By Oxana Fox – Updated Mar 24, 2022
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The degree of polymerization (DP) is a key metric that governs the mechanical, thermal, and rheological properties of polymeric materials. It represents the number of repeating monomer units that make up a polymer chain and is calculated as the ratio of the polymer’s molecular weight to that of its monomeric repeat unit.
Start by writing the polymer’s structural formula. For example, a polymer derived from tetrafluoroethylene is represented as [-(CF₂–CF₂)ₙ]ₙ, where the monomer unit (CF₂–CF₂) is placed inside parentheses.
Retrieve the atomic masses of the elements that compose the monomer from a reliable periodic table source. For tetrafluoroethylene, the masses are carbon (C) = 12 Da and fluorine (F) = 19 Da.
Multiply each element’s atomic mass by its count in the monomer unit and sum the results. Using the tetrafluoroethylene example:
12 Da × 2 + 19 Da × 4 = 100 Da
Divide the polymer’s measured molecular weight by the monomer’s molecular weight. If a tetrafluoroethylene polymer has a molecular mass of 120,000 Da, the DP is:
120,000 Da ÷ 100 Da = 1,200
