Characterization of complex polymer systems by MALDI Mass - PowerPoint PPT Presentation

Characterization of complex polymer systems by MALDI Mass Spectrometry” Concetto Puglisi National Research Council Institute of Polymers, Composites and Biomaterials Catania, Italy

Mass Spectrometry Analytical Techniques based on the production of ions in the high vacuum of the MS source, separation as a function of mass to charge ratio (m/z) and detection. Ions Ions Ions Separation Production Detection Ion Detectors Before ¡MALDI, ¡ ¡MS ¡ ¡analysis ¡of ¡polymers ¡was ¡restricted ¡to ¡addi:ves ¡or ¡low ¡ molecular ¡mass ¡products ¡obtained ¡from ¡pyrolisis ¡or ¡other ¡ ¡degrada:on ¡ methods. ¡ ¡(DP-­‑MS, ¡PY ¡GC/MS, ¡FAB/MS). ¡

Chemistry Nobel Prize 2001 John B. Fenn Koichi Tanaka R.Abate, ¡A. ¡Ballistreri, ¡G. ¡Montaudo, ¡D. ¡Garozzo, ¡G. ¡Impallomeni, ¡G. ¡Critchley , ¡ ¡K. ¡Tanaka , ¡ ¡ Rapid ¡Communica>on ¡in ¡ ¡Mass ¡Spectrometry, ¡vol. ¡7, ¡1033-­‑1036 ¡(1993) ¡

Matrix Assisted Laser Desorption Ionization (MALDI) MALDI/TOF ¡HAS ¡ALLOWED ¡THE ¡MASS ¡JUMP. ¡ A ¡REVOLUTION ¡IN ¡THE ¡ANALYTICAL ¡CHEMISTRY ¡OF ¡MACROMOLECULES. ¡ Ions Ions Ions Separation Production Detection MALDI TIME ¡OF ¡FLIGHT ¡(TOF) ¡ Ion Detectors WI WITH H MALD LDI MACROM OMOLE OLECULE ULES ARE DESOR ORBED INT NTACT

Matrix Assisted Laser Desorption Ionization (MALDI) The MALDI process consists of the intimate mixing of the sample with a high molar excess (up to 10 4 fold) of a low molecular mass organic matrix compound; Conversion of this mixture to a solid deposit; Introduction to a high vacuum chamber; Bombardment with a pulsed UV laser light; and Collection and measurement of the ions desorbed by the laser. Separation and identification of the ions produced by a Time Of Flight (TOF) tube

Each laser pulse generates a plume of particles, including ions and neutrals, matrix and analyte, which expand at supersonic speed from the surface of the probe and particularly at right angles to the surface. The ionization of polymer occurs by the formation of adducts ions with H + or with alcaline ions (litium, sodium or potassium) even they are not added to the solution

Modern Mass Spectrometry in Polymer Chemistry Most ¡Used ¡MALDI ¡Matrices ¡ Malononitrile DHB HABA CHCA Ditranolo IAA DEA-CHCA The triple role of the matrix is to incorporate and isolate the analyte molecules, absorb and transfer the laser energy to form the microplasma, and finally, assisting in the formation of the macromolecular ions.

MALD LDI-T -TOF OF OF OF POL OLYMERS Main ain FE FEATUR URES Detection of Intact Molecules Ø Very High Sensitivity Ø High Resolution (> 20000 ppm) Ø Main ain APPLI LICATIONS ONS Molar Mass Determination q Copolymer Analysis q End Groups Determination/Structure q v Mechanisms of Polymer Degradation v Mechanisms of Synthesis

MALD LDI-T -TOF OF OF OF POL OLYMERS Main ain FE FEATUR URES Detection of Intact Molecules Ø Very High Sensitivity Ø High Resolution Ø Main ain APPLI LICATIONS ONS Molar Mass Determination q Copolymer Analysis q End Groups Determination q v Mechanisms of Polymer Degradation v Mechanisms of Synthesis

