What Is a PMMA Microsphere?

  • First of all, it is necessary to explain what a magnetic polymer microsphere is. Magnetic polymer microspheres are new functional materials developed in recent years. They are formed by combining inorganic shells with magnetic materials by certain methods. The surface of the polymer shell layer can carry various functional groups by copolymerization, surface modification, and the like, thereby being capable of combining a plurality of active molecules. Since the core is magnetic, the magnetic polymer microspheres can be enriched, separated, recovered, and reused in the presence of an external magnetic field.

    The most important of these is PMMA microspheres (polymethyl methacrylate microspheres). It is a round smooth microsphere with a diameter between 32 and 40 microns, referred to as PMMA microspheres. These magnetic polymer microspheres can be used in many fields, especially in the fields of biological separation and biomedical engineering, such as cell separation, protein separation, immobilized enzymes, and targeted administration. In addition, PMMA microspheres can also be used as implant materials for dentures, lenses, bone cement, etc.

    There are many methods for preparing PMMA microspheres, mainly including:

     Embedding method

     Monomer polymerization method

     Chemical conversion method

    Several important PMMA composite microspheres

    PMMA/SiO2 composite microspheres

    In the nano-silica aqueous dispersion medium, by means of the charge interaction between the cation monomer methacryloyloxyethyltrimethyl chloride (MTC) and the unmodified nano silica particles, by MTC and Strawberry-type PM MA /SiO2 composite microspheres were prepared by free radical copolymerization of methyl methacrylate (MMA). During the whole preparation reaction, nano-silica does not need surface treatment, and no additional emulsifier or co-emulsifier is added in the system. The nano-silica adsorbed on the surface of the microspheres stabilizes the particles. 

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    Fe3O4/PMMA composite microspheres

    Using oleic acid as a surfactant, nano-Fe3O4 with good crystal form and good dispersibility can be prepared by chemical co-precipitation method. Methyl methacrylate (MMA) was used as the reaction monomer, DVB was used as the crosslinking agent, and the magnetic polymer microsphere Fe3O4/PMMA was prepared by the monomer polymerization method using the water-soluble initiator KPS. The magnetic polymer microspheres were obvious. The core-shell structure has a particle size of about 500 nm. MMA is not coated with a single Fe30 nanocrystal, but an aggregate of Fe3O4 nanocrystals. After oleic acid modification, the degree of aggregation of Fe3O4 nanocrystals decreased, and the dispersibility became better, but the shape of the aggregates was still irregular.

     

    PMMA/CS composite microspheres

    Chitosan is derived from a widely used biomaterial chitin, a polysaccharide widely found in crabs and shrimp shells, which has a huge storage capacity in nature. Chitosan has been widely used in the development of nanomaterials, and research on chitosan nanoparticles has become a hot topic, such as embedding, adsorbing drugs, nucleic acids, proteins or enzyme activities. Polymethyl methacrylate (PMMA) is a polymer with an amorphous structure with good mechanical stability and good hardness. Emulsion polymerization of chitosan with PMMA under certain conditions can form core-shell nanoparticles in aqueous solution, which has good mechanical and biocompatibility. It has been experimentally prepared to obtain PMMA/CS core-shell nanospheres without using an emulsifier. In the experiment, the scholars used nitrogen as a protective agent and ammonium persulfate as an initiator to initiate graft copolymerization of methyl methacrylate (MMA) with chitosan to synthesize nanospheres.

     

    RDX/PMMA microspheres

    Hexogeon, the chemical name trimethylene, abbreviated RDX, is a military high-energy explosive.

    RDX/PMMA microspheres can be prepared by using cyclotrimethylene trinitramine (RDX) as the main explosive and polymethyl methacrylate (PMMA) as the binder. Ultrasound-assisted one-step granulation technology can be used. PMMA is a non-toxic and environmentally friendly material with the advantages of smooth surface, small specific gravity, high strength, corrosion resistance and good insulation performance. The high glass transition temperature can be used to improve the mechanical strength of the system. The interaction between PMMA and RDX is stronger and the compatibility is better. It can be used as a binder for RDX coating. Ultrasound-assisted refining and coating one-step granulation technology allowed PMMA to be successfully coated on the surface of RDX.

    The prepared RDX/PMMA particles showed no transformation of RDX/PMMA crystal structure, and the thermal stability and safety performance compared with water suspension The RDX/PMMA particles prepared by the coating technique are all improved. The entire coating process eliminates the RDX refining and drying process, shortens the working time of the ordinary coating by 2.5 times, and improves the working efficiency.