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Tunable Encapsulation Structure of Block Copolymer Coated Single-Walled Carbon Nanotubes in Aqueous Solution

by Y Han, S Ahn, G S Smith, C Do

Abstract 

A molecular building block of single-walled carbon nanotubes (SWNT) was fabricated and investigated by small-angle neutron scattering using the neutron scattering contrast difference among the SWNTs, polymers, and solvent (D2O). Fabrication of nano-sized smart-building blocks is crucial for development of advanced functional materials. This research shows an efficient and simple way to fabricate and manipulate carbon-based nano building blocks in aqueous systems whose encapsulation layer is tunable via temperature. Such a system can be used to provide thermal or electrical conductivity to a material.  (hi-res image)
Nanosized and shape-tunable molecular building blocks can provide great opportunities for the fabrication of precisely controlled nanostructures. In this work, we have fabricated a molecular building block of single-walled carbon nanotubes (SWNTs) coated by PPO–PEO–PPO block copolymers whose encapsulation structure can be controlled via temperature or addition of small molecules. The structure and optical properties of SWNT block copolymers have been investigated by small-angle neutron scattering (SANS), ultraviolet–visible (UV–vis) spectroscopy, atomic force microscopy (AFM), and molecular dynamics (MD) simulation. The structure of the hydrated block copolymer layer surrounding SWNT can be controlled reversibly by varying temperature as well as by irreversibly adding 5-methylsalicylic acid (5MS). Increasing hydrophobicity of the polymers with temperature and strong tendency of 5MS to interact with both block copolymers and π orbitals of the SWNTs are likely to be responsible for the significant structural change of the block copolymer encapsulation layer, from loose corona shell to tightly encapsulating compact shell. Our result shows an efficient and simple way to fabricate and manipulate carbon-based nano building blocks in aqueous systems with tunable structure.

 

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Publication Citation

Macromolecules 2015 48 (11) pp 3475-3480
DOI: 10.1021/acs.macromol.5b00456

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