Polystyrene, Narrow Distribution Mw 330,000; 600,000; 900,000

Pol olystyrene ene (D=1.001) 1.001) Ver ery Nar Narrow Dis istribut ibution ion 200 ¡ 180 ¡ M + 156970 ¡ 160 ¡ Osmometry Mn= 153600 Viscosometry Mv=159770 140 ¡ Light Scattering Mw=158180 counts/1000 ¡ 120 ¡ M ++ GPC (SEC) Mn= 152350 Mw= 156050 100 ¡ 79160 ¡ , ¡ MALDI Mn = 152350 80 ¡ Mw= 156450 60 ¡ 40 ¡ 2M + 312530 ¡ 20 ¡ 0 ¡ m/z ¡

O O D 9 CH 3 CH 3 CH 3 A= CH 3 O C O CH 3 O C O n CH 3 CH 3 CH 3 1800 O CH 3 CH 3 B= H O CH 3 O C O n D 12 CH 3 CH 3 1600 A 17 O CH 3 CH 3 A 14 C= H O O C O OH A 21 n 1400 CH 3 CH 3 D 15 O CH 3 A 25 O O O C D= 1200 n CH 3 s D 8 t 1000 n u A 16 D 14 o A 14 C D 15 A 15 A 13 D 17 D 16 800 A 33 C 14 C 16 600 B 17 B 16 B 15 B 14 400 A 42 200 4000 4500 A 50 m/z 0 2000 4000 6000 8000 10000 12000 14000 16000 18000 m/z Bisphenol ¡A ¡Polycarbonate, ¡Mw ¡50.000 ¡by ¡SEC ¡

Coupling «off-line» SEC with MALDI MALDI as absolute mass detector for GPC 49000 190000 m/z m/z A.U 310000 2400 m/z m/z 0 10 20 30 40 Vr ¡(ml)

5.5 5.5 Mw PMMA standards by MALDI Mw PMMA standards by MALDI Mw PMMA Standards by Supplier Mw PMMA Standards by Supplier 5.0 5.0 Mw of PMMA Fractions by MALDI Mw of PMMA Fractions by MALDI log(Mw) log(Mw) 4.5 4.5 4.0 4.0 3.5 3.5 20 20 21 21 22 22 23 23 24 24 25 25 26 26 27 27 28 28 29 29 30 30 31 31 Ve (mL) Ve (mL)

Determinazione di pesi molecolari assoluti ULTEM 1000 80 70 Volume di eluizione e Mw di ciascuna 60 s frazione analizzata mediante MALDI t i n 50 U Ve (mL) Mw Log Mw y 40 r a r 30 t i b r 20 A 28.8 52500 4.72016 10 29.03 49150 4.69152 0 29.5 40500 4.60745 0 10 20 30 40 50 29.74 5700 4.55267 Ve(ml) 30.44 26900 4.42975 31.38 19000 4.27875 4.8 32.08 14000 4.14613 4.6 33 10250 4.01072 2 Y ¡= ¡13.99 ¡-­‑ ¡0.4498X ¡+ ¡0.004456X 4.4 33.254 8950 3.95182 4.2 33.72 7920 3.89873 log ¡Mw 34.43 6620 3.82086 4.0 35.56 3780 3.57634 3.8 36.77 2970 3.47276 3.6 37.7 2360 3.37291 3.4 38.64 1890 3.27646 3.2 28 29 30 31 32 33 34 35 36 37 38 39 Ve(mL)

Polycarbonate 100 5.2 5.0 PC 4.8 4.6 s t 4.4 i n w u 50 M y 4.2 r a g r o t i l 4.0 b r a 3.8 3.6 3.4 0 3.2 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 Ve (mL) TABLE 1 Molar Mass Distribution of PC calculated from SEC curves obtanined at different concentrations (wt%). SEC/MALDI Polystyrene a M n a M p a b M n b M p b Conc. Solvent M w M w 0.3 CHCl 3 22200 10300 22400 55800 23600 58400 0.5 CHCl 3 22000 10200 21900 55600 23400 56700 1 CHCl 3 18350 10250 18500 50150 21850 22400 2 CHCl 3 17500 9700 17000 46100 20000 42100

MALD LDI-T -TOF OF OF OF POL OLYMERS FEATUR FE URES Detection of Intact Molecules Ø Very High Sensitivity Ø High Resolution Ø APPLI LICATIONS ONS Molar Mass Determination q Copolymer Analysis q End Groups Determination q v Mechanisms of Polymer Degradation v Mechanisms of Synthesis

