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

We systematically investigate the rheological properties of perfluoropolyet hers with different molecular weights and chain-end functionalities, which are used as lubricants in hard disk drive systems. The temperature dependen ce of the viscosity yields an Arrhenius form; the activation energy and hyd rodynamic volume are determined for different molecular weights. The activa tion energy depends on both end group functionality and molecular weight. A lso, modified Cole-Cole plots for storage modulus vs. loss modulus reveal t he presence of microstructures due to the interaction of polymer chain-end groups in the bulk. The viscosity-molecular weight relationship exhibits a remarkable crossover behavior at a critical molecular weight (M-c) for Zdol TX (Zdol with C/O end group ratio of 1.7), Fly stiction (tribology) data al so exhibit an M-c, and an excellent correlation with viscosity (rheology) i s obtained.