Effect of reactive end groups on the rheology of disk lubricant systems

We systematically investigate the properties of perfluoropolyethers with different weights and chain-end functionalities, which are used as lubricants in hard disk drive systems. The temperature dependence of the viscosity yields an Arrhenius form; the activation energy and hydrodynamic volume are determined for different molecular weights. The activation energy depends on both end group functionality and molecular weight. Also, modified Cole-Cole plots for storage modulus vs. loss modulus reveal the presence of microstructures due to the interaction of polymer chain-end groups in the bulk. The viscosity-molecular weight relationship exhibits a remarkable crossover behaviour at a critical molecular weight (M_c ) for ZdolTX (Zdol with C/O end group ratio of 1.7). Fly stiction (tribology) data also exhibit an M_c and an excellent correlation with viscosity (rheology) is obtained