Chaotrope vs. kosmotrope: Which one has lower friction

Yi He, Qing Shao, Shengfu Chen, Shaoyi Jiang

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


We examine the frictional properties of zwitterionic surfaces and explore whether chaotropic or kosmotropic charged groups are preferred to achieve lower friction. Self-assembled monolayers of carboxybetaine (CB-SAMs) and sulfurbetaine (SB-SAMs) are used as model surfaces as they contain the same positively charged group, but different negatively charged ones. The negatively charged groups are kosmotropic carboxylates in the CB-SAM surfaces and chaotropic sulfonate groups in the SB-SAM surfaces, respectively. The results show that the friction of the SB-SAM surfaces is even lower than that of the CB-SAM surfaces although both surfaces have low friction. This suggests that chaotropic charged groups are better in reducing friction than kosmotropic groups. The lower friction of the SB-SAM surfaces over the CB-SAM can be explained by the higher mobility of water near the SB-SAM surfaces, as shown in the survival autocorrelation function and the dipole autocorrelation function of hydration water molecules.

Original languageEnglish
Article number154702
JournalJournal of Chemical Physics
Issue number15
StatePublished - Oct 21 2011

Bibliographical note

Funding Information:
We would like to thank the National Science Foundation (CMMI 0758358) and the American Chemical Society, Petroleum Research Funds (ACS PRF #48096-AC7) for financial support.

ASJC Scopus subject areas

  • General Physics and Astronomy
  • Physical and Theoretical Chemistry


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