Molecular Weight and Degree

Molecular weight of a polymer #

There are different types of molecular weights of polymers

$N_i$: Number of molecules of mass $M_i$

$$ M_n = \frac{w}{\sum N} = \frac{\sum N_i M_i}{\sum N_i} $$

$w_i$: weight fraction of molecules having mass $M_i$ $$ M_w = \frac{\sum w_i M_i}{\sum w_i} = \frac{\sum N_i M_i^2}{\sum N_i M_i} $$

P.D.I. = $\frac{M_w}{M_n}$

PDI>1.5 for natural and synthetic polymers PDI=1 in case all the polymer molecules are of identical molecular weight.

DP: The number of recurring units of monomers in a polymer chain.

M: Concentration of monomer C: Concentration of initiator

$-\frac{dM}{dt}=k[M][C]^{1/2}$

Degree of polymerization when # active centers=# chain terminators

$DP=\frac{k[M]}{[C]^{1/2}}$