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Analytical strategy for the microstructural characterization of MAA-MMA copolymers

Analytical strategy for the microstructural characterization of MAA-MMA copolymers. Rémi Giordanengo , (1) Stéphane Viel, (1) Manuel Hidalgo, (2) Béatrice Allard-Breton, (2) André Thévand (1) and Laurence Charles (1). (1) Aix-Marseille University – Marseille, France

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Analytical strategy for the microstructural characterization of MAA-MMA copolymers

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  1. Analytical strategy for the microstructural characterization of MAA-MMA copolymers Rémi Giordanengo,(1) Stéphane Viel,(1) Manuel Hidalgo,(2) Béatrice Allard-Breton,(2) André Thévand (1) and Laurence Charles (1) (1) Aix-Marseille University – Marseille, France (2)ARKEMA – Centre de Recherche Rhônes-Alpes – Pierre-Bénite, France

  2. Copolymer Characterization Nature of end-groups X ,Y Nature of MAA-MMA copolymer block vs random MAA M = 86 Da MMA M = 100 Da Composition n , m MolecularWeight Mn , Mw 2

  3. ESI-MS ESI(+)-MS spectrum 613 2 distributions : [M + Na]+ [M + 16 + Na]+ 513 599 627 527 713 MMA MMA 699 ∆ m/z 100 ∆ m/z 100 499 727 MAA MAA ∆ m/z 86 ∆ m/z 86 3

  4. ESI-MS ESI(+)-MS spectrum 327 427 MX, MY unknown 413 613 313 513 599 627 713 527 699 n, m ? 499 685 727 4

  5. ESI-MS/MS MS/MS requested to determine the actual values of n and m Dissociation rules of MAA-MMA copolymers in negative and positive mode ESI : • water elimination Na+ Na+ Between two consecutive neutral MAA → MAA/MAA pair in the polymeric chain • methanol elimination Na+ Na+ Between neutral MAA and MMA→ MAA/MMA pair in the polymeric chain The number of water and methanol losses is monitored to reveal the number and arrangement of MAA and MMA units in the selected precursor ion Giordanengo, R. et al. Journal of the American Society for Mass Spectrometry 2009, 20 (1), 25-33 ; Giordanengo, R. et al.Rapid Communication in Mass Spectrometry2009, 23 (11) 1552-1567 ; Giordanengo, R. et al. AnalyticaChimicaActa2009, 654, 49-58

  6. ESI-MS/MS m/z 499 (2 ; m+1) - MeOH - H2O Neither water nor methanol losses in MS/MS spectra of precursor ion in the first column No MAA unit n = 0 Only one loss of water Only one MAA/MAA pair 2 MAA units Only one loss of methanol Only one MAA/MMA pair 1 MMA unit m+1 = 1 6

  7. ESI-MS/MS m/z 771 (4;2) m/z 753 m/z 735 1 loss of H2O 2 losses of MeOH 1 MAA-MAA pair 2 MAA-MMA pairs 2 MMA units 2 consecutivelosses of H2O 2 MAA-MAA pairs 4 MAA units m/z 771 m/z 739 m/z 721 Different dissociation routes from the same precursor ion Random nature of the studied MAA-MMA copolymer MX + MY = 204 Da - H2O m/z 707 m/z 689 - MeOH 7

  8. Limitations of the ESI-MS/MS approach Dissociation of MAA-MMA co-oligomer sodiated adducts allows : • To reach the co-monomeric composition of co-oligomers • To reveal the random nature of the studied MAA-MMA copolymer • To determine the sum of the end-group masses (MX + MY) However : • The lack of specific fragmentation does not allow the end-groups to be structurally characterized (contrary to what is usually obtained in the case of homopolymers such as PMMA) 8

  9. Other ESI-MS Limitations ESI-MS spectrum of the MAA-MMA copolymer : • Distribution parameters largely underestimated as compared to NMR data (Mn 3100 Da) • Same phenomenon in ESI of constitutive homopolymers PMMA and PMAA Signal only in the low m/z range indicating a strong bias toward low mass oligomers PMMA 1590 PMAA 1250 Mw (1+) 612 Mw (2+) 728 Mw (1+) 865 Mw (2+) 1592 Wrong values of Mn and Mw Uncorrect MAA/MMA ratio Strong bias toward low mass oligomers for all acrylic polymers 9

  10. Limitations in terms of Molecular Weight determination MALDI-MS : • In contrast, MALDI-MS spectra of constitutive homopolymers PMMA and PMAA are more realistic • However, no signal obtained in MALDI for the MAA-MMA copolymers PMMA 1590 PMAA 1250 10

  11. Strategy End-group characterization : • Need for a homopolymer to allow the structure of X and Y end-groups to be reached by means of ESI-MS/MS Molecular weight determination : • Need for a homopolymer to allow the distribution parameters to be obtained from MALDI-MS data 1 STRATEGY 2 Use of a methylation reaction to transform the MAA-MMA copolymers in PMMA homopolymers Experimental • ~ 50 mg of MAA-MMA copolymer in 20 mL of a MeOH/H2O mixture (19/1, v/v) • (stirred 2h at room temperature) • Addition of an excess of trimethylsilyldiazomethane(stirred 3h at room temperature) • Dryingat 30°C overnight 3 11 Couvreur, L.; Lefay, C.; Belleney, J.; Charleux, B.; Guerret, O.; Magnet, S. Macromolecules 2003, 36, 8260-826

