© 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)

© Fraunhofer LBF

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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

© Fraunhofer LBF

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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

© Fraunhofer LBF

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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.

© Fraunhofer LBF

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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.

© Fraunhofer LBF

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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

© Fraunhofer LBF

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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

© Fraunhofer LBF

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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

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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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© Fraunhofer LBF

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Santa

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/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