la7b01921_si_001.pdf (1.2 MB)
Effect of the Chain Length and Temperature on the Adhesive Properties of Alkanethiol Self-Assembled Monolayers
journal contribution
posted on 2017-10-01, 00:00 authored by Hubert Gojzewski, Michael Kappl, Arkadiusz PtakStable
and hydrophobic self-assembled monolayers of alkanethiols
are promising materials for use as lubricants in microdevices and
nanodevices. We applied high-rate dynamic force spectroscopy measurements
to study in detail the influence of the chain length and temperature
on the adhesion between methyl-terminated thiol monolayers and a silicon
nitride tip. We used the Johnson–Kendall–Roberts model
to calculate the number of molecules in adhesive contact and then
the Dudko–Hummer–Szabo model to extract the information
about the position and the height of the activation barrier per single
molecule. Both parameters were determined and analyzed in the temperature
range from 25 to 65 °C for three thiols: 1-decanethiol (measured
previously), 1-tetradecanethiol, and 1-hexadecanethiol. We associate
the increase of the activation barrier parameters versus the chain
length with lower stiffness of longer molecules and higher effectiveness
of adhesive bond formation. However, we relate the thermal changes
of the parameters rather to rearrangements of molecules than to the
direct influence of temperature on the adhesive bonds.