AMBIGUITIES IN THE INTERPRETATION OF SMALL-ANGLE NEUTRON-SCATTERING FROM BLENDS OF LINEAR AND BRANCHED POLYETHYLENE - COMMENTS

Small-angle neutron scattering has recently been applied to study liqu id-liquid phase separation in blends of branched and linear polyethyle nes. While experimental results from two groups are basically the same , interpretations differ strongly. The analyses of Schipp et al. (Poly mer, 1996, 37, 2291), which favour phase separation, are shown to be i ncorrect. There is no contraction of chain dimensions in blends of lin ear and branched polyethylene chains. The postulate that large domain sizes in two-phase blends obscure the presence of phase separation is correct in principle, but requires dimensions some ten times larger th an the similar to 1 mu m sizes reported for the systems in question. T hus, neutron scattering does not support liquid-liquid phase separatio n inferred from indirect studies of polyethylene blends. (C) 1997 Else vier Science Ltd.