When grafted to spherical nanoparticles, polymers can adopt a variety of conformations depending on the nanoparticle size and polymer grafting density. At moderate grafting densities, a high concentration of polymer near the nanoparticle (“concentrated polymer brush”, CPB region) core creates confinement effects that cause the polymer chain to be stretched, with a thickness that scales with the degree of polymerization (N) as h ~ N0.8. Past a cutoff distance rc, that can be calculated by scaling theories, the concentration decreases with increasing distance from the core (“semi-dilute polymer brush”, SDPB region) and the polymer chain adopts a more random conformation. In this talk, we discuss recent progress in characterizing the structure and dynamics of polymers that are grafted to spherical nanoparticles by small-angle neutron scattering (SANS) and neutron spin echo spectroscopy (NSE), respectively. New core-shell-chain (CSC) and core-chain-chain (CCC) form factors, which account for excluded volume in the polymer chains, are able to capture the predictions from scaling theories, and are in good agreement with scaling relationships observed from dynamic light scattering (DLS) and electron micrograph analysis. NSE measurements show that the confinement experienced in the CPB region can have a significant impact on the relaxation dynamics of the polymers, which may in turn have implications for the processing and mechanical properties of nanocomposites containing such particles.

Local structure and relaxation dynamics in the brush of polymer-grafted nanoparticles

256th National Meeting (2018)

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