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 (R-max(P)) 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 R-max(P) 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 R-max(P), 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 (M-s) 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). (C) 2014 Elsevier B.V. All rights reserved.