CHAIN CONFORMATION IN SHEARED POLYMER MELTS AS REVEALED BY SANS

The conformation of polymer chains in the melt during simple shear flo w has been characterized by SANS on a narrow molecular weight distribu tion polystyrene sample. An apparatus has been designed which allows o ne to freeze-in by quenching uniform shear orientations in thick speci mens on which the scattering experiments can be performed in the three principal shear directions. In the 1-2 shearing plane, the orientatio n of molecular anisotropy with respect to the shear axes is found to d epend on the magnitude of the scattering vector and therefore on the c onsidered length scale on the chain. A method has been proposed to ana lyze the data in this plane. The chain dimension in the neutral shear direction remains unaffected by the flow. The birefringence and extinc tion angle have been measured and compared to the SANS data. Finally, the respective influence of shear stress and shear strain on the chain conformation is discussed.