Journal Article

FZJ-2019-06369

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Structure and dynamics in suspensions of soft core-shell colloids in the fluid regime

Pamvouxoglou, A. ; Bogri, P. ; Nägele, G.FZJ* ; Ohno, K. ; Petekidis, G. (Corresponding author)

2019
American Institute of Physics Melville, NY

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Please use a persistent id in citations: http://hdl.handle.net/2128/23704  doi:10.1063/1.5091845

Abstract: We report on a detailed experimental study of the structure and short-time dynamics in fluid-regime suspensions of soft core-shell sphericalparticles with different molecular weights of the chains forming the soft outer shell, and therefore different degrees of particle softness,using 3D dynamic light scattering (3D-DLS). Owing to the particle softness, the liquid-crystal coexistence regime is found to be broader thanthat of hard-sphere (HS) suspensions. Static light scattering in the dilute regime yields form factors that can be described using a sphericalcore-shell model and second virial coefficients A2 > 0 indicative of purely repulsive interactions. The particle-particle interactions are longerranged for all considered systems except those of the smaller molecular weight chain grafted particles which show a HS-like behavior. 3D-DLSexperiments in the concentrated regime up to the liquid-crystal transition provide the short-time diffusion function, D(q), in a broad range ofscattering wavenumbers, q, from which the structural (cage) and short-time self-diffusion coefficients D(qm) and DS = D(q≫qm), respectively,are deduced as functions of the effective particle volume fraction, ϕ = c/c∗, where c∗ is the overlap concentration, calculated using the hydrodynamicparticle radius, RH. The size of the nearest-neighbor cage of particles is characterized by 2π/qm, with D(q) and the static structurefactor S(q) attaining at qm the smallest and largest values, respectively. Experimental data of D(qm) and DS are contrasted with analytic theoreticalpredictions based on a simplifying hydrodynamic radius model where the internal hydrodynamic structure of the core-shell particlesis mapped on a single hydrodynamic radius parameter γ = RH/Reff , for constant direct interactions characterized by an (effective) hard-coreradius Reff . The particle softness is reflected, in particular, in the corresponding shape of the static structure factor, while the mean solvent(Darcy) permeability of the particles related to γ is reflected in the dynamic properties only. For grafted particles with longer polymer chains,D(qm) and DS are indicative of larger permeability values while particles with shorter chains are practically nonpermeable. The particle softnessis also evident in the effective random close packing fraction estimated from the extrapolated zero-value limit of the cage diffusion coefficientD(qm).

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Contributing Institute(s):

1. Weiche Materie (ICS-3)

Research Program(s):

1. 551 - Functional Macromolecules and Complexes (POF3-551) (POF3-551)

Appears in the scientific report 2019

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Database coverage:
; ; Clarivate Analytics Master Journal List ; Current Contents - Physical, Chemical and Earth Sciences ; Ebsco Academic Search ; IF < 5 ; JCR ; NCBI Molecular Biology Database ; National-Konsortium ; Nationallizenz ; PubMed Central ; SCOPUS ; Science Citation Index ; Science Citation Index Expanded ; Web of Science Core Collection

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