LAUSR

Abstract Nanoparticles govern early (chemical-controlled) and late (diffusion-controlled) stages of epoxy crosslinking, respectively. Surface functionalization of nanoparticles with macromolecules was recognized as an effective route to compensate for inadequate diffusion-controlled crosslinking. However, the effect of bulk composition amended with cations having catalytic effect towards epoxy ring opening has remained hitherto undescribed. In this work, cathodic electrochemical method was applied to obtain naked iron oxide nanoparticles (IONPs), polyethylene glycol (PEG) capped IONPs (PEG-IONPs) and zinc-doped IONPs (Zn-doped PEG-IONPs) for evaluation of the effects of surface (alone) and surface-bulk (concurrent) modification of IONPs. Various techniques including FTIR, XRD, VSM, and FE-SEM were employed to probe into changes in the surface and bulk of nanoparticles. Cure Index calculated based on nonisothermal differential scanning calorimetry (DSC) allowed for labeling epoxy nanocomposites as Poor (Red) or Good (Blue) cured networks. Partial substitution of Fe2+ cations by Zn2+ in the bulk of Zn-doped PEG-IONPs with respect to PEG-IONPs labeled their corresponding epoxy nanocomposites in Blue and Red. Although at low and high heating rates epoxy/PEG-IONPs was labeled Red, epoxy/Zn-doped PEG-IONPs nanocomposites was unconditionally labeled Blue thanks to a more significant catalytic effect springing from Zn2+ cations in Zn-doped IONPs compared to hydroxyl groups alone in PEG-IONPs.