6.88%) as a white solid. ...... Figure 3, avec son spectre MS/MS et celui du .... peut être calculé à partir de l'ensemble des données mesurées sur un spectre MS.
MASS SPECTROMETRY of
SYNTHETIC POLYSILOXANES −
FROM LINEAR MODELS TO PLASMA-POLYMER NETWORKS
T. FOUQUET, L. CHARLES
“They did not know it was impossible, so they did it.” S.L. Clemens, aka M. Twain
To my family, To the four-count rhythm, To those who dare, and achieve greatly.
Aix-Marseille University - Institut de Chimie Radicalaire Spectrométries Appliquées à la Chimie Structurale France
Public Research Centre Henri Tudor Advanced Materials and Structures Luxembourg
Mass Spectrometry of
Synthetic Polysiloxanes From linear models to plasma-polymer networks
Thierry Fouquet, Centrale Marseille Engineer Under the supervision of Pr Laurence Charles
Thesis defense committee Pr C. WESDEMIOTIS Dr S. WEIDNER Pr T. BELMONTE Dr D. RUCH Pr S. HUMBEL Dr D. GIGMES Pr F. AUBRIET Pr L. CHARLES
The University of Akron, United States Federal Institute for Materials Research and Testing BAM, Germany Lorraine University, France Public Research Centre Henri Tudor, Luxembourg Aix-Marseille University, France CNRS - Aix-Marseille University, France Lorraine University, France Aix-Marseille University, France
Submitted October 2012, Revised January 2013
Supported by the Fonds National de la Recherche
(Reviewer) (Reviewer) (Examiner) (Examiner) (Examiner) (President) (Thesis co-Advisor) (Thesis Advisor)
Content This manuscript is formed of two separate books – a “Supporting Data Book” should be of great assistance for mass measurements, ab initio geometries and miscellaneous supplementary materials. Mentions will be given when data should be found in this Supporting Data Book, as “Supplementary Table/Figure/Scheme” or in the margin.
Acknowledgements
p. 9
Abbreviations & Acronyms
p. 11
Introduction
p. 13
Part I - Plasmas, Plasma-polymers & Polymers
p. 17
Chapter 1 - Plasmas and thin film deposition Chapter 2 - Plasma-polymerization mechanisms Chapter 3 - Conventional polymers and Mass Spectrometry Part II - Soluble plasma-polymers & Reference compounds Introduction – ppHMDSO samples Chapter 1 - First reference compounds: CH3-PDMS & H-PDMS Chapter 2 - Hydrides-containing poly(siloxane)s Chapter 3 - Cross-linked poly(siloxane)s: the POSS model Chapter 4 - Methoxy-terminated poly(siloxane)s Chapter 5 - ppD4: reducing the reactivity in plasma-polymerization Conclusion – ppHMDSO soluble parts & mass spectrometry Part III – Towards mass analysis of unsoluble plasma-polymers Introduction: controlled degradation of polymers Chapter 1 - Ethanolysis specificity Chapter 2 - Mass analysis of plasma-polymer unsoluble part
p. 19 p. 27 p. 33 p. 41 p. 43 p. 49 p. 77 p. 95 p. 111 p. 127 p. 145 p. 149 p. 151 p. 153 p. 171
Last few words – Insights into the plasma-polymerization process
p. 187
List of Publications
p. 195
English / French abstracts
p. 197
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Acknowledgements
F
irst, and foremost I guess, I would like to thank my family, my parents, my brother and my “missing” sister for their presence, support, love and their uninterrupted encouragements since the very beginning of this adventure. This work is also and mainly theirs and nothing would have been done without them staying beside me. The new and hauntingly beautiful generation is growing up, and this work is somehow dedicated to my dearest nieces and nephews I have fallen in love with. I thank my advisor and mentor, Pr. Laurence Charles, for these very special and incredibly rich years. I am, and I will be infinitely and profoundly grateful for her dedication. She is a remarkable teacher, introducing me to mass spectrometry and allied topics at the end of my engineering school, at a time I was facing an undefined and colorless future. She has been on my side throughout these past four years, and I thank her for this continuous support. These bright coming days full of millions of opportunities are obviously the fruits of her labor. Advisers from the CRP Henri Tudor – David Ruch, Valérie Toniazzo, Jérôme Bour and Marc Angotti - are also gratefully acknowledged, for their help, interesting conversations and contributions, and the last but not least, for the writing of the project which made me moving to Luxembourg, finding a lovely and welcoming place plenty of warm people. I obviously thank – in advance but I am sure they will not mind about it - all the people, professors and doctors, who will serve in my defense committee. In addition to those already mentioned, and in particular, Pr. Chrys Wesdemiotis I met several times at the ASMS, a leader in the field of mass spectrometry of polymers I will try to mimic, and Dr. Stefen Weidner I will by honored to meet on that defense day. Many thanks also to Pr. Thierry Belmonte who will bring his knowledge in plasmas to comment this work with another and precious point of view. I thank Pr. Stephane Humbel, for the patience he shew during the theoretical calculations days. No breakthrough has been made, but a funny journey in the very intimacy