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Degree of polymerization
The degree of polymerization, or DP, is the number of repeat units in an average polymer chain at time t in a polymerization reaction . The length is in monomer units. The degree of polymerization is a measure of molecular weight. For most industrial purposes, lengths in the thousands or tens of thousands are desired.
For a homopolymer, the degree of polymerization may be calculated as shown bellow
DP = Total MW of the polymer/MW of the repeating unit
In polycondensation, in order to achieve a high degree of polymerization (and hence molecular weight), Xn, a high fractional monomer conversion, p, is required, as per Carothers' equation: Xn = 1/(1−p). A monomer conversion of p = 99% would be required to achieve Xn = 100.
Correlation with physical properties
Polymers with identical composition but different total molecular weights may exhibit different physical properties. In general, increasing degree of polymerization correlates with higher melting temperature  and higher mechanical strength.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Degree_of_polymerization". A list of authors is available in Wikipedia.|