# Reactive Polymer Composite Microparticles Based on Glycidyl Metacrylate and Magnetic Nanoparticles
## 3 Results and Discussion  
### Preparation of Epoxy Functionalized Composite Microparticles  
Suspension polymerization of the monomer composition containing 20 mol% glycidyl methacrylate (GMA), 77 mol% styrene (S), 3 mol% divinylbenzene (DVB), and benzoyl peroxide (BPO, as a polymerization initiator) diluted with a proper organic solvent provided strongly swellable and easily modifiable gel-type polymer microparticles [55]. In this work, magnetite nanoparticles were applied to modify the previously developed procedure and obtain epoxy-functionalized swellable polymer-inorganic composite microparticles (Scheme 1). Hydrophoghed magnetite particles were prepared by precipitating Fe\({}_{3}\)O\({}_{4}\) from the water solution of FeSO\({}_{4}\) -7H\({}_{2}\)O (1 eq.) and FeCl\({}_{3}\) (2 eq.) with ammonia and modifying the surfaces of the initially precipitated particles with oleic acid (OA). Hydrophobic molecules of OA cover the surface of the formed nanoparticles, limit their agglomeration, and allow Fe\({}_{3}\)O\({}_{4}\)@OA particles to be transferred to organic solvents. In this work, toluene was used to obtain Fe\({}_{3}\)O\({}_{4}\)@OA particle fluid. The provided particles were quantitatively transferred to toluene, and the resulting black fluid contained nanosized magnetic particles. Figure 1  
Figure 1 presents the size distribution of the nanoparticles in a fluid sample dispersed in isopropyl alcohol determined using a dynamic light scattering (DSL) technique. The obtained toluene magnetite dispersion was used in an amount of 0.05-0.75 wt.% Fe\({}_{3}\)O\({}_{4}\)@OA by weight with respect to the monomers. To achieve a good swelling capacity of the final composite microparticles and to provide compatibility with Fe\({}_{3}\)O\({}_{4}\)@OA particles, toluene was applied as a diluent for the monomer composition instead of the previously used cyclohexanol/octanol mixture [55, 58]. Initially, polyvinylpyrrolidone K-90 solutions (PVP, 1-3 wt.%) were used as a dispersive medium; however, they did not provide the appropriate conditions to stabilize the suspension of monomer compositions with toluene and Fe\({}_{3}\)O\({}_{4}\)@OA nanoparticles. As a result, it was rather impossible to separate polymer particles from irregularly shaped impurities that also formed abundantly during polymerization. A clear improvement in the form of the polymer particles was observed when the PVP solutions were replaced by poly(vinyl alcohol) (PVA, 1 wt.%) solution. The polymerization conditions were then optimized by changing the ratios of water to organic phases and toluene to monomers. The best results were obtained for the ratios of 8:1 and 2:1, respectively. For these conditions, a series of polymerization experiments were performed in which the concentration of Fe\({}_{3}\)O\({}_{4}\)@OA and the stirring rate were changed. The brownish particles provided as a result were characterized by the broad size dispersity compared to products of classical suspension polymerization (Table 1). Furthermore, the average diameter of the particles increased by approximately 60 \(\upmu\)m when only 0.05 wt.% Fe\({}_{3}\)O\({}_{4}\)@OA was added to the monomer composition (Figure 2, Table 1, entry 2). An increase in the amount of Fe\({}_{3}\)O\({}_{4}\)@OA to 0.25 wt.% entailed a further increase in the average diameter of the polymer particles (Table 1, entry 4). It also resulted in an increase in the dispersity of the particle size. Further doubling the concentration of Fe\({}_{3}\)O\({}_{4}\)@OA (Table 1, entry 5) caused a decrease in the average diameter of the final polymer particles. However, this factor did not have a substantial influence on the particle size distribution. A slight increase in the particle diameter and a decrease in dispersity was observed when 0.75 wt.% Fe\({}_{3}\)O\({}_{4}\)@OA was used (Table 1, entry 6). A similar effect was obtained by increasing the stirring rate from 350 to 500 rpm (Figure 3, Table 1, entry 7).