Question

Polydispersity index for polymers represents?

• A. A measure of the number of molecular chains in a polymer.
• B. A measure of the variance in the molecular chain lengths and weights in a synthetic polymer.
• C. It is a quantity to determine the average molecular mass of a natural polymer.
• D. It gives us the number of molecules of the same size in a polymer.

Answer 1

The correct option is B A measure of the variance in the molecular chain lengths and weights in a synthetic polymer.

The polydispersity index (PDI) is a measure of the heterogeneity of the molecular chains in a polymer.

When artificially synthesize polymers using catalysts, we are not able to achieve a perfect long chain of molecules.

We will get a mixture of relatively large chains as compared to monomers. But even these chains of molecules are not equal in length and are not of the same weight. It is usually a mixture of chains of different lengths and weights.

So, we need a measure to understand how much these chains vary and PDI is a measure of the degree of this variance.

Note: Natural polymers like proteins are monodisperse, PDI = 1