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Assume that I want to react A with repeating units of the polymer with ratio of 1:1. That is, I want to calculate that if I have $M_A$ mol of A, then what grams of polymer will I need to afford $M_A$ mol of repeating units.

Let $M_w$ be average molecular weight of given polymer and $M_u$ be molecular weight of repeating unit. To approximately calculate that what moles of repeating units is in one mole of polymer, I divided $M_w$ by $M_u$. That is, There are approximately $\frac{M_w}{M_u}$ moles of repeating units in one mole of polymer.

To calculate that what moles of polymer contains $M_A$ moles of repeating units, I used below proportional expression.

$\frac{M_w}{M_u}:1=M_A:x$

Then I get $x=\frac{M_uM_A}{M_w}$. That is, there are $M_A$ moles of repeating unit in $\frac{M_uM_A}{M_w}$ moles of polymer. To calculate grams of polymer I need, I multipy $x$ by $M_w$, and I get the grams of polymer I need is $M_uM_A$. This result is a little bit weird. The grams of polymer I need is independent of average molecular weight of polymer, $M_w$. Is it true? Did I make some mistakes?

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