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Title: Controlling Interfacial Dynamics: Covalent Bonding versus Physical Adsorption in Polymer Nanocomposites

Abstract

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 low 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 ismore » 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

Authors:
 [1];  [2];  [2];  [2];  [2];  [2];  [3];  [4];  [4];  [5];  [5];  [5];  [6];  [4];  [7];  [7]
  1. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Physics and Astronomy
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS)
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science (CNMS); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Computer Science and Mathematics Division
  5. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry
  6. Columbus State Univ., Columbus, GA (United States). Dept. of Chemistry
  7. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division; Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry
Publication Date:
Research Org.:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1302936
Grant/Contract Number:
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
ACS Nano
Additional Journal Information:
Journal Volume: 10; Journal Issue: 7; Journal ID: ISSN 1936-0851
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 77 NANOSCIENCE AND NANOTECHNOLOGY; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; glass transition; interfacial dynamics; polymer nanocomposites; polymer-grafted nanoparticles; segmental dynamics; self-consistent field theory

Citation Formats

Holt, Adam P., Bocharova, Vera, Cheng, Shiwang, Kisliuk, Alexander M., White, B. Tyler, Saito, Tomonori, Uhrig, David, Mahalik, J. P., Kumar, Rajeev, Imel, Adam E., Etampawala, Thusitha, Martin, Halie, Sikes, Nicole, Sumpter, Bobby G., Dadmun, Mark D., and Sokolov, Alexei P.. Controlling Interfacial Dynamics: Covalent Bonding versus Physical Adsorption in Polymer Nanocomposites. United States: N. p., 2016. Web. doi:10.1021/acsnano.6b02501.
Holt, Adam P., Bocharova, Vera, Cheng, Shiwang, Kisliuk, Alexander M., White, B. Tyler, Saito, Tomonori, Uhrig, David, Mahalik, J. P., Kumar, Rajeev, Imel, Adam E., Etampawala, Thusitha, Martin, Halie, Sikes, Nicole, Sumpter, Bobby G., Dadmun, Mark D., & Sokolov, Alexei P.. Controlling Interfacial Dynamics: Covalent Bonding versus Physical Adsorption in Polymer Nanocomposites. United States. doi:10.1021/acsnano.6b02501.
Holt, Adam P., Bocharova, Vera, Cheng, Shiwang, Kisliuk, Alexander M., White, B. Tyler, Saito, Tomonori, Uhrig, David, Mahalik, J. P., Kumar, Rajeev, Imel, Adam E., Etampawala, Thusitha, Martin, Halie, Sikes, Nicole, Sumpter, Bobby G., Dadmun, Mark D., and Sokolov, Alexei P.. 2016. "Controlling Interfacial Dynamics: Covalent Bonding versus Physical Adsorption in Polymer Nanocomposites". United States. doi:10.1021/acsnano.6b02501. https://www.osti.gov/servlets/purl/1302936.
@article{osti_1302936,
title = {Controlling Interfacial Dynamics: Covalent Bonding versus Physical Adsorption in Polymer Nanocomposites},
author = {Holt, Adam P. and Bocharova, Vera and Cheng, Shiwang and Kisliuk, Alexander M. and White, B. Tyler and Saito, Tomonori and Uhrig, David and Mahalik, J. P. and Kumar, Rajeev and Imel, Adam E. and Etampawala, Thusitha and Martin, Halie and Sikes, Nicole and Sumpter, Bobby G. and Dadmun, Mark D. and Sokolov, Alexei P.},
abstractNote = {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 low 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.},
doi = {10.1021/acsnano.6b02501},
journal = {ACS Nano},
number = 7,
volume = 10,
place = {United States},
year = 2016,
month = 6
}

Journal Article:
Free Publicly Available Full Text
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Cited by: 12works
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  • Polymer nanocomposites (PNCs) are materials based on a class of filled plastics that contain relatively small amounts of nanoparticles, which can impart improved structural, mechanical, and thermal properties relative to the neat polymer. However, the homogeneous dispersion of the nanoparticles into a polymer matrix is critical and an impeding factor for the controlled enhancement of PNC properties. In this work, we provide new insight into the importance of polymer chain connectivity and nanoparticle shape and curvature on the formation of noncovalent electron donoracceptor (EDA) interactions between polymers and nanoparticles. This is accomplished by experimentally monitoring the dispersion of nanoparticles inmore » copolymers containing varying amounts of functional moieties that can form noncovalent interactions with carbon nanoparticles with corroboration through density functional calculations. The results show that the presence of a minority of interacting functional groups within a polymer chain leads to an optimum interaction between the polymer and fullerene. Density functional theory calculations that identify the binding energy and geometry of the interaction between the functional monomers and fullerenes correspond very well with the experimental results. Moreover, comparison of these results to similar studies with single-walled carbon nanotubes (SWNT) indicate a distinct difference in the ability of EDA interactions to improve the dispersion of fullerenes relative to their impact on SWNT. Thus, the polymer chain connectivity, the polymer chain conformation, and size and shape of the nanoparticle modulate the formation of intermolecular interactions and directly impact the dispersion of the resultant nanocomposite.« less
  • Polymer nanocomposites (PNCs) are materials based on a class of filled plastics that contain relatively small amounts of nanoparticles, which can impart improved structural, mechanical, and thermal properties relative to the neat polymer. However, the homogeneous dispersion of the nanoparticles into a polymer matrix is critical and an impeding factor for the controlled enhancement of PNC properties. In this work, we provide new insight into the importance of polymer chain connectivity and nanoparticle shape and curvature on the formation of noncovalent electron donor-acceptor (EDA) interactions between polymers and nanoparticles. This is accomplished by experimentally monitoring the dispersion of nanoparticles inmore » copolymers containing varying amounts of functional moieties that can form noncovalent interactions with carbon nanoparticles with corroboration through density functional calculations. The results show that the presence of a minority of interacting functional groups within a polymer chain leads to an optimum interaction between the polymer and fullerene. Density functional theory calculations that identify the binding energy and geometry of the interaction between the functional monomers and fullerenes correspond very well with the experimental results. Moreover, comparison of these results to similar studies with single-walled carbon nanotubes (SWNT) indicate a distinct difference in the ability of EDA interactions to improve the dispersion of fullerenes relative to their impact on SWNT. Thus, the polymer chain connectivity, the polymer chain conformation, and size and shape of the nanoparticle modulate the formation of intermolecular interactions and directly impact the dispersion of the resultant nanocomposite.« less
  • 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 variousmore » 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.« less