NANORHEOLOGY OF ADSORBED DIBLOCK COPOLYMER LAYERS

We investigate the mechanical properties of ultra-thin layers of polys tyrene/poly (2-vinylpyridine) (PS/P2VP) block copolymers by means of a Surface Forces Apparatus adapted to operate asa rheometer at the mole cular level. Two systems are studied: ''brush/wall'' and ''brush/brush ''. A comparison of the normal force curves shows that when brushes ar e compressed against each other, they contract rather than interpenetr ate. Nanorheological experiments have been carried out on both systems but reliable measurements have been obtained only on the brush/wall s ystem. The complex shear modulus, characterizing the confined medium, has been measured as a function of separation. Its distance dependence is compared with a scaling model describing the linear shear behaviou r of a brush confined by a neutral surface.