COMPREHENSIVE MOLECULAR CHARACTERIZATION OF COMPLEX POLYMER SYSTEMS BY

COMPREHENSIVE MOLECULAR CHARACTERIZATION OF COMPLEX POLYMER SYSTEMS BY COUPLED METHODS OF LIQUID CHROMATOGRAPHY Dušan BEREK Polymer Institute of the Slovak Academy of Sciences, 84541 Bratislava, Slovakia, <dusan. berek@savba. sk> HPLC CONGRESS LONDON 2016 1

UTILITY PROPERTIES OF SYNTHETIC POLYMERS DEPEND ON MOLECULAR CHARACTERISTICS OF MACROMOLECULES MUTUAL ARRANGEMENT OF MACROMOLECULES PRESENCE OF ADDITIVES 2

MOLECULAR CHARACTERISTICS OF SYNTHETIC POLYMERS MOLAR MASS CHEMICAL STRUCTURE (COMPOSITION, FUNCTIONALITY, . . . ) PHYSICAL ARCHITECTURE (LINEAR, BRANCHED, CYCLIC, …, STEREOREGULAR, CIS- TRANS, …, ) 3

ALL MOLECULAR CHARACTERISTICS OF SYNTHETIC POLYMERS EXHIBIT DISPERSITY (DISTRIBUTION) A SYNTHETIC POLYMER MAY BE COMPOSED OF MILLIONS OF DISTINCT KINDS OF MACROMOLECULES HPLC CONGRESS LONDON 2016 4

IF MORE THAN ONE DISPERSITY IS PRESENT (MOLAR MASS DISPERSITY IS ALWAYS PRESENT !!) COMPLEX POLYMER BLENDS OF MACROMOLECULES WITH DISTINCT CHEMICAL STRUCTURE OR PHYSICAL ARCHITECTURE COMPLEX POLYMER SYSTEM 5

n SURPRISINGLY LITTLE ATTENTION IS PAID IN MANY RESEARCH LABORATORIES TO MOLECULAR CHARACTERISTICS OF POLYMERS USED IN THEIR STUDIES TO EXACT MOLECULAR CHARACTERIZATION OF PRODUCTS OF THEIR SYNTHESES AND TRANSFORMATIONS HPLC CONGRESS LONDON 2016 6

TO CHARACTERIZE A SYNTHETIC POLYMER ON MOLECULAR LEVEL THE MATERIAL IS TO BE SEPARATED A CHALLENGING TASK… LIQUID CHROMATOGRAPHY (MASS SPECTROMETRY) 7 …. HPLC CONGRESS LONDON 2016

THE MOST COMMONLY EMPLOYED POLYMER HPLC METHOD: SIZE EXCLUSION/ /GEL PERMEATION CHROMATOGRAPHY: SEC/GPC HPLC CONGRESS LONDON 2016 8

BOTH SEC/GPC SEPARATION SELECTIVITY AND DETECTOR SENSITIVITY ARE LOW IN PRINCIPLE SEC/GPC CANNOT GIVE QUANTITIVE DATA ON MOLAR MASS OF COMPLEX POLYMERS AND COMPLEX POLYMER SYSTEMS 9

LIQUID CHROMATOGRAPHY OF SYNTHETIC POLYMERS - RETENTION MECHANISMS FORMALLY, ONE CAN SPEAK ABOUT ENTHALPIC AND ENTROPIC CONTRIBUTION TO RETENTION VOLUME. 10

SIZE EXCLUSION CHROMATOGRAPHY - SEC/GPC THE SPECIAL CASE: Ú S 0, H ~ 0 DETERMINATION OF MOLAR MASS AVERAGES AND DISTRIBUTIONS (EXACT ALMOST EXCLUSIVELY FOR LINEAR HOMOPOLYMERS); LONG CHAIN BRANCHING; LIMITING VISCOSITY NUMBERS; RADII OF GYRATION; PREFERENTIAL SOLVATION IN MIXED SOLVENTS AND ASSOCIATION AND AGGREGATION OF MACROMOLECULES … HPLC CONGRESS LONDON 2016 11

