several publications [43–47]. The complex structure of polyolefins has been
investigated by a combination of TREF and SEC-FTIR [48, 49]. The application
of the LC-Transform system for the analysis of complex polyolefins regarding
chemical composition by solvent gradient interaction chromatography will be
addressed in Sect. 3.2.1.
The challenges associated with the further improvement in sensitivity are related
to the loss of IR sensitivity in the reflectance mirrors of the optics module and the
deposition of the effluents in rather narrow tracks on the substrate. The configuration of the recently commercialized DiscovIR-LCTM interface by Spectra Analysis
Inc. (Marlborough, MA, USA) accounts for the energy loss in the optics module by
using IR microscopy [50]. This single unit instrument eliminates the solvent from
LC eluate and deposits the chromatogram as a track as a function of retention time.
The scanning of the track takes place by a built-in FTIR microscope in real time.
The oxidation of compounds is prevented by deposition under high vacuum and low
temperatures (À140 to 100
C). ZnSe is the deposition matrix, which allows
measurements in the transmission mode. Several applications of this interface
have been reported; however, so far none for the analysis of polyolefins.
3.1.3 Analysis of a Polymer Blend by Coupled SEC1
H NMR [51]
The direct coupling of high-temperature liquid chromatography to
1
H NMR is a
further advancement in the analysis of complex polyolefins. With the introduction
of a high-temperature flow-through NMR probe by Bruker, the equipment for such
a coupling became available. Hiller et al. elaborated details of the experimental
set-up and the construction of the LC-NMR interface [51]. Briefly, the workable
operating temperature of the probe was now enhanced to 150
C. The active flow
cell in the probe has a volume of 120 μL. It is a dual inverse
1 H/
13 C probe with
pulsed field gradients. At the interface of SEC and NMR, a two-position stop-flow
valve is mounted. The valve directs the flow from the SEC to the NMR or to waste,
as can be seen in Fig. 3.6. On-flow experiments, automatic stop-flow experiments
and time slicing are possible with this set-up.
3.1.3.1 Aim
The HT-SEC-NMR method shall be used for the separation and analysis of a
ternary polymer blend comprising two homopolymers and the corresponding
copolymer. SEC shall separate the components by molar mass while
1 H-NMR
shall provide identification and structural details of the components.
3.1.3.2 Materials
• Polymers. Two samples of PE with number average molar masses of
1,100 g/mol (M w /M n ¼ 1.1) and 60,000 g/mol (M w /M n ¼ 1.5), respectively, one
sample of PMMA with a number average molar mass of 263,000 g/mol
(M w /M n ¼ 1.06), and one sample of poly[(ethylene)-co-(methyl methacrylate)]
(PE-PMMA) with a number average molar mass of 10,600 g/mol (M w /M n ¼ 2.3).
3.1 Multidetector Size Exclusion Chromatography
85
investigated by a combination of TREF and SEC-FTIR [48, 49]. The application
of the LC-Transform system for the analysis of complex polyolefins regarding
chemical composition by solvent gradient interaction chromatography will be
addressed in Sect. 3.2.1.
The challenges associated with the further improvement in sensitivity are related
to the loss of IR sensitivity in the reflectance mirrors of the optics module and the
deposition of the effluents in rather narrow tracks on the substrate. The configuration of the recently commercialized DiscovIR-LCTM interface by Spectra Analysis
Inc. (Marlborough, MA, USA) accounts for the energy loss in the optics module by
using IR microscopy [50]. This single unit instrument eliminates the solvent from
LC eluate and deposits the chromatogram as a track as a function of retention time.
The scanning of the track takes place by a built-in FTIR microscope in real time.
The oxidation of compounds is prevented by deposition under high vacuum and low
temperatures (À140 to 100
C). ZnSe is the deposition matrix, which allows
measurements in the transmission mode. Several applications of this interface
have been reported; however, so far none for the analysis of polyolefins.
3.1.3 Analysis of a Polymer Blend by Coupled SEC1
H NMR [51]
The direct coupling of high-temperature liquid chromatography to
1
H NMR is a
further advancement in the analysis of complex polyolefins. With the introduction
of a high-temperature flow-through NMR probe by Bruker, the equipment for such
a coupling became available. Hiller et al. elaborated details of the experimental
set-up and the construction of the LC-NMR interface [51]. Briefly, the workable
operating temperature of the probe was now enhanced to 150
C. The active flow
cell in the probe has a volume of 120 μL. It is a dual inverse
1 H/
13 C probe with
pulsed field gradients. At the interface of SEC and NMR, a two-position stop-flow
valve is mounted. The valve directs the flow from the SEC to the NMR or to waste,
as can be seen in Fig. 3.6. On-flow experiments, automatic stop-flow experiments
and time slicing are possible with this set-up.
3.1.3.1 Aim
The HT-SEC-NMR method shall be used for the separation and analysis of a
ternary polymer blend comprising two homopolymers and the corresponding
copolymer. SEC shall separate the components by molar mass while
1 H-NMR
shall provide identification and structural details of the components.
3.1.3.2 Materials
• Polymers. Two samples of PE with number average molar masses of
1,100 g/mol (M w /M n ¼ 1.1) and 60,000 g/mol (M w /M n ¼ 1.5), respectively, one
sample of PMMA with a number average molar mass of 263,000 g/mol
(M w /M n ¼ 1.06), and one sample of poly[(ethylene)-co-(methyl methacrylate)]
(PE-PMMA) with a number average molar mass of 10,600 g/mol (M w /M n ¼ 2.3).
3.1 Multidetector Size Exclusion Chromatography
85