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Issue 41, 2016
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Effect of the size of solvent molecules on the single-chain mechanics of poly(ethylene glycol): implications on a novel design of a molecular motor

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Abstract

Excluded-volume (EV) interaction, also known as the EV effect, can drive the collapse of polymer chains in a polymer solution and promote the crystallization of polymer chains. Herein we report, for the first time, the effect of EV interaction on the single-chain mechanics of a polymer, poly(ethylene glycol) (PEG). By using AFM-based single-molecule force spectroscopy, the single-chain mechanics of a PEG chain has been detected in various nonpolar organic solvents with different molecule sizes. It is observed that the nonpolar solvents can be classified into two categories. In the small-sized organic solvents (e.g., tetrachloroethane and n-nonane), PEG presents its inherent elasticity, which is consistent with the theoretical single-chain elasticity from quantum mechanical calculations. However, in the middle-sized solvents (e.g., n-dodecane and n-hexadecane), the single-chain entropic elasticity of PEG is influenced by EV interactions noticeably, which indicates that the PEG chain tends to adopt a compact conformation under these conditions. To stretch a PEG chain from a free state to a fully extended state, more energy (1.54 kBT per repeating unit) is needed in small-sized organic solvents than in middle-sized organic solvents. It is expected that a partially stretched PEG chain would shrink to some extent when the solvent is changed from a middle-sized organic solvent to a small-sized one. Accordingly, a novel design of a PEG-based single-molecule motor that works with solvent stimuli is proposed.

Graphical abstract: Effect of the size of solvent molecules on the single-chain mechanics of poly(ethylene glycol): implications on a novel design of a molecular motor

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Publication details

The article was received on 25 Jul 2016, accepted on 19 Sep 2016, published on 19 Sep 2016 and first published online on 19 Sep 2016


Article type: Paper
DOI: 10.1039/C6NR05863A
Citation: Nanoscale, 2016,8, 17820-17827
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    Effect of the size of solvent molecules on the single-chain mechanics of poly(ethylene glycol): implications on a novel design of a molecular motor

    Z. Luo, B. Zhang, H. Qian, Z. Lu and S. Cui, Nanoscale, 2016, 8, 17820
    DOI: 10.1039/C6NR05863A

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