SEC/GPC IS A VERY USEFUL METHOD WHICH IS HOWEVER OFTEN USED IMPROPERLY AND ITS RESULTS ARE SOMETIMES MISINTERPRETED, EVEN MISUSED… “SIZE EXCLUSION CHROMATOGRAPHY – A BLESSING AND A CURSE OF SCIENCE AND TECHNOLOGY OF SYNTHETIC POLYMERS” J. Sep. Sci. 2010, 33, 315 -335 12

MOREOVERSEC/GPC DISCRIMINATES MACROMOLECULES ACCORDING TO THEIR SIZE IN SOLUTION WHICH SIMULTANEOUSLY DEPEND ON ALL MOLECULAR CHARACTERISTICS SEC/GPC CANNOT DISCRIMINATE MACROMOLECULES WITH SIMILAR SIZES IN SOLUTION – 13

BOTH SEC/GPC SEPARATION SELECTIVITY AND DETECTOR SENSITIVITY ARE LOW SEC/GPC ONLY EXCEPTIONALLY ENABLES MONITORING MINOR MACROMOLECULAR CONSTITUENTS (>10%) MULTICOMPONENT COMPLEX POLYMER SYSTEMS AND THEIR CHARACTERIZATION HPLC CONGRESS LONDON 2016 14

AS A RESULT n APPLICABILITY OF SEC TO COMPLEX POLYMER SYSTEMS IS VERY LIMITED ENTHALPIC EFFECTS (INTERACTIONS) MUST BE ADDED TO THE ENTROPY CONTROLLED PARTITION RETENTION MECHANISM COUPLED METHODS OF POLYMER HPLC 15

ENTHALPIC INTERACTIONS IN POLYMER HPLC H ≠ 0; S ≠ 0 POLYMER – PACKING POLYMER – SOLVENT PACKING – ELUENT 16

ENTROPY AND ENTHALPY CONTRIBUTIONS TO RETENTION VOLUME OF MACROMOLECULES entropy-enthalpy compensation – CRITICAL CONDITIONS log M Mexcl enthalpy dominates but changes in IDEAL SEC/GPC are enormous LAC entropy controls retention, enthalpy contribution should be zero V 0 VM VR

KNOWN COUPLED METHODS OF POLYMER HPLC LIQUID CHROMATOGRAPHY UNDER CRITICAL CONDITIONS – LC CC (Skt. Petersburg, 1976) 1976 ELUENT GRADIENT POLYMER HPLC – EG LC (Skt. Petersburg, 1969; Kyoto, 1969; Tokyo, 1979) TEMPERATURE GRADIENT INTERACTION LIQUID CHROMATOGRAPHY - TGIC (Pohang, 1996) 18

LC CC MUTUAL COMPENSATION OF ENTROPY AND ENHALPY CONTRIBUTION TO RETENTION OF POLYMER MOLECULES MACROMOLECULES ARE COLUMN “INVISIBLE”. THEIR MOLAR MASS DOES NOT PLAY ANY ROLE! 19

LC CC SEPARATION OF BLOCK- AND GRAFTCOPOLYMERS, CYCLIC POLYMERS, TWO-COMPONENT POLYMER BLENDS, OLIGOMERS ACCORDING TO THEIR FUNCTIONALITY DRAWBACKS OF LC CC PEAK BROADENING, SENSITIVITY TOWARD (SMALL) TEMPERATURE AND ELUENT COMPOSITION VARIATIONS, LIMITED SAMPLE RECOVERY 20

EG LC called also GPEC elution promoting liquid eluent composition retention promoting liquid A, B – polymers with different enthalpic interactivities Each peak contains macromolecules with different molar masses 21

EG LC MOLAR MASS INDEPENDENT RETENTION; SEPARATION ACCORDING TO COMPOSITION AND BLOCKINESS OF COPOLYMERS; PEAK FOCUSING; HIGH SAMPLE CAPACITY; SHORT COLUMNS ARE SUFFICIENT; PROBLEMS: ELUENT GRADIENT INSTABILITY – REDUCED REPEATABILITY AND REPRODUCIBILITY LIMITED SAMPLE RECOVERY 22

