Question

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

Answer 1

For natural polymer, PDI (polymer dispersity index) is equal because they are typically uniform and straight in length. Natural polymers are those polymers which occur naturally and are extracted from plants or animals. Natural polymers play a very crucial role in our daily life and no one can survive without their existence.

Complete step by step answer:
Macromolecules are the “giant” molecules (polymers) formed when small organic molecules (monomers) are joined in a biological medium. Example: proline due to the joining of many monomer units, the molecule has high molecular weight and viscosity.
Macromolecules have a molar mass distribution due to the simplest homopolymers made of homologue chains with a different number of repeating units.
They exhibit average values of two types:
Number of average molar mass $\left[ {{M_n}} \right]$
Weight average molar mass $\left[ {{M_w}} \right]$
The ratio of these average values give the polymer disparity index) = ${\dfrac{{M_w}} {{M_n}}}$
${M_n}$ and ${M_w}$ depends upon the polymer chains of definite molar mass.
In short, we can understand this as,
PDI or Polydispersity index is the ratio of mass average molecular mass to the number average molecular mass. When PDI value is one, it indicates the monodispersity or given polymer has monomers arranged in chains of equal length.
Synthetic polymers are usually less homogeneous and so their PDI is greater than 1. So, in the given option, cellulose is a natural polymer, hence its ODI poly disparity index is equal to $1$.

So, the correct answer is Option C.

Note:
Polydispersity Index (PDI) is used to measure the broadness of molecular weight distribution. The larger the PDI, the broader the molecular weight.
The polydispersity index (PDI) of the polymer is always $1$ or$> 1$. It cannot be$< 1$. It is a measure of distribution of molecular mass in a given polymer sample.