Covalently integrated silica nanoparticles in poly(ethylene glycol)-based acrylate resins: thermomechanical, swelling, and morphological behavior.

Nanocomposites integrate functional nanofillers into viscoelastic matrices for electronics, lightweight structural materials, and tissue engineering. Herein, the effect of methacrylate-functionalized (MA-SiO) and vinyl-functionalized (V-SiO) silica nanoparticles on the thermal, mechanical, physical, and morphological characteristics of poly(ethylene glycol) (PEG) nanocomposites was investigated. The gel fraction of V-SiO composites decreases upon addition of 3.8 wt% but increases with further addition (>7.4 wt%) until it reaches a plateau at 10.7 wt%. The MA-SiO induced no significant changes in gel fraction and both V-SiO and MA-SiO nanoparticles had a negligible impact on the nanocomposite glass transition temperature and water absorption. The Young's modulus and ultimate compressive stress increased with increasing nanoparticle concentration for both nanoparticles. Due to the higher crosslink density, MA-SiO composites reached a maximum mechanical stress at a concentration of 7.4 wt%, while V-SiO composites reached a maximum at a concentration of 10.7 wt%. Scanning electron microscopy, transmission electron microscopy, and small-angle X-ray scattering revealed a bimodal size distribution for V-SiO and a monomodal size distribution for MA-SiO. Although aggregates were observed for both nanoparticle surface treatments, V-SiO dispersion was poor while MA-SiO were generally well-dispersed. These findings lay the framework for silica nanofillers in PEG-based nanocomposites for advanced manufacturing applications.