Hydrogen Bonding in Disk Lubricants

A TOP (touch-down-pressure) study revealed, for disks coated with Z-tetraol but not for disks coated with Z-dol, an anomalous growth of droplets of several nanometers across atop the disk surface in a high humidity environment. Hydrogen bonding interaction amongst water molecules and end-groups of Z-dol and Z-tetraol, and the effect of alkali-halide upon such interaction were examined by a quantum mechanical molecular dynamics method. It is revealed: (1) an ionic contaminant such as alkali-halide is a strong attractant of water molecules, (2) Z-tetraol end groups, if present, would readily encapsulate the resulting brine droplets, and (3) no corresponding interfacial reaction occurs between Z-dol end and brine solution. The anomalous TDP result observed with Z-tetraol disks is attributed to the growth and presence of brine droplets so stabilized by lubricant encapsulation