Boundary Lubricant Film Properties of Z-Tetraol Modified by Benzene Rings

The adsorbed film structures of perfluoropolyethers (PFPEs) modified with benzene functional group(s)
either on the chain ends or in the middle of the main chain are investigated. Surface energy as a function of
PFPE film thickness and of time shows the benzene functional group orients towards the carbon surface
(CNx). The re-orientation is kinetically much slower than for hydroxyl end groups for PFPEs having
similar main chain compositions. The bonding of the benzene functional group to the underlying CNx
surface is significantly weaker than OH functional groups and/or more readily removed by the solvent used
to originally deposit the PFPE film onto the carbon surface. Model dimer interactions via ab initio
computational chemistry calculations shows a significantly longer closest contact distance for the
benzene/CNx dimer compared to OH/CNx dimer, indicative of the weaker intermolecular interaction.