Enhanced Mechanical Property of Polymer Nanocomposites Using Dopamine-Modified Polymers at Nanoparticle Surfaces

The mechanical reinforcement of polymer nanocomposites (PNCs) relies on the microscopic details, typically the particle dispersion in polymer matrix. While chemical grafting method is common, and usually considered to effectively control particle dispersion, this method requires intricate grafting chemistry and experimentally expensive. Here, we report the improved mechanical property of unentangled poly(ethylene glycol) (PEG) can be obtained by employing the dopamine-derived PEG (DOPA-PEG) brush polymers. The DOPA-PEG is easily adsorbed onto silica nanoparticles via strong H-bonding, increasing the effective size of particles in PEG matrix. The microstructure and rheological properties of particles are strongly influenced by the surface coverage density of DOPA-PEG. One intriguing result is that the shear modulus of PNC with DOPA-PEG can be enhanced by 10⁵ times, compared to the PNCs without DOPA-PEGs. The detailed microstructure and rheology are studied by small angle X-ray scattering (SAXS) and oscillatory rheological experiments.