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Title: Focus: Structure and dynamics of the interfacial layer in polymer nanocomposites with attractive interactions

Abstract

In recent years it has become clear that the interfacial layer formed around nanoparticles in polymer nanocomposites (PNCs) is critical for controlling their macroscopic properties. The interfacial layer occupies a significant volume fraction of the polymer matrix in PNCs and creates strong intrinsic heterogeneity in their structure and dynamics. In this paper, we focus on analysis of the structure and dynamics of the interfacial region in model PNCs with well-dispersed, spherical nanoparticles with attractive interactions. First, we discuss several experimental techniques that provide structural and dynamic information on the interfacial region in PNCs. Then, we discuss the role of various microscopic parameters in controlling structure and dynamics of the interfacial layer. The analysis presented emphasizes the importance of the polymer-nanoparticle interactions for the slowing down dynamics in the interfacial region, while the thickness of the interfacial layer appears to be dependent on chain rigidity, and has been shown to increase with cooling upon approaching the glass transition. Aside from chain rigidity and polymer-nanoparticle interactions, the interfacial layer properties are also affected by the molecular weight of the polymer and the size of the nanoparticles. Finally, in the last part of this focus article, we emphasize the important challenges in themore » field of polymer nanocomposites and a potential analogy with the behavior observed in thin films.« less

Authors:
ORCiD logo [1];  [2];  [1];  [3]; ORCiD logo [3]; ORCiD logo [4]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division
  2. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Physics and Astronomy
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences. Computer Science and Mathematics Division
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division; Univ. of Tennessee, Knoxville, TN (United States). Dept. of Physics and Astronomy
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1376456
Grant/Contract Number:
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 146; Journal Issue: 20; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Polymers; Nanoparticles; Interfacial properties; Interface dynamics; Nanocomposites

Citation Formats

Cheng, Shiwang, Carroll, Bobby, Bocharova, Vera, Carrillo, Jan-Michael, Sumpter, Bobby G., and Sokolov, Alexei P. Focus: Structure and dynamics of the interfacial layer in polymer nanocomposites with attractive interactions. United States: N. p., 2017. Web. doi:10.1063/1.4978504.
Cheng, Shiwang, Carroll, Bobby, Bocharova, Vera, Carrillo, Jan-Michael, Sumpter, Bobby G., & Sokolov, Alexei P. Focus: Structure and dynamics of the interfacial layer in polymer nanocomposites with attractive interactions. United States. doi:10.1063/1.4978504.
Cheng, Shiwang, Carroll, Bobby, Bocharova, Vera, Carrillo, Jan-Michael, Sumpter, Bobby G., and Sokolov, Alexei P. Thu . "Focus: Structure and dynamics of the interfacial layer in polymer nanocomposites with attractive interactions". United States. doi:10.1063/1.4978504. https://www.osti.gov/servlets/purl/1376456.
@article{osti_1376456,
title = {Focus: Structure and dynamics of the interfacial layer in polymer nanocomposites with attractive interactions},
author = {Cheng, Shiwang and Carroll, Bobby and Bocharova, Vera and Carrillo, Jan-Michael and Sumpter, Bobby G. and Sokolov, Alexei P.},
abstractNote = {In recent years it has become clear that the interfacial layer formed around nanoparticles in polymer nanocomposites (PNCs) is critical for controlling their macroscopic properties. The interfacial layer occupies a significant volume fraction of the polymer matrix in PNCs and creates strong intrinsic heterogeneity in their structure and dynamics. In this paper, we focus on analysis of the structure and dynamics of the interfacial region in model PNCs with well-dispersed, spherical nanoparticles with attractive interactions. First, we discuss several experimental techniques that provide structural and dynamic information on the interfacial region in PNCs. Then, we discuss the role of various microscopic parameters in controlling structure and dynamics of the interfacial layer. The analysis presented emphasizes the importance of the polymer-nanoparticle interactions for the slowing down dynamics in the interfacial region, while the thickness of the interfacial layer appears to be dependent on chain rigidity, and has been shown to increase with cooling upon approaching the glass transition. Aside from chain rigidity and polymer-nanoparticle interactions, the interfacial layer properties are also affected by the molecular weight of the polymer and the size of the nanoparticles. Finally, in the last part of this focus article, we emphasize the important challenges in the field of polymer nanocomposites and a potential analogy with the behavior observed in thin films.},
doi = {10.1063/1.4978504},
journal = {Journal of Chemical Physics},
number = 20,
volume = 146,
place = {United States},
year = {Thu Mar 30 00:00:00 EDT 2017},
month = {Thu Mar 30 00:00:00 EDT 2017}
}

