摘要
90°is the limitation oflyophilicity and lyophobicity for ideal surface for centuries,but it has been proved to be contradictory on some occasions.The symmetrical surfaces with different surface tensions can attract or repel each other in water.Therefore,at the molecular level,the Iyophilicity or lyophobicity is the results of interactions between the liquids and substrates.Here,using atomic force microscope(AFM)to measure interaction forces between symmetrical self-assembled monolayers(SAMs)in different liquids,we found that the SAMs repel each other when the surfaces are hydrophilic whereas attract when hydrophobic in water.The contact angle corresponding to the transition of attraction to repulsion is approximate to 65°,defined as the intrinsic wetting threshold(IWT)of water.For ethylene glycol(EG),dimethyl sulfoxide(DMSO),N,N-dimethyl formamide(DMF),the IWTs could be determined by changes of adhesion forces between SAMs.This research redefined the IWTs for liquids,which is the essential guide to both basic theory and applications of wettability.
基金
This research is supported by the National Natural Science Foundation of China(Nos.21972154,21988102,and 22090052)
Frontier Science Key Projects of CAS(ZDBS-LY-SLH022)
the National Research Fund of China for Fundamental Key Projects(No.2019YFA0708700)
Project funded by China Postdoctoral Science Foundation(No.2020M670091).