Introduction
The physical properties and behavior of polymers depends strongly on the properties of the polymer molecules themselves. This in turn means that the polymer properties will also have an impact on the properties of finished products made from or containing polymers. The molecular weight and molecular weight distribution, molecular size, intrinsic viscosity and structure all affect how the polymer material will behave. The most common tool used to investigate these aspects of synthetic polymers is gel-permeation or size-exclusion chromatography (GPC/SEC). The principle of GPC involves separating the sample as it travels through a porous but inert chromatography column matrix. While smaller molecules penetrate the pores more deeply, larger molecules are excluded and thus travel through the column faster. The result is a separation based on hydrodynamic volume. The basic data is simply a concentration profile of the size-separated sample but by using a multi-detector GPC system that combines light scattering, refractive index (RI), ultraviolet (UV) and intrinsic viscosity detectors, a large amount of information about a sample can be determined simultaneously.This includes the powerful and useful Mark-Houwink plot, which is a structure-molecular weight relationship generated by plotting the molecular weight (MW) directly measured from the light scattering detector against the intrinsic viscosity (IV) directly measured from the viscometer detector. In this application note, the structural distributions of some common polymers are compared using the Mark-Houwink plot. The data are all generated using the Malvern OMNISEC system.
Materials and methods
Samples were separated using two Viscotek T6000M columns. The mobile phase was THF stabilized with 300 ppm BHT. Samples were allowed to dissolve overnight to ensure full dissolution. The OMNISEC system was set up as follows:- Flow rate: 1.0 mL/min
- Autosampler temperature: 15 °C
- Column oven temperature: 35 °C
- Detectors temperature: 35 °C
Results
All four polymers are easily and successfully chromatographed under these conditions and shown in a triple chromatogram of all four of the samples, in each case including the low angle light scattering (LALS), RI and viscometer signals. The four RI chromatograms are overlaid to show the elution profiles and to highlight the differences between the polymers. Click here to see the application with the details of the results.Malvern provides the materials and biophysical characterization technology and expertise that enables scientists and engineers to investigate, understand and control the properties of dispersed systems. These systems range from proteins and polymers in solution, particle and nanoparticle suspensions and emulsions, through to sprays and aerosols, industrial bulk powders and high concentration slurries. Used at all stages of research, development and manufacturing, Malvern’s instruments provide critical information that helps accelerate research and product development, enhance and maintain product quality and optimize process efficiency. Our products reflect Malvern’s drive to exploit the latest technological innovations. They are used by both industry and academia, in sectors ranging from pharmaceuticals and biopharmaceuticals to bulk chemicals, cement, plastics and polymers, energy and the environment. Malvern systems are used to measure particle size, particle shape, zeta potential, protein charge, molecular weight, mass, size and conformation, rheological properties and for chemical identification, advancing the understanding of dispersed systems across many different industries and applications. www.malvern.com Material relationships http://www.malvern.com/en/
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