Polymer fractionation: Difference between revisions

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Polymers are chainlike molecules that are made of the same repetition unit. With a few exceptions such as proteins, a polymer consists of a mix of molecules with different chain lengths. Therefore, average values are given for the molecular weight like the number average, the weight average or the viscosity average molar mass. A measure for the width of the molecular weight distribution is the polydispersity index. The targeted manipulation of the molecular weight distribution of a polymer by removing short and/or long chain material is called polymer fractionation.

Reasons for polymer fractionation

The molecular weight of polymers has a large influence on their properties and therefore determines the applications. Among others the flow behavior, the solubility, the mechanical properties but also the lifetime are influenced by the molecular weight. For high duty polymers – polymers that have to fulfill elevated demands – not only the molecular weight but also the molecular weight distribution is important. This especially holds true if low and/or high molecular material disturbs a given task.

Analytical methods

Polymers can be fractionated on an analytical scale by size exclusion chromatography (SEC), Matrix-assisted laser desorption/ionization (MALDI) or field flow fractionation (FFF). These methods are used to determine the molecular weight distribution.

Preparative methods

In most cases the fractionation of polymers on a preparative scale is based on chromatographic methods (e.g. preparative SEC or Baker-Williams fractionation). Therefore, the production is normally limited to few grams only. For large scales of several grams up to kg or even tons the “continuous spin fractionation” can be used. F. Francuskiewicz gives an overview about preparative polymer fractionation.

Literature

M.J.R Cantow Polymer Fractionation Academic Press, New York (1967)
L.H. Tung Fractionation of Synthetic Polymers Marcel Dekker, New York (1977)
F. Francuskiewicz Polymer Fractionation Springer, Berlin (1994)
R. Koningsveld, L.D. Kleintjens, H. Geerissen, P. Schützeichel, B.A. Wolf „Fractionation“ in: Comprehensive Polymer Science Volume 1 Pergamon Press, Oxford (1989) 293-312

External links

http://www.wee-solve.de - WEE-Solve GmbH: Service provider for polymer fractionation

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+{{Short description|Targeted manipulation of molecular weight distribution}}
-[[Polymer]]s are chainlike [[molecule]]s that are made of the same repetition unit. With a few exceptions such as [[protein]]s, a polymer consists of a mix of molecules with different chain lengths. Therefore average values are given for the [[molar mass|molecular weight]] like the [[Molar mass distribution#Number average molecular weight|number average]], the [[Molar mass distribution#Weight average molecular weight|weight average]] or the viscosity average molar mass. A measure for the width of the [[molar mass distribution|molecular weight distribution]] is the [[polydispersity index]]. The targeted manipulation of the molecular weight distribution of a polymer by removing short and/or long chain material is called '''polymer fractionation'''.
+[[Polymer]]s are chainlike [[molecule]]s that are made of the same repetition unit. With a few exceptions such as [[protein]]s, a polymer consists of a mix of molecules with different chain lengths. Therefore, average values are given for the [[molar mass|molecular weight]] like the [[Molar mass distribution#Number average molecular weight|number average]], the [[Molar mass distribution#Weight average molecular weight|weight average]] or the viscosity average molar mass. A measure for the width of the [[molar mass distribution|molecular weight distribution]] is the [[polydispersity index]]. The targeted manipulation of the molecular weight distribution of a polymer by removing short and/or long chain material is called '''polymer fractionation'''.
 == Reasons for polymer fractionation ==
 The molecular weight of polymers has a large influence on their properties and therefore determines the applications. Among others the flow behavior, the [[solubility]], the mechanical properties but also the lifetime are influenced by the molecular weight. For high duty polymers – polymers that have to fulfill elevated demands – not only the molecular weight but also the molecular weight distribution is important. This especially holds true if low and/or high molecular material disturbs a given task.
-== Analytical Methods ==
+== Analytical methods ==
-Polymers can be fractionated on an analytical scale by [[size exclusion chromatography]] (SEC), [[Matrix-assisted laser desorption/ionization]] (MALDI) or [[Field Flow Fractionation]] (FFF).  These methods are used to determine the molecular weight distribution.
+Polymers can be fractionated on an analytical scale by [[size exclusion chromatography]] (SEC), [[Matrix-assisted laser desorption/ionization]] (MALDI) or [[field flow fractionation]] (FFF).  These methods are used to determine the molecular weight distribution.
-== Preparative Methods ==
+== Preparative methods ==
-In most cases the fractionation of polymers on a preparative scale is based on chromatographic methods (e.g. preparative SEC or [[Baker-Williams fractionation]]). Therefore the production is normally limited to few grams only. For large scales of several grams up to kg or even tons the “Continuous Spin Fractionation” can be used. F. Francuskiewicz gives an overview about preparative polymer fractionation.
+In most cases the fractionation of polymers on a preparative scale is based on chromatographic methods (e.g. preparative SEC or [[Baker-Williams fractionation]]). Therefore, the production is normally limited to few grams only. For large scales of several grams up to kg or even tons the “continuous spin fractionation” can be used. F. Francuskiewicz gives an overview about preparative polymer fractionation.
 == Literature ==