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Degree of polymerization

 

 
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Degree of polymerization
 
 
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The degree of polymerization, or DP, is the number of repeat units in an average polymer
Polymer

A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties....
 chain at time t in a polymerization
Polymerization

In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymer chains....
 reaction . The length is in monomer
Monomer

A monomer is a small molecule that may become Chemistry chemical bonding to other monomers to form a polymer....
 units. The degree of polymerization is a measure of molecular weight (MW). 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



In polycondensation
Condensation reaction

A condensation reaction is a chemical reaction in which two molecules or moieties combine to form one single molecule, together with the loss of a small molecule....
, 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).






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The degree of polymerization, or DP, is the number of repeat units in an average polymer
Polymer

A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties....
 chain at time t in a polymerization
Polymerization

In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymer chains....
 reaction . The length is in monomer
Monomer

A monomer is a small molecule that may become Chemistry chemical bonding to other monomers to form a polymer....
 units. The degree of polymerization is a measure of molecular weight (MW). 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



In polycondensation
Condensation reaction

A condensation reaction is a chemical reaction in which two molecules or moieties combine to form one single molecule, together with the loss of a small molecule....
, 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.

See also

  • Carothers equation
  • Kinetic chain length
    Kinetic chain length

    In polymer chemistry the kinetic chain length of a polymer, ? , is the average number of monomers added to each polymerizing radical during polymerization....