GPC Test - Polymer Molecular Weight Characterization

Gel permeation chromatography (GPC) is a powerful analytical technique used to separate dissolved molecules by size through a column filled with a porous gel. This technique is described as a type of molecular sieving chromatography in which samples are separated into their constituent parts by dissolving the sample in a mobile phase and passing it through a porous column packing. Individual components move through the stationary phase at different speeds depending on their ability to enter different pores, causing the sample to separate in a process known as differential partitioning.

This technique, also called size exclusion chromatography, is widely used for the chemical analysis of large types of molecules (polymers) and also covers many biochemical applications. Gel permeation chromatography is the leading method for measuring molecular weight distributions of complex polymers.

To perform gel permeation chromatography, a solvent is first used to dissolve the sample. The liquid is then continuously pumped into an adsorbent bed of porous gel beads packed into a column. Smaller sample molecules spend more time passing through the porous structure of the column and take longer to pass through the stationary phase. Conversely, a larger sample molecule cannot pass through the relatively small pores and passes rapidly through the column. This property reflects the hydrodynamic volumes of individual molecules.

Due to the development of a wide range of specially designed porous polymer packages, it is possible to analyze an extremely wide range of molecular weights using gel permeation chromatography columns. Conventional chromatography packings are not suitable for the detection of large molecules as they are mostly retained in the solid porous structure and do not elute from the column.

Finely tuned porous resins increase the separation capacity of chromatography columns and can be tailored for improved resolution within a specific molecular weight range.

Gel permeation chromatography is today one of the most widely accepted methods for determining the molecular weight of polymer macromolecules. This method is a very effective method based on differences in molecular mass. Large molecules are removed from the pores of the gels and eluted first. Gel permeation chromatography separates molecules based on their difference in size. This technique is based on the penetration of molecules into the voids of a macroporous support, mostly made of hydrophilic gels. In general, molecules with a hydrodynamic diameter smaller than the diameter of the pores in the support diffuse into the matrix, while molecules with larger diameters are excluded and thus faster passage is achieved.

When talking about the molecular weight of polymers, we do not mention a specific weight value for a molecule, but generally an average weight value. Because the molecules that make up the polymer are not of the same chain length, and since chains of different molecular weights form the polymer, the molecular weight is expressed by taking an average value. In this case, the molecular weight distribution of polymers is also very important. Both the average molecular weight and molecular weight distribution of polymers are considered important as they affect the properties of the polymer material and directly determine the place of use.

The molecular weight of a polymer is the sum of the atomic weights of the individual atoms that make up a molecule. It shows the average length of the polymer chains of the bulk resin. Not all polymer molecules in a given class have exactly the same molecular weight. There is a range or distribution of molecular weights.

Polymer molecular weight is defined as a distribution rather than a specific number. Because polymerization occurs to produce different chain lengths. There are two ways to characterize polymer molecular weight: weight average molecular weight and number average molecular weight.

Among the numerous testing, measurement, analysis and evaluation studies provided to businesses by our organization, there are also GPC testing and polymer molecular weight characterization services.