TGIC SEPARATES MACROMOLECULES ACCORDING TO THEIR MOLAR MASS CHEMICAL STRUCTURE AND PHYSICAL ARCHITECTURE OF MACROMOLECULES BOTH ALSO AFFECT RETENTION SAMPLE RECOVERY = ? 23

NOVEL APPROACH - BARRIER METHODS LIQUID CHROMATOGRAPHY UNDER LIMITING CONDITIONS, LC LC (Bratislava, 1995) FAST PROGRESSION OF MACROMOLECULES DUE TO THEIR PORE EXCLUSION LOW VELOCITY OF PORE PERMEATING MOLECULES OF SOLVENTS. THE LATTER CAN PROMOTE ADSORPTION, ENTHALPIC PARTITION OR PRECIPITATION OF POLYMER. 24

IF ELUTED IN FRONT OF POLYMER SAMPLE, THE INTERACTION PROMOTING SMALL MOLECULES MAY CREATE SLOWLY ELUTING „BARRIER“, IMPERMEABLE FOR MACROMOLECULES. 25

BARRIER AND SAMPLE INTRODUCTION IN LC UNDER LIMITING CONDITIONS OF: DESORPTION = LC LCD; UNPARTITION = LC LCU; AND INSOLUBILITY = LC LCI P barrier BL SL W S C W TWO COMMON SIX-PORT TWO-WAY INJECTION VALVES ARE APPLIED, EQUIPPED WITH LOOPS OF APPROPRIATE SIZE. THE VALVES ARE OPERATED INDEPENDENTLY. BARRIER LOOP IS USUALLY LARGER THAN SAMPLE LOOP. 26

Sample composed of a retained and- a non-retained polymer adsorli barrier vi t 0 Liquid Chromatography under Limiting Conditions of Desorption Narrow pore column packings with large pore volume are preferred Mobile phase promotes sample elution t Eluent promotes elution of sample. Zone of barrier adsorli must be enough efficient to decelerate progression of one sample component due to its adsorption while another sample component is not adsorbed and therefore not retained by the zone. Volume of barrier is optimized by independent experiments. It should be neither too small nor too large. Sample volume vi can be extremely large, it may reach 20 % of column volume! 27

vi t 0 t 1 peak position in time t t 3 Barrier is subject to normal broadening, its peak is nearly Gaussian (red color). Non-adsorbed and therefore non-retained sample constituent (green) beak-through barrier and elutes in SEC mode. Adsorbed (blue) sample constituent is decelerated by barrier. It is accumulated on the barrier edge. Initially large volume of diluted sample is re-concentrated and narrow, focused 28 peak is formed.

BARRIER ACTION IN COMPLEX POLYMER SYSTEMS THAT CONTAIN MINOR CONSTITUENT(S) NARROW BARRIER OF ADSORLI EFFICIENTLY DECELERATES MINOR CONSTITUENT (ADSORBING POLYMER) FROM LARGE AMOUNT OF NON-ADSORBED POLYMER MATRIX, AND ALSO EXCESS OF POLYMER MATRIX WHILE MINOR CONSTITUENTS ELUTE NON-AFFECTED THESE FEATURES CAN BE EMPLOYED IN SEPARATIONS OF COMPLEX, MULTICOMPONENT POLYMER SYSTEMS CREATED IN THE COURSE OF POLYREACTIONS; FOR EXAMPLE PARENT HOMOPOLYMERS FROM BLOCK COPOLYMERS AND POSSIBLY ALSO HOMOPOLYMERS FROM STATISTICAL COPOLYMERS 29

LC LCD SEPARATION OF P 2 VP FROM P 4 VP

LC LCD separation of broad PMMA 294 (1%) and broad PVAC 320 (0. 5%) from broad PS 270 matrix (molar masses in kg. mol-1) n n n n Column bare silica gel 60 A Eluent THF/toluene 70/30 Two barriers of 1 m. L: #1 neat toluene, #2 THF/toluene 30/70 Time delay 0 -2 -3 (a) and 0 -3 -4 (b) min. Two barriers with different compositions were applied. First of them blocked PMMA the second one let through PMMA but blocked PVAC. PS eluted non-hindered. VR of polymers eluted behind barrier can be adjusted by changing time of barrier injection Eur. Polym. J. 45 (2009) 1798

