Natural rubber-SiO₂ nanohybrids: interface structures and dynamics

Area of Science:

• Materials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Achieving homogeneous dispersion of silica nanoparticles (SiO2 NPs) in natural rubber (NR) is crucial for developing advanced nanocomposites.
• Understanding the molecular structure of these nanocomposites is essential for optimizing their performance.

Purpose of the Study:

• To develop a novel aqueous-based method for creating 3D self-assembled SiO2 NP-NR nanocomposites.
• To elucidate the molecular mechanisms driving the hetero-aggregation of NR and SiO2 NPs.
• To characterize the structure and dynamics of the resulting NR/SiO2 NP hybrid.

Main Methods:

• Utilized Mg2+ to establish a molecular bridge for NR-SiO2 NP hetero-aggregation in aqueous conditions.
• Employed 29Si NMR, Density Functional Theory (DFT) calculations, and molecular dynamics (MD) simulations.
• Analyzed heat capacity changes and interfacial layer dynamics.

Main Results:

• A novel route for 3D self-assembled SiO2 NP-NR nanocomposites was successfully developed under aqueous conditions.
• Hetero-aggregation was driven by electrostatic interactions (ion-dipole and H-bonding) between NR and SiO2 NPs.
• MD simulations revealed a stable core-shell structure: a SiO2 NP core encapsulated by a NR polymer layer.

Conclusions:

• The study presents a unique structural model for NR/SiO2 NP hybrids with a SiO2 core and NR shell.
• Specific electrostatic interactions at the NR lipid and lysine ends with silica dictate the self-assembly process.
• Negative free energy changes confirm the spontaneous formation of these hetero-aggregate composites.