of matter, and I am proud we have been travelling together. I wish him the best of luck and happiness in his future. I would especially like to thank Caroline Mangotte-Barrère, Benoit Mangotte and Christophe Chendo for the numerous and tremendous moments we spent together, during the ASMS days and the following vacations, during the JFSM days, at lab and anywhere we have been together. Their presence was the greatest present they gave to me, and this work may never have been done without them. May the force be with you, and see you in other times, in other grounds. I also address a special thank to Valérie Monnier, as her blonde hair have been a pretty lighthouse in the research storm. I wish to express my thanks to all the lovely people I met at the CRP Henri Tudor, with whom I have shared experiences, discussions, lunches, coffee breaks and many other things related or not to my thesis (amongst those a few would be called immoral, depending on each morality): Joao A.S. Bomfim, Ludivine Fetzer, Frederic Addiego, Pierre Verge, Iulia Miai, Jean Luc Biagi, Doriane del Frari, Julien Bardon, Christele Vergne, Regis Vaudemont, Benoit Marcolini, Claude Becker, Stéphanie Etienne, Ivan Keranov, Marc Michel, Vincent Ball, Jean di Martino, Fatima Hassouna and all those I have forgotten here and to whom I express my regrets. Let me also thank more particularly the PhD students I met at the CRP: Fatima Eddoumy, Blandine Friedrich, Abdelhalim Zoukel, Nicolas Burger, Georgio Kfoury, José Alejandro Delgado-Rangel, Kui Wang, Kadir Apaydin, Gregory Mertz, Cédric Amorosi and Julien Petersen; the last four of them are acknowledged in a very dedicated way… I cannot be more precise here.
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Acknowledgements
I would also like to thank “separately” my “personal” technical and financial staff, Sabrina Morais, Christelle Vergnat, Frederic Faltot and Caroline Ruszkiewicz for their unlimited help and good mood. I acknowledge all the people from Aix-Marseille University, especially the SACS and Spectropole teams, with whom I enjoyed some funny moments throuhout the past several years: Fabio Ziarelli (thanks for the solid state NMR experiments too…), Aura Tintaru, Stéphane Viel, Rosy Rosas, … Best wishes also to the SACS PhD students I have been proud to know: Yannis and Mohamed Major, Rémi Giordanengo, … And a special mention to Aurélie Mizzi and Bruna Albergaria, crazy pretty and unforgettable ladies I have known in the very last days, whose smiles are frozen in time. The financial supports of the Fonds National de la Recherche (FNR) and of the Aix-Marseille University are also gratefully acknowledged. I thank Spectropole for the special access to instruments during these three years of thesis. All the scientific committees of all the conferences I have attended are also warmly thanked, for the opportunities to present talks and posters, as well as meeting fantastic, funny, interesting and sometimes unpleasing people. A special thank to Fabien Chainet who offered me the present I was waiting for a long time, using my research results in his own work… Many thanks to the American Society for Mass Spectrometry, and its French little sister, the French Society for Mass Spectrometry as well as its “Club Jeune” for the exciting moment I have lived. All these societies and people are parts of the research world and I have truly appreciated to be one of them, at least for a moment. I do not know yet if this time has gone, or if the show will go on. Thanks go to the Oxford Chemistry Primers and their forceful template I shamelessly copied. I am also grateful to Thermo Fischer Scientific and the International Journal of Mass Spectrometry for the “best student paper award” I won, and I humbly express a painful thought to Detlef Schröder, who presented me with the prize and left us as orphans a few months later. I should also be grateful to the people I met during my engineering school years, who pushed me towards the unknown and somber road to PhD – known worldwide as the road to perdition, at a time all my classmates were leaving for the US, China, Japan or Brazil to earn thousands of dollars. Do not panic, I have forgiven all of them. Poor, poor clogged capillaries, six feet under you are resting now, you will be in my thoughts forever. And finally, I would like to thank all the researchers and their beautiful works all around the world, regardless of their specialties, which make us dreaming about future successes and help us to fulfill our ambitions, day by day. All these above-mentioned people have made contributions in different ways, but equally precious and unforgettable.
And to all the others, best wishes…
Duly noted, on a rainy Monday as many others in Luxembourg, Thierry Fouquet
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Abbreviations & Acronyms All the abbreviations and acronyms used in this present work are defined below, listed in the alphabetical order for sake of simplicity. A brief definition is however proposed in the forthcoming text at the first appearance of each acronym.
