A method for characterization of long-chain branched polymers by GPC and intrinsic viscosity

The authors previously reported a method for molecular weight and long-chain branching distributions using GPC and intrinsic viscosity measurements on whole polymer and fractions [1]. The method does not require prior knowledge of the functional relationship between branching frequency and molecular weight. Applications included “randomly” branched polymers, prepared by free radical initiation, and anionically polymerized macromolecules branched by various techniques leading to specific distributions of branches. Additional examples are given in the present report. The technique has been applied both without and with GPC band spreading correction. The effect of this correction on the resulting estimate of the long-chain branching distribution is insignificant. When the method is applied to whole polymer only (without preparative fractionation), an average branching factor is obtained, which serves as a useful partial characterization of long-chain branching. Use of this alternative is discussed and illustrated with examples of low and high density polyethylene, branched styrene-butadiene block copolymers, star-branched polybutadiene and others. For the special case of statistically random branching, the average branching factor may be converted to a branching frequency by a straightforward computer program, leading to a description of branching similar to that of Drott and Mendelson [2].