Degree of polymerization
From Wikipedia, the free encyclopedia
The degree of polymerization, or DP, is the number of repeat units in an average polymer chain at time t in a polymerization reaction [1]. 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 below
DP = Total MW of the polymer/MW of the repeating unit
- Mn = XnMo
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.
[edit] 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 [2] and higher mechanical strength.
