We report direct measurements of interaction forces between hydrophobic molecules in water measured by force spectroscopy.  Molecules understudy are tethered by flexible hydrophilic poly (ethylene glycol) linkers to the probes of atomic force microscope (AFM) and to the solid substrates removing the spurious surface effects.  Intermolecular �hydrophobic� bonds between alkane molecules are formed and ruptured during the approach-withdraw motion of the probe.  The data analysis focuses on the distribution of rupture forces measured at different pulling rates.  Measurements of rupture forces between hexadecane molecules attached at different points suggest a conformational transition of individual molecules from extended to collapsed states during dimerization.  Furthermore, the shapes of the distributions of rupture forces for linear alkanes attached by their ends differ considerably from predictions of simple kinetic theories.  Deviation at the high-force side of the distribution is attributed to the contributions of multiple bond ruptures.  The remaining deviation can be explained by suggesting that alkanes are separated from different dimeric states.

Experimental measurements of hydrophobic interactions at a single-molecule level by force spectroscopy

243rd National Meeting (2012)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.