© Fraunhofer LBF MULTIDIMENSIONAL LIQUID CHROMATOGRAPHY FOR QUALITY CONTROL AND MATERIAL DEVELOPMENT Robert Brüll, Tibor Macko, Jan Arndt, Nico Apel Fraunhofer-Institute for Structural Durability and System Reliability LBF www.lbf.fraunhofer.de
© Fraunhofer LBF
MULTIDIMENSIONAL LIQUID CHROMATOGRAPHY FOR QUALITY CONTROL AND MATERIAL DEVELOPMENT
Robert Brüll, Tibor Macko, Jan Arndt, Nico ApelFraunhofer-Institute for Structural Durability and System Reliability LBFwww.lbf.fraunhofer.de
© Fraunhofer LBF
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Outline
� LC of Polycarbonate
� Graphite as Stationary Phase
� LC of Elastomers
� Choice of Detection
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Challenges in Polymer Analysis
LAC GPC
� Multidimensional techniques are required to analyze the chemical heterogeneity
� Classical: fractionations
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Multidimensional Liquid Chromatography
� Scheme of the instrument
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�
Poly(bisphenol A carbonate)Typical molecular metrics
Photo: N. Apel Photo: N. Apel
© Fraunhofer LBF
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Size-exclusion chromatographyBasic separation principle
� Size-exclusion effect: macromolecules permeatein pores of the stationary phase
� Larger molecules are partially excluded from pores
� Inverse sieve effect based on entropic processes
molar masses� � elution volume�
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Molar mass
molar mass� � degree of branching�
Triple-detection SEC (TD-SEC)
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Liquid adsorption chromatography (LAC)Basic separation principle
� Each repeating unit can interact with column
� molar masses� � elution volume�
� Separation according to molar massand chemical composition
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Liquid chromatography under critical conditions (LCCC)Basic separation principle
� Size-exclusion effects and interactions are balanced out
� Polymer backbone becomes “invisible”
� Separation according to end-groups or branching units is possible
� Separation is possible according to branching based on end-group moiety or branching units of the polymer
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Solvent gradient at near-critical conditions (SG-NCC)Poly(bisphenol A carbonate)
� New LC method developed:solvent gradient applied nearthe critical conditions
� PC1 � End-capped + linear
� PC2 � Un-capped + linear
� PC3 � Un-capped + branched
� Separation according to end-groupsand branching indicated
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Solvent gradient at near-critical conditions (SG-NCC)Fractionation
Separation according to branched structures indicated
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Two-dimensional liquid chromatography (2D-LC)
� 1D: Solvent gradient at near-critical conditions (SG-NCC)
� 2D: Size-exclusion chromatography (SEC)
� Improvement in separation: chemical structure and molar mass
� Comprehensive analysis of branched structures
Photo: N. Apel
© Fraunhofer LBF
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Un-capped + branched
Separation according to branched structures
Two-dimensional liquid chromatography (2D-LC)
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Coupling of triple-detection to 2D-LC
1. Determination of absolute molar masses
2. Determination of the degreeof branching in single spots
3. Comparison between concentration and branching profile
Detailed information on branched structures
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Summary
� TD-SEC: Monitoring of branching along the molar mass distribution
� SG-NCC: Separation according to end-capping level and branching
� 2D-LC: Individually separated linear and branched end-group species
� 2D-LC with TD-SEC: Detailed determination on branching parameters for individual branched species
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Graphite – A Structure Selective Stationary Phase
R RR Rm
r
o p
cis trans
� Stable up to 200 °C
� pH 0 – 14
� Well suitable in aqueous environments
� Multiple injections approach possible
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Separation according to Composition and Microstructure
0 5 10 15 20 25
0.0
0.2
0.4
0.6
0.8
1.0
isotactic PP
PE
syndio-
tactic PP
resp
on
se o
f E
LS
D [
Vo
lts]
elution time [minutes]
atactic PP
Start of gradient
A. de Groot et al. US 8076147BT. Macko, H. Pasch, Macromolecules, 2009 42 (16), 6063R. Chitta, T. Macko, R. Brüll, G. Kalies, J. Chrom. A, 2010, 1217(49) 7717 – 7722R. Cong, A. deGroot et al. Macromolecules 2011, 44, 3062 R. Brüll, A. Albrecht, Nachrichten aus der Chemie, 2009, 57, 152 – 154R. Chitta, T. Macko, R. Brülll, R. Cong, M. Miller, A. de Groot, J. Sep. Sci. 2013, 36(13) 2063
Stationary Phase: Hypercarb™ Mobile Phase: Decanol→TCB
� Separation according to composition and microstructure is possible
© Fraunhofer LBF
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Solvent gradient interactive chromatography
Hypercarb, 2-ethyl-1-hexanol�TCB, 160 oC
Difference 0.4 mol %!
