Question

Which of the following has PDI value $1$ ?
A. Dacron
B. SBR
C. Cellulose
D. PVC

Answer 1

The value of PDI, that is, polymer dispersity index, for natural polymer is equal to $1$ , because they are uniform and straight in length. Natural polymers are defined as the polymers that occur naturally from plants and animals.

Complete answer:
Polymer dispersity index is defined as the ratio of weight average molecular mass to the number average molecular mass. Natural polymers are typically uniform and straight in length. When the polymer dispersity index is equal to $1$ , it indicates that the weight average molecular is equal to the number average molecular mass. When the polymer dispersity index (PDI) value is one, it shows monodispersity, and the polymers have monomers that are arranged in chains of equal length.
In the given question we have seen that, cellulose is the only natural polymer, whereas all the above polymers except cellulose, are synthetic or man – made. Synthetic polymers have polymer dispersity index value greater than one, because they are usually less homogeneous.
So, the correct answer is “Option C”.

Additional Information:
-When monomers are joined together to form polymers, they form giant molecules, known as macromolecules. Macro molecules exhibit average values of two types:
-Weight average molecular mass
-Number average molar mass
-Polymer dispersity index is the ratio of these average values.
$PDI=\dfrac{{{M}_{w}}}{{{M}_{n}}}$
where, ${{M}_{w}}$ is the weight average molecular mass and ${{M}_{n}}$ is the number average molecular mass.

Note:
-Monodispersity is defined as the uniformity in the shape and size of an object. In this question, cellulose shows monodispersity.
-Cellulose is a natural polymer which occurs naturally in cell walls of the plants.