* LC LCD SEPARATION OF FOUR-COMPONENT POLYMER BLEND OF PS+PMMA+PEO+P 2 VP Kromasil 60 Eluent DMF+THF+toluene B#1 – toluene B#2 – THF B#3 – Effect of time delay in injecting B#2 on VR of PEO 32

LC LCD OF BLOCK COPOLYMERS: SEPARATION OF PARENT HOMOPOLYMERS – A SCHEME Macromol. Chem. Phys, 209 2008, pp. 695 – 706 and 2213 - 2222 Polymer 51, 2010, pp. 587 – 596; J. Sep. Sci. 33, 2010, pp. 2476 – 3493

LC LCD separation of PS-b-PMMA copolymer containing parent homopolymers PS and PMMA. Identification of peaks by spiking experimens

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LC LCD SEPARATION OF PARENT HOMPOLYMERS FROM BLOCK COPOLYMER PMMA-b-Pt. BA

LC LCD SEPARATION OF PARENT HOMPOLYMERS FROM BLOCK COPOLYMER PMMA-b-Pn. BA

LC LCD SEPARATION OF PARENT HOMPOLYMERS FROM BLOCK COPOLYMER P 4 VP-b-Pn. BA

GENERAL STRATEGY FOR LC SEPARATION AND COMPREHENSIVE MOLECULAR CHARACTERIZATION OF COMPLEX POLYMER SYSTEMS TWO-DIMENSIONAL POLYMER HPLC (Toronto 1981, Berlin 1990) 39

TWO DIFFERENT LC SYSTEMS: FIRST LC COLUMN SEPARATES COMPLEX POLYMER OR COMPLEX POLYMER SYSTEM MAINLY OR EXCLUSIVELY ACCORDING TO CHEMICAL COMPOSITION OR ARCHITECTURE SECOND LC COLUMN IS SEC/GPC: IT DETERMINES MOLAR MASS AVERAGE AND DISPERSITY 40

TWO-DIMENSIONAL POLYMER HPLC P = PUMP; I = INJECTOR; C = COLUMN; D = DETECTOR OR SYSTEM OF DETECTORS; W = WASTE 41

Typical example of the two-dimensional separation of polymer blend: LC CC x SEC 42

ONLINE SAMPLE TRANSFER IN 2 D-LC GENERAL PROBLEM : BROAD PEAKS FROM THE 1 -D COLUMN ARE SPLIT INTO NARROW FRACTIONS, THESE ARE SUCCESSIVELY INTRODUCED INTO THE 2 -D COLUMN ELUTION RATE IN 1 -D COLUMN MUST BE LOW, WHILE ELUTION RATE IN 2 -D COLUMN IS TO BE (VERY) HIGH. SOLUTION: SEQUENCED TWO-DIMENSIONAL POLYMER HPLC ---- LC LC x SEC/GPC 43

SEQUENCED TWO-DIMENSIONAL LIQUID CHROMATOGRAPHY S 2 D LC, LCD x SEC/GPC (Bratislava 2010) LC LC - WITH ADVANTAGE LC LCD DISCRIMINATES DISTINCT CONSTITUENTS OF COMPLEX POLYMER SYSTEMS INTO NARROW INDIVIDUAL PEAKS 44

S 2 D LC THE FRACTIONS THUS GENERATED ARE IN THEIR ENTIRETY (IN FORM OF DEFINED SEQUENCES) SUCCESSIVELY TRANSPORTED INTO ON-LINE SEC/GPC COLUMN Macromolecules 43, 2010, pp. 9627 - 9634 45

Two-dimensional liquid chromatography LC LCD x SEC. Experimental arrangement for measurements. 46

COMPREHENSIVE MOLECULAR CHARACTERIZATION OF DIBLOCK COPOLYMER PS-B-PMMA THAT CONTAINS BOTH PARENT HOMOPOLYMERS BY S 2 D-LC 47

Good luck in comprehensive molecular characterization of synthetic polymers by liquid chromatography Thanks to: T. Macko, M. Jančo, M. Petro, M. Šnauko, J. Tarbajovská, E. Macová, A. Šišková 48