Column-Based Chromatographic
Techniques
3
Crystallization-based fractionation techniques are powerful methods for the chemical composition fractionation of semi-crystalline polyolefins. The crystallizing
components are fractionated according to their crystallizability, which for
copolymers is a function of copolymer composition. The non-crystallizing part
cannot be fractionated and is obtained as a bulk fraction (‘soluble fraction’).
Crystallization-based fractionation techniques are far less sensitive to molar mass
than they are to chemical composition. In the past, different methods of temperature
and solvent–nonsolvent based fractionations have been used, as summarized by
Francuskiewicz [1].
In contrast to crystallization-based fractionation techniques, liquid chromatography (LC) exploits specific interactions of the analyte with the separation medium
to achieve a separation according to molar mass, chemical composition or molecular topology. In the case of LC, the separation medium is a stationary phase. An
alternative is field-flow fractionation (FFF), where the separation medium is a
channel that is exposed to an external field.
In column- and channel-based fractionation techniques, the sample is
completely dissolved in a suitable solvent (the mobile phase) and then injected
into the separation medium. There, the sample may precipitate or remain in
solution. In any case, the separation is based on the interaction of all analyte
molecules with the separation medium irrespective of crystallinity. Different from
crystallization-based fractionation, in column- or channel-based fractionations all
components of the analyte are separated regarding specific molecular parameters.
Column-based fractionation techniques have been used in polymer analysis for
more than 60 years. First, size exclusion chromatography (SEC) was introduced,
followed by different methods of interaction chromatography. The former separates
according to hydrodynamic volume of polymer species in solution, therefore
providing information on molecular size and molar mass. In contrast, the latter is
used mainly for separations according to chemical composition, functionality and
molecular topology. Extensive information on the theory and the experimental
# Springer International Publishing Switzerland 2014
H. Pasch, M.I. Malik, Advanced Separation Techniques for Polyolefins, Springer
Laboratory, DOI 10.1007/978-3-319-08632-3_3
75
Techniques
3
Crystallization-based fractionation techniques are powerful methods for the chemical composition fractionation of semi-crystalline polyolefins. The crystallizing
components are fractionated according to their crystallizability, which for
copolymers is a function of copolymer composition. The non-crystallizing part
cannot be fractionated and is obtained as a bulk fraction (‘soluble fraction’).
Crystallization-based fractionation techniques are far less sensitive to molar mass
than they are to chemical composition. In the past, different methods of temperature
and solvent–nonsolvent based fractionations have been used, as summarized by
Francuskiewicz [1].
In contrast to crystallization-based fractionation techniques, liquid chromatography (LC) exploits specific interactions of the analyte with the separation medium
to achieve a separation according to molar mass, chemical composition or molecular topology. In the case of LC, the separation medium is a stationary phase. An
alternative is field-flow fractionation (FFF), where the separation medium is a
channel that is exposed to an external field.
In column- and channel-based fractionation techniques, the sample is
completely dissolved in a suitable solvent (the mobile phase) and then injected
into the separation medium. There, the sample may precipitate or remain in
solution. In any case, the separation is based on the interaction of all analyte
molecules with the separation medium irrespective of crystallinity. Different from
crystallization-based fractionation, in column- or channel-based fractionations all
components of the analyte are separated regarding specific molecular parameters.
Column-based fractionation techniques have been used in polymer analysis for
more than 60 years. First, size exclusion chromatography (SEC) was introduced,
followed by different methods of interaction chromatography. The former separates
according to hydrodynamic volume of polymer species in solution, therefore
providing information on molecular size and molar mass. In contrast, the latter is
used mainly for separations according to chemical composition, functionality and
molecular topology. Extensive information on the theory and the experimental
# Springer International Publishing Switzerland 2014
H. Pasch, M.I. Malik, Advanced Separation Techniques for Polyolefins, Springer
Laboratory, DOI 10.1007/978-3-319-08632-3_3
75