RHEOLOGY OF OLEFINIC COPOLYMER LAYERS ADSORBED ON SOLID-SURFACES

The rheology of two adsorbed layers of olefinic copolymers (OCPs) betw een two cobalt surfaces was investigated using a surface force apparat us (SFA). Each polymer layer is obtained by adsorption in a dilute sol ution of OCP and dispersant OCP (DOCP) in a 175 neutral solvent basest ock at 24 degrees C. The aim of these experiments is the mechanical ch aracterization of the compressed polymer films. The hydrodynamic thick ness L(H) detected is compared with the thickness of the polymer layer s L and the hydrodynamic radius R(H) of the polymer coil in solution. All these distances, strongly related to the chemical structure of the polymer, indicate that the layers are not always homogeneous. For OCP , 0.55L approximate to L(H) approximate to 2R(H), and for DOCP L appro ximate to L(H) approximate to 2.7R(H). Finally the two layers present different inelastic behaviors. The DOCP layer presents a mesh more com pact and more uniform than the OCP layer as indicated by the thickness measurements.