Copolymers microstructure § Copolymer Composition § Average sequence length § Degree of randomness § The weight fraction of copolymers with respect to homopolymers Structure Characterization of Copolymers NMR ( 1 H – 13 C) MALDI Mass Spectrometry

MODELING PROCESS BASED ON CHAIN STATISTICS 1. CHOICE OF DISTRIBUTION MODELS A NUMBER OF DIFFERENT DISTRIBUTION MODELS CAN BE CONSIDERED, OLIGOMERS ABUNDANCES CAN BE GENERATED ACCORDING TO EACH MODEL (BERNOULLIAN, MARKOFFIAN 1° AND 2°, SEQUENTIAL) 2 THEORETICAL NMR OR MASS SPECTRA GENERATE THEORICAL NMR OR MASS SPECTRA FOR A SPECIFIC COPOLYMER SEQUENCE BY ASSUMING PEAKS INTENSITIES EQUAL TO RELATIVE OLIGOMER ABUNDANCES, AND APPLYING THE APPROPRIATE CONVOLUTION AND MULTIPLICITY RULES I AmBn = f(P AA , P AB , P BA , P BB ) 3 ITERATION AND BEST FIT MINIMIZATION A SERIES OF THEORETICAL MASS SPECTRA ARE ORIGINATED AND, COMPARING THE EXPERIMENTAL MS INTENSITIES WITH THOSE CALCULATED FOR A SPECIFIC MODEL, THE MOST LIKELY COPOLYMER MICROSTRUCTURE AND COMPOSITION CAN BE DETERMINED AF = q Σ i (I i exp - I i calcd ) 2

Number of MS peaks (n+1) random AB copolymer (1:1) A2B2 A3B2 A2B3 AB ) . u A2B A3B AB3 AB2 . b r a ( . s A4B AB4 n e t B2 A2 n i A3 B3 A4 B4 A5 B5 300 400 500 600 700 800 900 1000 1100 m/z

Composition for a AB copolymer (Composition Estimates Method) Oligomers Oligomer For ormula mula Monomers C 1 A I(A) / { I(A) + I(B) } Dimers C 2 A {2I(A 2 ) + I(AB)} / {2I(A 2 ) + 2I(AB) + 2I(B 2 )} Trimers C 3 A {3I(A 3 ) + 2I(A 2 B) + I(AB 2 )} / {3I(A 3 ) + 3I(A 2 B) + 3I(AB 2 ) + 3I(B 3 )} Tetramers C 4 A {4I(A 4 ) + 3I(A 3 B) + 2I(A 2 B 2 ) + I(AB 3 )}/ {4I(A 4 ) + 4I(A 3 B) + 4I(A 2 B 2 ) + 4I(AB 3 ) 4I(B 4 )}

Number Number of of peaks peaks expect xpected ed for or two, , thr hree ee ad ad four our components copol component copolymer mers ABC ABCD Oligomers AB 2-mers 3 6 10 3-mers 4 10 20 4-mers 5 15 35 5-mers 6 21 56 6-mers 7 28 84 7-mers 8 36 120 8-mers 9 45 165 9-mers 10 55 220 10-mer 11 66 286 11 - mers 12 78 364 12 - mers 13 91 455 13 - mers 14 105 560 14 - mers 15 120 680 15 - mers 16 136 816 16 - mers 17 153 969

A 5 B 6 1000 A 6 B 6 A 6 B 5 A 6 B 7 A 6 B 6 A 6 B 5 A 5 B 6 a.i. A 7 B 5 A 5 B 7 A 4 B 7 A 8 B 5 A 7 B 4 A 7 B 7 A 8 B 7 A 4 B 8 800 A 8 B 4 A 10 B 3 A 3 B 7 A 5 B 5 A 7 B 8 A 9 B 3 A 2 B 9 A 9 B 4 A 3 B 8 A 2 B 8 A 8 B 3 A 3 B 9 A 8 B 8 A 8 B 9 600 A 9 B 9 2600 2700 2800 2900 3000 3100 A 9 B 10 m/z A 10 B 10 400 A 10 B 11 A 11 B 11 200 0 2000 3000 4000 5000 6000 7000 8000 9000 m/z MALDI-TOF spectrum of butylene adipate (A)/sebacate (B) copolymer.