Q. If $M_{w}$ is the weight average molecular weight and ${\overline{M}}_{n}$ is the number of average molecular weight of a polymer, the poly dispersity index (PDI) of the polymer is given by
A) $\frac{{\overline{M}}_{n}}{M_{w}}$
B) $\frac{{\overline{M}}_{w}}{M_{n}}$
C) ${\overline{M}}_{w} \times {\overline{M}}_{n}$
D) $\frac{1}{{\overline{M}}_{w} \times {\overline{M}}_{n}}$
Explanation
(b)
The ratio of weight average molecular weight and the number average molecular weight is called poly dispersity index.
(PDI).
$PDI = \frac{{\overline{M}}_{w}}{{\overline{M}}_{n}}$
Where,
${\overline{M}}_{w}\ =$weight average molecular weight
${\overline{M}}_{n} =$ number average molecular weight
PDI is unity for natural monodispersed polymer but for synthetic polymers it is always greater than unity.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.