Characterization of low-density polyethylene by gel permeation chromatography—III. Study on the Drott method using a whole polymer

Two features of the Drott iterative procedure for the estimation of long-chain branching have been examined, viz. the proportionality between the number of long-chain branches n per molecule and its molecular weight M, and the exponent ? relating the ratio of intrinsic viscosities of branched and linear polymers of the same weight-average molecular weight to n. The original Drott model describing the distribution of long-chain branches (LCB) has been replaced by a more general equation: n = const. M^B and an examination of the effect of the exponents B and ? on the molecular weight distribution (MWD) and LCB characteristics carried out. The analysis has revealed that, unless information on the LCB distribution is available, the method described by Drott for which B = 1 can hardly give meaningful information on MWD and LCB for commercial low-density polyethylenes.