title: Chirality-dependent friction of bulk molecular solids.
abstract: We show that the solid-solid friction between bulk chiral molecular solids can depend on the relative chirality of the two materials. In menthol and 1-phenyl-1-butanol, heterochiral friction is smaller than homochiral friction, while in ibuprofen, heterochiral friction is larger. Chiral asymmetries in the coefficient of sliding friction vary with temperature and can be as large as 30%. In the three compounds tested, the sign of the difference between heterochiral and homochiral friction correlated with the sign of the difference in melting point between racemate (compound or conglomerate) and pure enantiomer. Menthol and ibuprofen each form a stable racemic compound, while 1-phenyl-1-butanol forms a racemic conglomerate. Thus, a difference between heterochiral and homochiral friction does not require the formation of a stable interfacial racemic compound. Measurements of chirality-dependent friction provide a unique means to distinguish the role of short-range intermolecular forces from all other sources of dissipation in the friction of bulk molecular solids.
authors.affiliation: School of Engineering and Applied Sciences and ‡Departments of Chemistry and Chemical Biology and of Physics, Harvard University , Cambridge, Massachusetts 02138, United States.
authors.forename: Dian
authors.initials: D
authors.lastname: Yang
authors.forename: Adam E
authors.initials: AE
authors.lastname: Cohen
mesh_terms: D017276:Friction; D007052:Ibuprofen / Q000737:chemistry; D008610:Menthol / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D008610:Menthol; D007052:Ibuprofen