Enhanced Mechanical Properties of Polymer Nanocomposites Using Dopamine-Modified Polymers at Nanoparticle Surfaces in Very Low Molecular Weight Polymers

Abstract

While incorporation of nanoparticles (nanofillers) into polymer matrices is well-known as one of the methods to improve the mechanical properties of polymers, it is still challenged to enhance mechanical properties in very low molecular weight polymers like as those in high molecular weight. Here, we report the dramatically enhanced mechanical properties of very low and unentangled poly(ethylene glycol) (PEG) can be obtained by employing the dopamine-modified PEG (DOPA-mPEG) brush polymers as a physical grafting agent on silica nanoparticle surfaces. We found DOPA-mPEG grafting on silica surface can i) increase effective particle volume of particles in PEG matrix, ii) form suprastructures with particle aggregations, and ii) enhance the shear modulus of PEG by a factor of 105 at an appropriate surface grafting density. Extensive small-angle X-ray scattering, and oscillatory shear experiments were performed to investigate the detailed microstructure and rheological properties.