How to Calculate the Degree of Polymerization

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A degree of polymerization is a key characteristic of polymers that determine physical properties of polymer materials. Polymers are large molecules that consist of repeating structural (monomer) units. For example, polyethylene is composed of repeating units (CH2-CH2)n where “n” is an integer number that indicates the degree of polymerization. Mathematically, this parameter is a ratio of the molecular weights of the polymer and the respective monomer unit.

  1. Write Down the Chemical Formula

  2. Write down the chemical formula.of the polymer For example, if the polymer is tetrafluoroethylene then its formula is -(CF2-CF2)n -. The monomer unit is placed in parentheses.

  3. Get the Atomic Masses

  4. Obtain atomic masses of the elements that compose the monomer unit molecule, using the periodic table of elements. For tetrafluoroethylene, the atomic masses of carbon (C) and fluorine (F) are 12 and 19, respectively.

  5. Calculate Molecular Weight

  6. Calculate the molecular weight of the monomer unit by multiplying the atomic mass of each element by the number of atoms in the monomer of each, then add the products. For tetrafluoroethylene, the molecular weight of the monomer unit is 12 x 2 + 19 x 4 = 100.

  7. Divide to Get Degree of Polymerization

  8. Divide the molecular weight of the polymer by the molecular weight of the monomer unit to calculate the degree of polymerization. If the molecular mass of tetrafluoroethylene is 120,000, its degree of polymerization is 120,000 / 100 = 1,200.

References

  • "Chemistry: Textbook"; Raymond Chang; 2007

About the Author

Oxana Fox is a freelance writer specializing in medicine and treatment, computer software and hardware, digital photography and financial services. She graduated from Moscow Medical College in 1988 with formal training in pediatrics.

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