Chapter 9: Reaction Mechanisms, Pathways, Bioreactions and Bioreactors
Example 9.2: Calculate the Mean Molecular Weight
Calculate the mean molecular weight of a system that contains 95 wt % of polymer A with a molecular weight of 10,000 and 5% of polymer B with a molecular weight of 100.
Solution
1. Weight average molecular weight \( \overline{M}_w \)
\( \overline{M}_w = \sum w_i M_i = w_A M_A + w_B M_B \)
\( = (0.95)(10000) + (0.05)(100) = 9505 \)
\( \overline{M}_w = 9505 \) Weight average molecular weight
2. Number average molecular weight \( \overline{M}_n \)
\( \overline{M}_n = \sum y_i M_i = y_A M_A + y_B M_B \)
\( \overline{M}_n = 1684 \) Number average molecular weight