Local Structure and Relaxation Dynamics in the Brush of Polymer-Grafted Silica Nanoparticles

Published

June 19, 2018

Author(s)

Yuan Wei, Yifan Xu, Antonio Faraone, Michael J. A. Hore

Abstract

When grafted to spherical nanoparticles at high grafting densities, polymers adopt a variety of conformations. Due to strong confinement by neighboring chains, portions of the polymer near the nanoparticle core are highly stretched in the concentrated polymer brush region (CPB) of the polymer layer. Farther away from the core, where the polymer is less confined, the conformation becomes more ideal in the semi-dilute polymer brush (SDPB) region. Using a combination of small-angle neutron scattering (SANS) and neutron spin echo (NSE) spectroscopy, we directly characterized both the structure and dynamics of the CPB and SDPB on poly(methyl acrylate) (PMA) grafted SiO₂ nanoparticles (NPs). Analysis of SANS measurements using a new core-chain-chain (CCC) model confirmed that that portion of the chain in the CPB region is highly stretched, and transitions to a more random conformation after a cutoff distance τ_c, in agreement with previous theory and experiments. By selectively deuterating the CPB or SDPB, it was possible to separately probe the dynamics of the two regions of the brush for the first time. Dynamics in the CPB region were found to be much slower than the SDPB region, highlighting the strong, pronounced effect that neighboring chains can have on the polymer dynamics of spherical polymer brushes.

Citation

ACS Macro Letters

Volume

7

Issue

6

Pub Type

Journals

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Citation

Wei, Y. , Xu, Y. , Faraone, A. and Hore, M. (2018), Local Structure and Relaxation Dynamics in the Brush of Polymer-Grafted Silica Nanoparticles, ACS Macro Letters, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=925662 (Accessed December 15, 2024)