The Mechanism On The Formation Of Multihollow Polymer Spheres Through Sulfonated Polystyrene Particles

Multihollow microspheres have been intensively studied and widely used because of their low density and high specific surface, such materials have potential applications in drug storage and controlled release, efficient encapsulation of active ingredients (such as proteins), selective separation, catalyst supports, ion exchangers, sensors, electrorheological properties, solar cells, mimicking photosynthesis, optical applications, and so on. Thus the preparation of multihollow microspheres has been intensively explored by material scientists. Recently, the self-assembly of monodisperse latex particles at emulsion droplet interface and subsequent-fixing with a composite layer to form multihollow microcapsules was studied with the further understanding on the theories of the colloid and interface chemistry and the development of self-assembly and emulsion morphology controlling technique.In this paper, we first carried out a comprehensive and systematic research work on the self-assembly behaviors of sulfonated polystyrene (SP) at oil/water interface under different dispersing conditions. It was found that there were two different kinds of self-assembly processes, thereout two different multihollow polymer spheres were obtained. The mechanism on formation of multihollow polymer microsphere had been discussed in detail. Finally, we established a simple and effective route to achieve the porous polymer microspheres with various morphologies and controlled pore size at the presence of the SP microsphere as the template.The main results of this thesis are summarized as follows:1. SP particles were first located in MMA, Then it was emulsified with water, and stable multiple emulsions could be prepared simply. After initiating the polymerization of MMA by 60Coγ-ray radiation, the multihollow PMMA particles were successfully fabricated. Based on a series of studies on the formation process of multiple emulsions and the morphology of final porous polymer microspheres with the aid of SEM, OM, etc, a mechanism on the formation of the holes through multiple emulsions was proposed: When SP particles located in MMA first, the SP particles would slowly dissolve in MMA to form polymer emulsifier due to amphipathic molecule chain, then, multiple emulsions were formed. When polymeric monomers with functional groupls (itaconic acid) were added in water, the functionalization multihollow microsphere could be fabricated by this mechanism. 2. SP particles were first located in water, then it was emulsified with MMA monomer, another kind stable emulsion (Pickering emulsion) was prepared simply. After initiating the polymerization of MMA by 60Coγ-ray radiation, cage-like multihollow polymer particles were successfully fabricated. Based on a series of studies on the formation process of pickering emulsions and the morphology of final porous polymer microspheres by the aid of OM,SEM, etc, a mechanism on the formation of the cage-like multihollow polymer microsphere was summarized finally: When SP particles located in water first, the SP particles would be swelled after emulsification but can't dissolved, a Pickering emulsion was formed firstly. After some time, the swelling of SP particles and the reducing of oil droplet would lead to breakage of the Pickering emulsion, then, the SP particles took place a series of swelled-dissolution process, becoming a 3D template. At the same time, with the help of water osmotic pressure which is due to the hydrophilicity of oil phase and sulfonate groups, after polymerization, the porous polystyrene microsphere was successfully obtained.3. Under the guidance of the mechanism on the formation of the cage-like multihollow polymer microsphere, the porous polystyrene microsphere with various morphologies and controlled pore sizes were successfully obtained. The influential factors on the morphology of the final latex partickes includes the size of SP particles, the molecular weight of PS particles, the ratio and polarity of polar solvent in oil phase, and the hydrophilicity of oil phase, etc were discussed in detail. This work provides versatility in the study of the preparation of multihollow polymer microsphere with controlled pore sizes.