@article{Cai2022, 
author = {Wanhao Cai and Duo Xu and Fa Zhang and Junhao Wei and Song Lu and Linmao Qian and Zhongyuan Lu and Shuxun Cui},
title = {Intramolecular hydrogen bonds in a single macromolecule: Strength in high vacuum versus liquid environments},
year = {2022},
journal = {Nano Research},
volume = {15},
number = {2},
pages = {1517-1523},
keywords = {atomic force microscopy, vacuum, single-molecule studies, simulations, hydrogen bond, polymer elasticity},
url = {https://www.sciopen.com/article/10.1007/s12274-021-3696-1},
doi = {10.1007/s12274-021-3696-1},
abstract = {As a weak non-covalent interaction, hydrogen bond (H-bond) is highly susceptible to the environmental interference. However, the direct quantification of a single H-bond under an interference-free condition is still a challenge. Herein, the intramolecular H-bond in a model system, poly(N-isopropylacrylamide), is studied in high vacuum by single-molecule atomic force microscopy and steered molecular dynamics simulations, which allows the precise quantification of H-bond strength in an interference-free state. Control experiments show that the H-bond is significantly weakened in nonpolar solvent, even if the dielectric constant is very close to vacuum. If a polar solvent is used as the environment, the H-bond will be further weaker or even broken. These results imply that for experiments in any liquid environment, the H-bond strength (ΔG) will be only ~ 50% or even less of that measured in vacuum. Further analysis shows that in liquid environments, ΔG decays in a quasi-linear way with the increase of the dielectric constant (ε). For H-bond studies in future, the result measured in vacuum can be set as the standard value, namely, the inherent strength. This approach will provide fundamental insights into the H-bond participated nano-structures and materials in different environments.}
}