Data evaluation in light scattering from solutions of branched polyethylene

The molecular dimensions of branched polyethylene published in the literatu re were re-evaluated to obtain the radii of gyration R-G and other relevant topological parameters. By means of the exponent a(S) in the relationships R-G = b . M-s(a) the reliability of the data and reasons for deviations we re discussed. Linear and branched polyethylenes are molecularly dissolved o nly in the good solvent, tetralin, whereas in 1-chloronaphthalene and 1,2,4 -trichlorobenzene the exponent a(S) is lower than expected for good solvent s. Microgels and aggregates affect the exponents. After correction of the d ata by a two component separation method in combination with model calculat ions and the analysis of scattering curves, a consistent picture is obtaine d. This procedure is demontrated with fractions of branched polyethylene in the theta solvent diphenylmethane, which are indicating incomplete molecul ar dissolution.