Fluctuation Effects on the Brush Structure of Mixed Brush Nanoparticles in Solution

Journal Article · Thu Jan 18 00:00:00 EST 2018 · ACS Nano

DOI:https://doi.org/10.1021/acsnano.7b08271· OSTI ID:1499037

Koski, Jason P.  ^[1]; Frischknecht, Amalie L.  ^[1]

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1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

A potentially attractive way to control nanoparticle assembly is to graft one or more polymers on the nanoparticle, to control the nanoparticle–nanoparticle interactions. When two immiscible polymers are grafted on the nanoparticle, they can microphase separate to form domains at the nanoparticle surface. Here, we computationally investigate the phase behavior of such binary mixed brush nanoparticles in solution, across a large and experimentally relevant parameter space. Specifically, we calculate the mean-field phase diagram, assuming uniform grafting of the two polymers, as a function of the nanoparticle size relative to the length of the grafted chains, the grafting density, the enthalpic repulsion between the grafted chains, and the solvent quality. We find a variety of phases including a Janus phase and phases with varying numbers of striped domains. Using a nonuniform, random distribution of grafting sites on the nanoparticle instead of the uniform distribution leads to the development of defects in the mixed brush structures. Introducing fluctuations as well leads to increasingly defective structures for the striped phases. Furthermore, we find that the simple Janus phase is preserved in all calculations, even with the introduction of nonuniform grafting and fluctuations. We conclude that the formation of the Janus phase is more realistic experimentally than is the formation of defect-free multivalent mixed brush nanoparticles.

• Research Organization: Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC04-94AL85000
• OSTI ID: 1499037
• Report Number(s): SAND-2019-2234J; 673000
• Journal Information: ACS Nano, Vol. 12, Issue 2; ISSN 1936-0851
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

77 NANOSCIENCE AND NANOTECHNOLOGY
brush structure
field theory
mixed brush
nonuniform grafting
polymer nanocomposites
polymers
thermal fluctuations