other side inorganic Silica were prepared by seeded emulsion polymerization using PVBC as the seed and 3-(methylacrylloxy)propyltrimethoxy silane(MPS)as the polymeric monomer.Scanning electron microscopy(SEM),Transmission electron microscopy(TEM),Infrared analysis(IR),particle size analysis(DLS)and other characterization methods were used to analyze the structure and morphology of particles.The method and mechanism of controlling the morphology of anisotropic particles were investigated by changing the amount of MPS monomer,the amount and type of co-solvents,the p H value of the reaction system and the degree of crosslinking of seeds.The results showed that,within a certain range,the size of Silica ball increased with the increase of MPS amount,but too many secondary particles formed when the Silica exceeded the range.With the addition of co-solvent ethanol,PVBC-Silica particles gradually changed from core-shell to snowman and dumbbell Janus particles,and finally changed into Patchy particles with PVBC as core and PVBC as patchs.When the reaction system was more alkaline,the hydrolysis and condensation rates of siloxane were fast,which resulted in the formation of anisotropic particles with PVBC as core and Silica as patches.However,when the reaction system was more acidic,the hydrolysis rate of siloxane increased and the condensation rate decreased,which resulted in the formation of anisotropic particles with PVBC as core and Silica as patches.Different kinds of co-solvents also lead to changes in the morphology of particles due to their different polarity and molecular weight,because the polarity will affect the agglomeration of products,and the level of molecular weight will affect their ability to form hydrogen bonds in water and steric hindrance,which will lead to changes in the hydrolysis and condensation rate of organic silicon.In addition,the PVBC ball of Janus particle was cross-linked by Friedel-crafts reaction to improve the solvent resistance and emulsification performance.At the same time,a large number of benzyl chlorine groups were still retained on the particles,which could be used for further surface modification.(2)Study on preparation and morphology control of Patchy type anisotropic particles.First,the polymethyl methacrylate(PMMA)seed particles were prepared by emulsion polymerization with methyl methacrylate(MMA)as monomer.Polymerizable ionic liquid(IL)monomer [MTMA][TFSA] was synthesized by anion exchange using methyl acrylloxyethyl trimethylammonium chloride([MTMA]Cl)and bis(trifluoro-methonyl)lithium-imide(Li[TFSA]).Next,PMMA was used as the seed,[MTMA] [TFSA] was used as the monomer,and the aqueous solution of nonionic surfactant nonylphenol polyoxyethylene ether(NP-40)was used as the reaction medium to prepare PMMA-PIL Patchy particles by seeded emulsion polymerization.The structure and morphology were analyzed by SEM,IR,DLS and DSC.By changing the amount of NP-40 and IL monomers in the preparation process,the method and mechanism of morphology control of anisotropic particles were explored.The results show that within a certain range,the number of PIL patches increases with the increase of the amount of NP-40,but beyond the range,PIL will coat on the surface of the particle as a whole.Increasing the amount of IL monomer will lead to a decrease in the number of PIL patches,and this morphological regulation is universal,which is applicable to PMMA seed particles of different size.In addition,PMMA-PIL Patchy particles can be used as particle emulsifier.Compared with PMMA particles,the emulsification performance of PMMA-PIL Patchy particles is significantly improved,and a more stable Pickering emulsion can be constructed.