  12. Strategy Derivatization of the copolymer for the distribution parameters 12

  13. Methylation of PMAA homopolymers MALDI(+)-MS spectrum methylated PMAA 1700 PMAA 1700 Methylation - A single PMMA distribution is obtained, indicating all acrylic acid functions of PMAA have been methylated. - Good signal-to-noise ratio is measured from low laser fluence (~ 40%). - Complex MS spectrum due to the ability of PMAA to bind numerous Na+ cations. - High laser fluence (65%). 13

  14. Methylation for MolecularWeightdetermination 800 No signal obtained before methylation 400 2000 3500 5000 1000 After methylation Intense MALDI-MS signal Mw can be determined by MALDI and PGSE NMR 600 200 4110 4870 2000 6000 4000 Giordanengo, R.; Viel, S.; Hidalgo, M.; Allard-Breton, B.; Thevand, A.; Charles, L. Journal of the American Society for Mass Spectrometry 2009, submitted 14

  15. Strategy Derivatization of the copolymer for the end-group characterization 15

  16. Methylation for end-group characterization ESI(+)-MS : methylated MAA-MMA MAA-MMA Methylation [M + Na]+ (MX + MY) = 204 [M + Na]+ (MX + MY) = 204 [M + 16 + Na]+ (MX + MY) = 220 [M + 16 + Na]+ (MX + MY) = 220 After methylation : • ESI-MS simplified • A single PMMA distribution is obtained indicating all MAA units have been methylated • No modification of the end-groups during the methylation reaction 16

  17. Methylation for end-group characterization ESI(+)-MS/MS of the methylated MAA-MMA copolymer : m/z 827 Dissociation rules of PMMA homopolymers in positive mode ESI (1) : C+ C+ C+ C+ C+ C+ C+ SeriesB SeriesF SeriesA SeriesD Jackson, A. T.; Yates, H. T.; Scrivens, J. H.; Critchley, G.; Brown, J.; Green, M. R.; Bateman, R. H. Rapid Communications in Mass Spectrometry 1996, 10, 1668 ; Jackson, A. T.; Yates, H. T.; Scrivens, J. H.; Green, M. R.; Bateman, R. H. Journal of the American Society for Mass Spectrometry 1997, 8, 1206 17

  18. Methylation for end-group characterization ESI(+)-MS/MS of the methylated MAA-MMA copolymer : Dissociation rules of PMMA homopolymers in positive mode ESI (2) : C+ C+ Series F Series E Series C Series D C+ C+ C+ C+ Jackson, A. T.; Yates, H. T.; Scrivens, J. H.; Critchley, G.; Brown, J.; Green, M. R.; Bateman, R. H. Rapid Communications in Mass Spectrometry 1996, 10, 1668 ; Jackson, A. T.; Yates, H. T.; Scrivens, J. H.; Green, M. R.; Bateman, R. H. Journal of the American Society for Mass Spectrometry 1997, 8, 1206 18

  19. Methylation for end-group characterization Application of the dissociation rules of PMMA homopolymers in positive mode ESI : m/z 827 Most intense fragment ions: Series A or B A0 A1 The two most intense fragment ions could be identified to Series A, revealing Y = H Na+ A0 : m/z 110 A1 : m/z 210 19

  20. Methylation for end-group characterization Application of the dissociation rules of PMMA homopolymers in positive mode ESI : m/z 827 Since Y = H, product ions D and E can be assigned A0 A1 Series D Series E Validation of the nature of Y MY = 1 Y = H Na+ Na+ E0 : m/z 209 E1 : m/z 309 E2 : m/z 409 E3 : m/z 509 E4 : m/z 609 D2 : m/z 265 D3 : m/z 365 D4 : m/z 465 D5 : m/z 565 20

  21. Methylation for end-group characterization Application of the dissociation rules of PMMA homopolymers in positive mode ESI : MX + MY = 204, with MY = 1 → MX = 203 Based on MX = 203, product ions B, C and F can be identified SeriesF SeriesB SeriesC Validation of MX = 203 Na+ Na+ Na+ F1 : m/z 381 F2 : m/z 481 F3 : m/z 581 B0 : m/z 226 B1 : m/z 326 C1 : m/z 425 C2 : m/z 525 C3 : m/z 625 C4 : m/z 725 21

  22. Methylation for end-group characterization Use of a sulfurated agent during the copolymer synthesis, 2-ethylhexyl thioglycolate (M = 204 Da) 2 additionnal product ions detected at m/z 715 et m/z 683 allow to validate the structure proposed for X Na+ Na+ 715 Proposed structure for X Na+ 683 22

  23. NMR analysis NMR 1D (1H, 13C) and 2D (COSY, HSQC, HMBC, DOSY) analysis Proposed structure of X : Validation of the structure of the end-groups 23

  24. Conclusion Methylation of MAA-MMA copolymer allow : • A complete microstructural characterization (validated by NMR anlysis) • The distribution parameters to be determined (with the help of NMR data) This derivatization strategy can be envisaged for any copolymer : • Not amenable to MALDI • Which can be transformed into a homopolymer 24

  25. Acknowledgments • The organisation committee • The French Society for Mass Spectrometry • The Spectropôle, analytical facility of Aix-Marseille University, for the special access to the instruments • ARKEMA, for the financial support • SACS and C&S members • Thank you for your attention 25

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