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Tetra Detector Array
A revolutionary, integrated multiple-detector device designed for the characterization of natural and synthetic polymers and copolymers, proteins, protein conjugates, excipients and other macromolecules. Comprised of modular Refractive Index, Ultra-Violet, Low Angle Light Scattering and Viscometer detectors.
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Complete DSV Systems
For Dilute Solution Viscosity, Viscotek takes pride in being the only manufacturer capable of supplying you with a comprehensive system solution, regardless of your viscosity testing requirements.
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"The service provided by Viscotek representatives is unmatched by any other in the industry... A wonderful addition to the polymer community."
- E.F, Ph.D., Academic Institution
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"The GPCmax and Triple Detector System is state-of-the-art while remaining affordable and easy to use."
- M. G., Ph.D., Academic Institution |
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GPC Theory: Polymer Branching |
As we have seen in Polymer Structure, the Viscometer can uncover valuable information about the structure of a polymer and can help determine at what point changes in branching occur. This section describes the theory behind the quantification of branching theory
behind the quantification of polymer branching, so that as well as determining when a polymer is branched, we can determine how much branching occurs.
The image below illustrates the difference in pervaded volume between a linear chain
and a branched chain with the same total chain length. Since the hydrodynamic volume
is smaller with the same mass enclosed, the density must be higher, producing a
lower Intrinsic Viscosity.
Zimm and Stockmayer formulated several equations to quantify the number of branches in a polymer based on how it compares to a linear (non-branched) variant of the same polymer. The 3 most common Zimm-Stockmayer equations for polymer branching are:
In each of these equations, the number of braches (BMor ňw) is related to an entity gM. In turn,
g'M = gbM
where b is the structure factor for the polymer.
This entity, which we call g-prime is the ratio of the Intrinsic Viscosity of the branched polymer to the linear polymer at the same molecular weight:
To determine the branching number for a branched polymer, we need to know its structure factor, decide which branching calculation to use and have some way of determining the IV of the linear sample at a given molecular weight. This can be determined either from the Mark-Houwink constants of the polymer, or by inspection from a linear reference sample.
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