# Reactive Polymer Composite Microparticles Based on Glycidyl Metacrylate and Magnetic Nanoparticles
## 1 Introduction  
It is well known that epoxides that have the three-membered ring in their structure can interact with a wide range of reagents to form new valuable products [1]. When epoxy groups are part of insoluble materials (organic, inorganic, hybrid, or composite), their presence allows the materials to be easily modified to obtain new materials with properties tuned to specific applications. For example, glycidyl methacrylate polymers were applied for the immobilization of enzymes [2; 3], as drug transport systems [4; 5], as sorbents in some types of chromatography, for the recovery of metals from aqueous solutions [6; 7], and as catalyst supports [8; 9]. Magnetite (Fe\({}_{3}\)O\({}_{4}\)) nanoparticles also have great research interest due to their potential applications in numerous areas, such as, for example, mineral separation [10], heat transfer [11], electrophotography [12], and different biomedical applications (magnetic resonance imaging (MRI), gene therapy, hyperthermia, chemotherapy, and controlled drug transport) [13; 14; 15; 16; 17; 18; 19]. There are different methods for producing magnetite nanoparticles (MNPs), including co-precipitation, sol-gel, microemulsion, and different thermal and hydrothermal methods [20; 21; 22]. One of the most widely used Fe\({}_{3}\)O\({}_{4}\) synthesis methods, due to its simplicity, is the co-precipitation of Fe(II) and Fe(III) ions from water solutions with a base performed in an inert gas atmosphere [19]. Aqueous solutions of ammonia or sodium hydroxide are most often used for this purpose. Using co-precipitation methods, particles of a wide range of diameters and shapes can be produced depending on the salts used, the ratio of Fe(II) and Fe(III) ions, the ionic strength, temperature, pH reaction mixture, and the stirring speed [20; 21; 22; 23]. To minimize particle sizes and prevent excessive particle agglomeration, chelating compounds are used, such as citric, gluconic, or oleic acids [21]. Unmodified iron oxide MNPs, due to their anisotropic and dipolar properties and their ability to become magnetized, easily aggregate to form large clusters. Therefore, before further use, the surfaces of MNPs are often modified in addition to the use of different chelates [20; 24]. Polymers are characterized by good coating properties, and therefore, they are willingly used in the preparation of magnetic composite materials. Polymer coatings can be used to prevent MNPs from aggregation and agglomeration, increase compatibility between MNPs and the aqueous environment, prevent their surface from oxidizing, reduce toxicity, prevent direct contact of the magnetic substance with the environment, increase colloidal and chemical stability, and facilitate storage or transportation. At the same time, the modification of the iron oxide surface with polymers can expand the scope of the use of materials that have embedded magnetic nanoparticles with completely new applications, such as water purification [25; 26; 27], cell separation and detection [28; 29], proteins, nucleic acids, enzymes [30; 31; 32], and catalyst immobilization [33; 34; 35], as well as in various fields of biotechnology and biomedicine, for example, as systems for targeted drug delivery, DNA isolation, and magnetic hyperthermia targeted drug delivery, and magnetic resonance imaging (MRI) [18; 35; 36; 37; 38]. Polymer magnetic microspheres are macromolecular systems that exhibit the properties of both types of materials. For example, such materials can be isolated easily and quickly using an external magnetic field without the need to use demanding processes such as filtration and centrifugation. The presence of polymers in the composites, in addition to stabilizing MNPs, provides unique physical and chemical properties such as, for example, biocompatibility and reactive functional groups, allowing the composite to undergo further chemical modification to tune the properties of magnetic composites for specific applications. Several methods are used to obtain polymers in the form of particles.