Elucidating the Roles of Grafting Density and Bonding Types on the Tethered Polymer Dynamics in Nanoparticle Organic Hybrid Material System

In this study, molecular dynamics and structure of nanoparticle organic hybrid material (NOHMs) system comprising silica nanoparticle-tethered polyetheramine were

investigated by broadband dielectric spectroscopy (BDS), X-ray scattering (SAXS), and thermal analysis techniques (TGA and DSC). Grafting density and chemical bonding

(ionic and covalent) are controlled during the synthesis process to understand the effect of these parameters on the structure and molecular dynamics of NOHMs. Thermal

analysis showed that covalently bonded samples have higher thermal stability and glass transition temperature (Tg) than ionic counterparts. The Tg is enhanced by increasing

grafting density in both ionic and covalent NOHMs. With decreasing grafting density, the SAXS characteristic peak shift to higher q values revealing center-to-center interparticle distance reduction. Dielectric spectroscopy results revealed the slowing down of -relaxation time is controlled by grafting density and bonding so that higher relaxation time is obtained in the highly grafted sample with the covalent bond. Broadening the relaxation time distribution implied heterogeneous structural dynamics governed by grafting density and bonding type. These results demonstrate the role of grafting density and bonding types on the rational design of NOHMs for desired properties