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If $\bar{M}_w$ is the weight average molecular weight and $\bar{M}_n$ is the number average molecular weight of a polymer, the poly dispersity index (PDI) of the polymer is given by
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The correct answer is:
$\frac{\bar{M}_w}{\bar{M}_n}$
The ratio of weight average molecular weight and the number average molecular weight is called poly dispersity index (PDI).
$$
\mathrm{PDI}=\frac{\bar{M}_w}{\bar{M}_n}
$$
where,
$\bar{M}_w=$ weight average molecular weight
$\bar{M}_n=$ number average molecular weight
PDI is unity for natural monodispersed polymer but for synthetic polymers it is always greater than unity.
$$
\mathrm{PDI}=\frac{\bar{M}_w}{\bar{M}_n}
$$
where,
$\bar{M}_w=$ weight average molecular weight
$\bar{M}_n=$ number average molecular weight
PDI is unity for natural monodispersed polymer but for synthetic polymers it is always greater than unity.
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