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Cited by: 3works
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  • The effect of large deformation on the chain dynamics in attractive polymer nanocomposites was investigated using neutron scattering techniques. Quasielastic neutron backscattering measurements reveal a substantial reduction of polymer mobility in the presence of attractive, well-dispersed nanoparticles. Additionally, large deformations are observed to cause a further slowing down of the Rouse rates at high particle loadings, where the interparticle spacings are slightly smaller than the chain dimensions, i.e. in the strongly confined state. No noticeable change, however, was observed for a lightly confined system. The reptation tube diameter, measured by neutron spin echo, remained unchanged after shear, suggesting that themore » level of chain-chain entanglements is not significantly affected. The shearinduced changes in the interparticle bridging reflects on the slow nanoparticle motion measured by X-ray photon correlation spectroscopy. These results provide a first step for understanding how large shear can significantly affect the segmental motion in nanocomposites and open up new opportunities for designing mechanically responsive soft materials.« less
  • It is generally believed that the strength of the polymer nanoparticle interaction controls the modification of near-interface segmental mobility in polymer nanocomposites (PNCs). However, little is known about the effect of covalent bonding on the segmental dynamics and glass transition of matrix-free polymer-grafted nanoparticles (PGNs), especially when compared to PNCs. In this article, we directly compare the static and dynamic properties of poly(2-vinylpyridine)/silica-based nanocomposites with polymer chains either physically adsorbed (PNCs) or covalently bonded (PGNs) to identical silica nanoparticles (RNP = 12.5 nm) for three different molecular weight (MW) systems. Interestingly, when the MW of the matrix is as lowmore » as 6 kg/mol (RNP/Rg = 5.4) or as high as 140 kg/mol (RNP/Rg= 1.13), both small-angle X-ray scattering and broadband dielectric spectroscopy show similar static and dynamic properties for PNCs and PGNs. However, for the intermediate MW of 18 kg/mol (RNP/Rg = 3.16), the difference between physical adsorption and covalent bonding can be clearly identified in the static and dynamic properties of the interfacial layer. We ascribe the differences in the interfacial properties of PNCs and PGNs to changes in chain stretching, as quantified by self-consistent field theory calculations. These results demonstrate that the dynamic suppression at the interface is affected by the chain stretching; that is, it depends on the anisotropy of the segmental conformations, more so than the strength of the interaction, which suggests that the interfacial dynamics can be effectively tuned by the degree of stretching a parameter accessible from the MW or grafting density.« less
  • In this paper, we explore the thermodynamic and dynamic properties of polymer nanocomposites using Stochastic Molecular Dynamics simulation in the canonical ensemble. One of the major parameters that determines the properties of nanocomposites is the filler-monomer interfacial interaction strengths. By varying the interaction strengths as well as temperature of the system we could capture the dynamical response of the system from a fluid-fluid to bridging induced network states The structural properties when analyzed show a strongly networked solid-like transition which has been augmented using dynamical analysis. Calculations show the slowing down of nanoparticle diffusion in the network phase due tomore » jamming of the nanoparticles. At certain parameter range, the equilibrium stress-stress autocorrelation function does not decay confirming the existence of solid-like behavior. The change in mechanical properties is supported by the morphological observations.« less
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