aspects of column-based fractionations for the analysis of complex polymers is
given in a number of monographs [2–5].
For the molar mass analysis of polyolefins, high-temperature (HT) SEC has been
used routinely for more than 40 years [6–8]. The commercial versions of
corresponding HT chromatography instruments have been available since 1964.
Several detectors such as refractive index (RI), viscometer (Visco), light scattering
(LS) or infrared (IR) may be equipped with the instruments. Due to the niche
market of HT-SEC instruments, only a few types of instruments are available,
including the Agilent PL-GPC 220 [9], the Malvern/Viscotek HT-GPC [10] and the
GPCIR of Polymer Char [11].
SEC at elevated temperatures (HT-SEC) is a fast, reliable and precise method for
the measurement of molar mass averages, molar mass dispersity and the complete
molar mass distribution (MMD) of polyolefins. Different detectors and calibration
options can be added to modify the technique according to the complexity of the
samples [12, 13]. Different options include (1) conventional HT-SEC with a
concentration detector, (2) HT-SEC-LS and (3) HT-SEC-Visco. Three online
detectors are frequently used in a single SEC system, termed a triple-detector
SEC (TriSEC). In TriSEC, an online viscometer and a multiangle laser light
scattering (MALLS) instrument are coupled to SEC in addition to a concentration
detector such as RI. With TriSEC, absolute molar mass determination is possible
for polymers that are very different in chemical composition and molecular conformation. The usefulness of the TriSEC approach has been demonstrated in a number
of applications [14–20].
In this part, different modes of column-based chromatographic techniques for
the analysis of complex polyolefins will be discussed. Multidetector HT-SEC will
be used for molar mass analysis while chemical composition analysis will be
conducted using different modes of HT interaction chromatography. The multidimensional analysis of complex polyolefins by two-dimensional liquid chromatography (2D-LC) or the coupling with powerful spectroscopic detectors will be
presented.
3.1
Multidetector Size Exclusion Chromatography
As mentioned earlier, most polyolefins are soluble only at high temperatures. This
is a challenge for column-based chromatography because the complete system from
sample injection to the detector must be kept at high temperature to prevent the
polyolefin fractions from precipitating out of solution. Most polyolefins dissolve
only at temperatures above their melting points, usually between 110
C and
160
C. Accordingly, high boiling point solvents must be used, the most popular
being 1,2,4-trichlorobenzene (TCB), ortho-dichlorobenzene (ODCB), decalin,
methylcyclohexane, α-chloronaphthalene and tetrachloroethylene [21–24].
The severe operating conditions in HT-SEC affect not only the sample and the
mobile phase but also the stationary phase. It must withstand high temperatures for
extended periods of times (several years) without deteriorating or changing its
76
3 Column-Based Chromatographic Techniques
given in a number of monographs [2–5].
For the molar mass analysis of polyolefins, high-temperature (HT) SEC has been
used routinely for more than 40 years [6–8]. The commercial versions of
corresponding HT chromatography instruments have been available since 1964.
Several detectors such as refractive index (RI), viscometer (Visco), light scattering
(LS) or infrared (IR) may be equipped with the instruments. Due to the niche
market of HT-SEC instruments, only a few types of instruments are available,
including the Agilent PL-GPC 220 [9], the Malvern/Viscotek HT-GPC [10] and the
GPCIR of Polymer Char [11].
SEC at elevated temperatures (HT-SEC) is a fast, reliable and precise method for
the measurement of molar mass averages, molar mass dispersity and the complete
molar mass distribution (MMD) of polyolefins. Different detectors and calibration
options can be added to modify the technique according to the complexity of the
samples [12, 13]. Different options include (1) conventional HT-SEC with a
concentration detector, (2) HT-SEC-LS and (3) HT-SEC-Visco. Three online
detectors are frequently used in a single SEC system, termed a triple-detector
SEC (TriSEC). In TriSEC, an online viscometer and a multiangle laser light
scattering (MALLS) instrument are coupled to SEC in addition to a concentration
detector such as RI. With TriSEC, absolute molar mass determination is possible
for polymers that are very different in chemical composition and molecular conformation. The usefulness of the TriSEC approach has been demonstrated in a number
of applications [14–20].
In this part, different modes of column-based chromatographic techniques for
the analysis of complex polyolefins will be discussed. Multidetector HT-SEC will
be used for molar mass analysis while chemical composition analysis will be
conducted using different modes of HT interaction chromatography. The multidimensional analysis of complex polyolefins by two-dimensional liquid chromatography (2D-LC) or the coupling with powerful spectroscopic detectors will be
presented.
3.1
Multidetector Size Exclusion Chromatography
As mentioned earlier, most polyolefins are soluble only at high temperatures. This
is a challenge for column-based chromatography because the complete system from
sample injection to the detector must be kept at high temperature to prevent the
polyolefin fractions from precipitating out of solution. Most polyolefins dissolve
only at temperatures above their melting points, usually between 110
C and
160
C. Accordingly, high boiling point solvents must be used, the most popular
being 1,2,4-trichlorobenzene (TCB), ortho-dichlorobenzene (ODCB), decalin,
methylcyclohexane, α-chloronaphthalene and tetrachloroethylene [21–24].
The severe operating conditions in HT-SEC affect not only the sample and the
mobile phase but also the stationary phase. It must withstand high temperatures for
extended periods of times (several years) without deteriorating or changing its
76
3 Column-Based Chromatographic Techniques