Intramolecular hydrogen bonds in a single macromolecule:Strength in high vacuum versus liquid environments  

作　　者：Wanhao Cai Duo Xu Fa Zhang Junhao Wei Song Lu Linmao Qian Zhongyuan Lu Shuxun Cui 

机构地区：[1]Key Laboratory of Advanced Technologies of Materials(Ministry of Education),Southwest Jiaotong University,Chengdu 610031,China [2]State Key Laboratory of Supramolecular Structure and Materials,Institute of Theoretical Chemistry,Jilin University,Changchun 130023,China

出　　处：《Nano Research》2022年第2期1517-1523,共7页纳米研究（英文版）

基　　金：supported by the National Natural Science Foundation of China(No.21774102).

摘　　要：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(△G)will be only -50% or even less of that measured in vacuum.Further analysis shows that in liquid environments,AG 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.

关 键 词：hydrogen bond single-molecule studies atomic force microscopy VACUUM polymer elasticity simulations 

分 类 号：O6[理学—化学]