- Degree of polymerization
For a homopolymer, there is only one type of monomeric unit and the number-average degree of polymerization is given by
For most industrial purposes, degrees of polymerization in the thousands or tens of thousands are desired.
Some authors, however, define DP as the number of repeat units, where for copolymers the repeat unit may not be identical to the monomeric unit. For example, in nylon-6,6, the repeat unit contains the two monomeric units —NH(CH2)6NH— and —OC(CH2)4CO— , so that a chain of 1000 monomeric units corresponds to 500 repeat units. The degree of polymerization or chain length is then 1000 by the first (IUPAC) definition, but 500 by the second.
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.
- ^ IUPAC Definition in Compendium of Chemical Terminology (IUPAC Gold Book)
- ^ Cowie J.M.G. "Polymers: Chemistry and Physics of Modern Materials" (2nd edn Blackie 1991), p.10
- ^ Allcock H.R., Lampe F.W. and Mark J.P. "Contemporary Polymer Chemistry" (3d edn Pearson Prentice-Hall 2003), p.316
- ^ Fried J.R. "Polymer Science and Technology" (Pearson Prentice-Hall, 2nd edn 2003), p.27
- ^ Rudin A. "Elements of Polymer Science and Engineering" (Academic Press 1982), p.7
- ^ Flory, P.J. and Vrij, A. J. Am. Chem. Soc.; 1963; 85(22) pp3548-3553
Wikimedia Foundation. 2010.
Look at other dictionaries:
degree of polymerization — polimerizacijos laipsnis statusas T sritis chemija apibrėžtis Monomero grandžių skaičius polimero makromolekulėje. atitikmenys: angl. degree of polymerization rus. степень полимеризации … Chemijos terminų aiškinamasis žodynas
Degree of polymerization — Степень полимеризации … Краткий толковый словарь по полиграфии
degree of polymerization — the average number of mer units per polymer chain molecule … Mechanics glossary
degree — of freedom degree of polymerization … Mechanics glossary
Polymerization — An example of alkene polymerization, in which each Styrene monomer unit s double bond reforms as a single bond with another styrene monomer and forms polystyrene. In polymer chemistry, polymerization is a process of reacting monomer molecules… … Wikipedia
Addition polymerization — nM (monomer) ightarrow ( M ) n (polymer)where n is the degree of polymerization.CharacteristicsThe main characteristics are:* polymerisation process takes place in three distinct steps: # chain initiation, usually by means of an initiator which… … Wikipedia
Emulsion polymerization — is a type of radical polymerization that usually starts with an emulsion incorporating water, monomer, and surfactant. The most common type of emulsion polymerization is an oil in water emulsion, in which droplets of monomer (the oil) are… … Wikipedia
Radical polymerization — is a type of polymerization in which the reactive center of a polymer chain consists of a radical.The polymerization reaction is initiated by three classes of free radical initiators: * certain compounds that can be broken down in two radicals at … Wikipedia
Polymer — Appearance of real linear polymer chains as recorded using an atomic force microscope on surface under liquid medium. Chain contour length for this polymer is 204 nm; thickness is 0.4 nm. A polymer is a large molecule (macromolecule … Wikipedia
Kinetic chain length — In polymer chemistry the kinetic chain length of a polymer, ν , is the average number of monomers added to each polymerizing radical during polymerization. During this process, a polymer chain is formed when units called monomers are bonded… … Wikipedia