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

Abstract

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
Volume135
Issue number15
DOIs
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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