Viscoelasticity and solution viscosity of perfluoropolyether lubricants

Viscoelastic characteristics including the viscosity, storage modulus, and loss modulus of perfluoropolyether (PFPE) lubricants with reactive endgroups are examined via a rotational rheometer. Both temperature and molecular weight effects on rheological properties are extensively analyzed via the Rouse theory in polymer dynamics. The modified Cole-Cole plots for storage modulus vs. loss modulus exhibits the presence of microstructures due to the interaction among PFPE endgroups. To examine the solvent effect during the dip-coating process, we examined the intrinsic viscosity, or Huggins coefficient for dilute PFPE solutions, which depends on the aspect ratio of PFPE cluster and potential energy among PFPE molecules. We also correlated the viscoelastic data with the tribological data.