Bestimmung der langkettenverzweigung von hochdruckpolyäthylen durch streulicht- und viskositätsmessungen

Linear and branched polyethylene were fractionated by solvent gradient chromatography. The fractions were characterized by light scattering and viscosity measurements. The relationship between the molecular weight and the limiting viscosity number and that between the molecular weight and the radius of gyration in α-chloronaphthaline at 127°C were determined. The exponent of the equation between the ratio 〈g_η〉Θ of the limiting viscosity numbers of branched and linear fractions of the same molecular weight M_w and the corresponding ratio 〈g_η〉_Θ,w of the radii of gyration for Θ-conditions was By this equation, the long chain branching of high pressure polyethylene can be determined from 〈g_η〉, the ratio of the limiting viscosity numbers in thermodynamically good solvents, which is within the experimental limits of error identical to 〈g_η〉_Θ in a Θ-solvent. Almost independent of the molecular weight, for the branched polyethylene fractions 1,4 long chain branching points per 1000 C-atoms were obtained.