SMALL-ANGLE NEUTRON-SCATTERING INVESTIGATIONS OF MELT MISCIBILITY ANDPHASE SEGREGATION IN BLENDS OF LINEAR AND BRANCHED POLYETHYLENES AS AFUNCTION OF THE BRANCH CONTENT

We have performed a series of small angle neutron scattering (SANS) ex periments on blends of linear and branched polyethylenes to investigat e the level of branching that is required to phase separate the system . These results confirm that the mixtures are homogenous for all compo sitions when the branch content is low (i.e., <4 branches/100 backbone carbon atoms for molecular weight M(w) similar to 10(5)). However, wh en the branch content is higher (typically greater than or equal to 8 branches/100 backbone carbons), the blends phase separate. Segregation can also be driven by isotope effects, when the molecular weight is s ufficiently high so that the product of the polymerization index and t he H-1/D-2 interaction parameter (N chi(HD)) > 2. In each case, the re solution of conventional SANS pinhole cameras (Q(main) similar to 10(- 3) Angstrom(-1)) is adequate to determine the state of mixing, even fo r systems with large domains.