Gel permeation chromatography GPC , also known as size exclusion chromatography SEC , is a widely used technique for determining the molecular weight distribution of a polymer sample. It works by separating polymer chains based on their size in solution, which is related to their molecular weight.Here's how GPC can be used to determine the molecular weight distribution of a polymer sample:1. A polymer sample is dissolved in an appropriate solvent to create a polymer solution.2. The polymer solution is injected into a GPC column packed with porous gel particles.3. As the solution flows through the column, smaller polymer chains can enter the pores of the gel particles, while larger chains are excluded. This causes the larger chains to elute from the column first, followed by smaller chains.4. A detector, typically a refractive index or UV detector, measures the concentration of the eluting polymer chains as a function of elution time or volume.5. The elution time or volume is then converted to molecular weight using a calibration curve generated from a set of polymer standards with known molecular weights.6. The resulting data is used to calculate the molecular weight distribution of the polymer sample, including parameters such as number-average molecular weight Mn , weight-average molecular weight Mw , and polydispersity index PDI .Advantages of GPC compared to other polymer characterization techniques:1. GPC is a relatively fast and straightforward method for determining molecular weight distribution.2. It is a non-destructive technique, meaning that the polymer sample is not altered during the analysis.3. GPC can be used for a wide range of polymer types and molecular weights.4. The technique can be easily automated, allowing for high-throughput analysis.Limitations of GPC:1. GPC requires the use of calibration standards, which may not always accurately represent the sample being analyzed. This can lead to errors in the calculated molecular weights.2. The technique is sensitive to the choice of solvent and column packing material, which may affect the separation and molecular weight determination.3. GPC does not provide information on the chemical structure or composition of the polymer, unlike techniques such as nuclear magnetic resonance NMR or mass spectrometry MS .4. The accuracy of GPC can be affected by sample preparation, such as incomplete dissolution or the presence of impurities.5. GPC is generally limited to soluble polymers, as insoluble or highly cross-linked polymers cannot be analyzed using this technique.