Theory

How to Measure Branching in Polymer by SEC/GPC

Branching analysis is complex and requires some basic shape and structural information of the macromolecule of interest. It is obtained relative to a linear reference. In order to provide comprehensive analysis for the complete range of molecular weight distribution, intrinsic viscosity data is used as a tool for measuring branching. At a given molecular weight, the branched molecule possesses smaller hydrodynamic volume (i.e. higher molecular density) and therefore lower intrinsic viscosity compared to its linear counterpart.

Branching Ratio is defined as the ratio of intrinsic viscosity values of the branched and the linear samples; ranging from 0 to 1. Values close to 1 indicate little or no branching while values close to 0 suggest large conformation change and therefore significant branching.

Using common Zimm-Stockmayer equations and methods, Number of Branches, Branching Frequency and Branching per Molecule parameters can be calculated across the distribution.

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