Details

The number fraction and weight fraction of polymer chains for a polymer with monomer units are:

,

,

where is mole fraction and is the fraction of functional groups that have reacted:

.

For step-growth polymerization:

,

.

For free-radical polymerization:

,

,

where and are the initial monomer and initiator concentrations; is monomer concentration; , and are the rate constants for the reaction, initiation and termination; is time; is the terminator concentration and is fraction of chains initiated by initiator.

The number and weight average chain lengths are:

,

,

where is the polymer concentration.

The polydispersity is:

.

Reference

[1] H. S. Fogler, Elements of Chemical Reaction Engineering, 5th ed., Boston: Prentice Hall, 2016.