Preparation and properties of photopolymerized hybrid composites with covalently attached magnetite nanoparticles

Using magnetite nanoparticles (50-100 nm) containing methacrylic groups (MNPs-MA or shortly, M) as inorganic phase into a mixture of photopolymerizable monomers with and without acid moieties in structure, a series of hybrid nanocomposites were prepared and characterized by FTIR, TEM, SEM-EDX analysis, and magnetization studies. For this purpose, two diacrylates based on castor oil triglyceride functionalized with carboxyl (CO-DAC) or phosphate (CO-DAP) groups were synthesized and incorporated in formulations besides urethane dimethacrylate (DMUO-1) and triethylene glycol dimethacrylate. Kinetic data obtained for photopolymerization in the presence of Irgacure 819, revealed that the maximum polymerization rate (RPmax) and the conversion degree (DC) are dependent on the monomer structure and the formulation composition. For instance, the inclusion of 0.1 wt.% M had as result a slight decrease of RPmax from 0.088 s−1 (F1/30 wt.% CO-DAP) to 0.075 s−1 (F1-0.1 M), the highest value being found in the non-acid F3 formulation (0.1155 s−1). When the amount of nanoparticles increased to 1.0 wt.%, the RPmax, DC, gel content and mechanical characteristics of the hybrid films were influenced in a different manner. TEM and SEM-EDX analysis confirm a good dispersion of nanoparticles in the organic matrix containing CO-DAC or CO-DAP monomer units, compared to the effect of crowded structure observed in the composite with no acid groups. Specifically, the magnetic hysteresis (Ms) loops indicated a ferromagnetic behavior for these composites, for which the saturation magnetization amplified with increasing amount of nanoparticles in the sample (from 37.85 emu/g for F1-0.1 M to 45.31 emu/g for F1-1.0 M).