Degree of polymerization

The degree of polymerization, or DP, is the number of monomeric units in a macromolecule or polymer or oligomer molecule.

[1][2][3] For a homopolymer, there is only one type of monomeric unit and the number-average degree of polymerization is given by

The degree of polymerization or chain length is then 1000 by the first (IUPAC) definition, but 500 by the second.

, a high fractional monomer conversion, p, is required, according to Carothers' equation[6][7]

For chain-growth free radical polymerization, however, Carothers' equation does not apply.

Long reaction times increase the polymer yield, but have little effect on the average molecular weight.

[8] The degree of polymerization is related to the kinetic chain length, which is the average number of monomer molecules polymerized per chain initiated.

Synthetic polymers invariably consist of a mixture of macromolecular species with different degrees of polymerization and therefore of different molecular weights.

[4] The number-average degree of polymerization is a weighted mean of the degrees of polymerization of polymer species, weighted by the mole fractions (or the number of molecules) of the species.

It is typically determined by measurements of the osmotic pressure of the polymer.

It is typically determined by measurements of Rayleigh light scattering by the polymer.