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Natural rubber-SiO 2 nanohybrids: Interface structures and dynamics
Published in Royal Society of Chemistry
2019
PMID: 30816894
Volume: 15
   
Issue: 13
Pages: 2826 - 2837
Abstract
Homogeneous dispersion of silica nanoparticles (SiO 2 NPs) in natural rubber (NR) is a key challenge for engineering high-performance nanocomposites and elucidation of their structure on a molecular basis. Towards this, the present work devised a novel route for obtaining 3D self-assembled SiO 2 NP-NR nanocomposites under aqueous conditions and in the presence of Mg 2+ , by establishing a molecular bridge that clamped the negatively charged NR and SiO 2 colloidal particles with a favoured NR-SiO 2 NP hetero-aggregation. The characteristic NR-SiO 2 NP hetero-aggregates displayed a decreased heat capacity with increase in the SiO 2 mass-fraction, implying a restricted NR chain mobility. Such changes in the interfacial layers were tapped by 29 Si NMR, DFT calculations and molecular dynamics simulations towards a mechanistic understanding of the structure and dynamics of the NR/SiO 2 NP hybrid. Simple models were used to illustrate basic ideas; specific electrostatic interactions such as ion-dipole and H-bonding interactions proved to be the driving forces for the organized assembly leading to the NR-SiO 2 hetero-aggregate over the NR-NR or SiO 2 NP-SiO 2 NP homo-aggregate. Molecular dynamics simulation of the aqueous canonical ensemble of the hybrid showed the stable molecular conformation to reveal a SiO 2 NP spherical core encapsulated by a hydrophobically interconnected NR polymer layer as the outer shell, as a unique structural model. Specifically, the lipid end of the NR was involved electrostatically while the lysine end (the protein part of NR) H-bonded to the core silica cluster thereby restricting random aggregation. The calculated negative free energy changes for the hetero-aggregate composites via their vibrational and rotational spectra proved the spontaneity of composite formation. © 2019 The Royal Society of Chemistry.
About the journal
JournalData powered by TypesetSoft Matter
PublisherData powered by TypesetRoyal Society of Chemistry
ISSN1744683X
Open AccessNo
Concepts (20)
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    Agglomeration
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    Aggregates
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    Amino acids
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    Free energy
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    Hydrogen bonds
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    Molecular dynamics
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    Nanocomposites
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    RUBBER
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    Silica
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    Silica nanoparticles
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    Specific heat
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    Composite formation
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    H-BONDING INTERACTION
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    HOMOGENEOUS DISPERSIONS
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    INTERFACE STRUCTURES
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    Molecular conformation
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    Molecular dynamics simulations
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    STRUCTURAL MODELING
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    Structure and dynamics
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    Sio2 nanoparticles