R. Chitta, T. Macko, R. Brüll, Ch. Boisson, E. Cossoul, O. Boyron, Macromol. Chem. & Phys. 2015, 216, 721
10 11 12
0,0
0,5
1,0
Ethylene/1-hexene copolymers
20.7 mol%
13.9 mol%9 mol%
6.3 mol%5.8 mol%
5.1 mol%3.7 mol%
2.2 mol% 1.1 mol%
0.4 mol%
EL
SD
sig
nal [V
]
Elution volume [mL]
PE 260
kg/mol
0 mol%
0 2 4 6 8 10 12 14 16 18 20 2210,0
10,5
11,0
11,5
12,0
12,52-ethyl-1-hexanol-->TCB, Hypercarb 100 x4.6 mm
C18C8
C6
Elu
tio
n v
olu
me
[m
L]
Comonomer content [mol %]
ethylene-propene
ethylene-hexene
ethylene-octene
ethylene-octadecene
C3
Linear dependence between the elution volume and the content of 1-alkene
Separation according tolenght and content ofthe short chainbranching
Separation of ethylene-1-hexene copolymers
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Analysis of EP rubbers and EPDM
R. Chitta, T. Macko, R. Brüll, G. Van Doremaele, L.C. Heinz, J. Polym. Sci., Polym. Chem., 2011, 49, 1840.
� EP-rubbers can be separated according to ethylene content and microstructure.
� The distribution of the diene in EPDM can be analyzed.
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HT 2D-LC→ELSD of EP rubbers
HPLC: Hypercarb™, 1-decanol → TCB, 0.1 mL/min, 140 °C
SEC: PL Rapide™ H, TCB, 2.5 mL/min, 160 °C
A. Ginzburg, T. Macko, V. Dolle, R. Brüll, Eur. Polym. J., 2011, 47, 319-329.
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Contour plot for EP copolymer
� Only the polymer peaks are selected and plotted as a contour plot.
� Contour plot for EP copolymer (59.7 wt. % ethylene)
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Calibrations: SEC, LAC and response of IR-detector
� The calibrations were used to recalculate the axes of the contourplots and the IR response and to obtain molar mass, chemicalcomposition and mass of polymer.
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Matrix approach for Fingerprinting
� Contour plots can be converted to matrices
� Matrix EP39.8 was subtracted from Matrix EP59.7.
S.S. Bhati, T. Macko, R. Brüll, Polyolefins J, 3, 2016, 119.
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Quantifying unique Segments in two Copolymers
� Subtraction of Matrix EP59.7 – Matrix EP39.8 was used to create the three dimensional surface plots showing unique segments in both the copolymers and their MMD as well as CCD.
� Differences in two samples can be quantified with the data from matrices.
� 89.5 wt. % unique segments
BR4
Folie 24
BR4 these are too many plots.Brüll, Robert; 09.09.2016
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Oligomer Separation – Peak Assignment
� Oligomers from C54 to C114 identified in PE 1 kg/mol. HypercarbTM/Decane→ODCB/ 130 °C
© Fraunhofer LBF
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PnBA-g-PS: 2D LC
� Contour plots obtained from a 2D-LC separation of a sample containing PnBA-g-PS copolymers and PS homopolymer using RI and UV detection.
� Fraction of homo-PS (ca. 14 kDa) present as byproduct
Tim
e [
min
]Molar mass [g/mol]
Hypercarb, THF�DCB 30 °C
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Steps for LC → NMR, FTIR and UV/RI (off-line)
Sample LC-ELSD
Replace ELSD by portable automatic fraction collector
Automatic fraction collectorTemperature range 25 – 200 °C
From LC
Sample holder Evaporator with vacuum pump
Transfer to NMR tube
NMR
After evaporation of solvents
9.0 9.5 10.0 10.5 11.0
0.0
0.1
0.2
0.3
0.4
432
EPDM 05090a
C2-61.5 mol %,
C3-36.5 mol %,
ENB-1.8 mol %,
VNB.0.29 mol %
EL
SD
sig
nal [V
]
Elution volume [mL]
1
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Preparative LC
15 16 17 18 19 20 21 22 230.0
0.2
0.4
0.6
0.8
1.0
8 % overlap
32
EL
SD
re
sp
on
se
[V
]
(Are
a n
orm
ali
ze
d)
SEC elution volume [mL]
1
7 % overlap
a)14 15 16 17 18 19 20 21 22 23
0.0
0.2
0.4
0.6
0.8
1.0
1.2
13 % overlap
16 % overlap
12 % overlap
2 543EL
SD
res
po
ns
e [
V]
(Are
a n
orm
alize
d)
SEC elution volume [mL]
1
15 % overlap
b)
3 fractions 5 fractions
8 fractions
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Multiple Injections – towards preparative 2D LC
� Multiple injections increase signal intensity
� No shift in spot position
� Significant quantities can be separated in one shot
1 x 20 x
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Summary
� Graphite as stationary phase allows to separate polyolefins according tocomposition and microstructure.
� Two-dimensional high temperature liquid chromatography withquantitative detection (HT 2D-LC-IR) enables to analyze bivariatedistributions (MMD and CCD).
� Matrix approach enables to quantify the unique and the identicalsegments at comparison of MMD and CCD of different EP copolymers.
� Automatic fraction collector in combination with HT-SEC or HT-LAC / NMR (off-line) can be applied for identification of the chemical compositiondistribution of polymers.
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Santa
Rosa
27/9
/2017
Group Material Analytics
Dr. K.N. Prabhu Dr. S.S. Bhati Dr. S. Damodaran Dr. A. Sanoria Dr. Dib Mekap Dr. Anton Ginzburg(SABIC) (BRASKEM) (TOSOH) (P & G) (Dow) (SABIC)
Dr. J.-H. Arndt N. Apel G.P. Horchler H. Mertyn Dr. F. Malz Dr. Rajesh Chitta (SABIC)
Dr. T. Macko Dr. G. Geertz Dr. B. Barton David Kot