Question 17 (Textile Technology & Fibre Science)
Polydispersity index of a polymer is 5 and its weight average molecular weight is 8400 g/mol. The number average molecular weight (g/mol) of the polymer (in integer) is ___________.
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Here given,
Polydispersity index of a polymer=5
Weight average molecular weight(g/mol) of polymer=8400 g/mol
Number average molecular weight(g/mol) of polymer=?
Now by formula,
Polydispersity index=Weight average molecular weight(Mw)/Number average molecular weight(Mn)
5=8400/Mn
Mn=8400/5
Mn=1680
i.e. ,Number average molecular weight(Mn)=1680 g/mol (Answer)
Frequently Asked Questions | FAQs
What is Polydispersity index ?
The polydispersity index (PDI) is a measure of the distribution of molecular weight in a polymer sample. It is defined as the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) in a polymer sample. The PDI is a dimensionless parameter that provides information on the breadth of the molecular weight distribution in a polymer sample.
The PDI ranges from 1 (indicating a monodisperse sample, where all molecules have the same weight) to greater than 1 (indicating a polydisperse sample, where molecules have a broad range of weights). The higher the PDI, the broader the distribution of molecular weights in the sample, indicating a higher degree of heterogeneity in the sample.
The PDI is an important parameter in polymer science and engineering, as it can affect the physical and mechanical properties of a polymer, such as viscosity, melt flow, and tensile strength. The PDI is also important in polymer processing, as it affects the processing and performance of the polymer in various applications.