EFFECT OF DEFORMATION ON THE SURFACE-COMPOSITION OF MULTICOMPONENT POLYMERS - II - BLENDS OF POLYDIMETHYLSILOXANE-POLYSULFONE BLOCK-COPOLYMERS IN POLYCHLOROPRENE

The effect of uniaxial stretching on the surface composition of dilute blends of polydimethylsiloxane/polysulfone 2500/44,000 and 2500/3500 block copolymers in polychloroprene is studied using X-ray photoelectr on spectroscopy. The surface of the initial (unstretched) blends is fo und to be covered by a discontinuous copolymer overlayer with a thickn ess greater than the XPS sampling depth. The stretching leads to a sub stantial drop in the extent of the copolymer surface segregation. For the 2500/ 3500 block copolymer, the dependence of the surface composit ion of the blends on the stretching degree is well described by a homo geneous deformation model, whereas for blends of the 2500/44,000 copol ymer, the stretching of the copolymer overlayer lags noticeably behind that of the polychloroprene matrix. In the blends of the 2500/3500 co polymer, the stretching has practically no effect on the distribution of the copolymer components in the near-surface region. By contrast, t he 2500/44,000 copolymer shows a substantial surface depletion of silo xane with stretching. (C) 1998 John Wiley & Sons.