AC/DC: Alternating Current / Direct Current (and a famous Australian rock band). AP: Atmospheric Pressure
Collision
Induced/Activated
CP: Cross-Polarization Da: Dalton (neutral mass unit) DBD: Dielectric Barrier Discharge DBE: Double Bond Equivalent DFT: Density Functional Density DME: Dimethylether (= methoxymethane) DMS: Dimethylsiloxy ESI: Electrospray Ionization FT-IR: Fourier Transform InfraRed Spectroscopy GC: Gas Chromatography Ha: Hartree * The Hartree (Ha) is the atomic unit of energy for which the 2006 recommended CODATA value is 4.35974394(22).10-18 J [a].
HF: Hartree-Fock HMDSO (in plasma community): Hexamethyldisiloxane (known as HMDS in the chemistry community, not to be confused with hexamethyldisilazane). Ip: Polydispersity index
LTE: Local Thermodynamic Equilibrium m: molar mass
ASAP: Atmospheric Solid Analysis Probe CID/CAD: Dissociation
ISD: In-Source Decay
(MA)LDI: (Matrix Assisted) Laser Desorption Ionization MAS: Magic Angle Spinning Mn: Number average molecular weight MS: Mass Spectrometry MS/MS: two-stage (tandem) Mass Spectrometry MS3: three-stage mass spectrometry Mw: Weight average molecular weight NMR: Nuclear Magnetic Resonance PDMS: Poly(dimethylsiloxane) POSS: Polyhedral oligomeric silsesquioxane pp: plasma-polymerized SEC: Size Exclusion Chromatography TGA: Thermo-gravimetric Analysis THF: Tetrahydrofuran TMDSO: Tetramethyldisiloxane TMS: Tetramethylsilane TOF: Time-of-Flight TS: Transition State XPS: X-ray photoelectron spectroscopy z: number of charges ZPC: Zero Point Correction
[a] P.J, Mohr, B.N. Taylor, D.B. Newell, Review of Modern Physics 2008, 80, 633.
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Introduction As defined by H. Biederman [1], the term “plasma-polymer” denotes a material that is created as a result of a passage of an organic gas or vapor through an electric discharge. It is usually deposited as a thin, poorly soluble and highly cross-linked film. Due to their unique properties arising from their particular network organization, plasma-polymers have a huge potential for industrial applications. In particular, organosilicon coatings formed from plasma-polymerization of hexamethyldisiloxane (HMDSO) were found to be good candidates for a wide range of applications such as gas barrier [2-4] and anticorrosion [5, 6] coatings. In addition, the possibility of synthesizing and depositing such materials by atmospheric pressure plasma processes allows the use of low cost equipments which can be extended to on-line processing at industrial scale. Among various techniques enabling atmospheric pressure non thermal plasmas, dielectric barrier discharges consist of generating discharges in the gas gap between two plane-parallel metal electrodes, one of them being covered with a dielectric layer [7] {Part I, Chapter 1}. The plasma polymerization process is usually considered as a mechanism involving free radicals generated during collisions of energetic electrons with organic molecules injected in the gas gap [1]. A general deposition mechanism for HMDSO precursor in atmospheric pressure plasma-polymerization was very recently proposed by Fanelli et al. [8-10], based on the knowledge of species detected in the exhaust gas and the chemical composition of the so-obtained plasmapolymers deposits {Part I, Chapter 2}. As a result, plasma-polymers are expected to be composed of short chains, randomly branched, and terminated with a high degree of cross-linking, that is, a much more complex structure than that of materials synthesized by conventional polymerization methods. Microstructural characterization of polymeric materials is the first step towards the understanding of their properties as well as a deeper knowledge of polymerization processes involved in their synthesis. Plasma polymers of HMDSO (ppHMDSO) were reported to consist of a mixture of both organic polydimethylsiloxane (PDMS) and inorganic (SiOx) silicabased species, as revealed by conventional techniques such as Fourier Transform InfraRed (FTIR) spectroscopy [11-14] and X-ray photoelectron spectroscopy (XPS) [11]. Solid-state nuclear magnetic resonance (NMR) devoted to 29Si remains however the reference technique to describe the chemical environment of silicium atoms. Although these techniques are of asset for determining the nature of functional groups present in the plasmapolymer film, they provide information on chemical composition rather than molecular structure. Actually, so far, no detailed study focused on structural characterization of plasma-polymers has ever been reported. This prompted us to undertake this thesis work, which aimed at defining an analytical strategy to get robust and accurate structural data on these materials.
[1] H. Biederman, Plasma Polymer Films, 2004, Imperial College Press, Covent Garden, UK. [2] Y. Leterrier, Progress in Materials Science 2003, 48, 1. [3] L. O’Neill, L.A. O’Hare, S.R. Leadley, A.J. Goodwin, Chemical Vapor Deposition 2005, 11, 477. [4] M. Creatore, F. Palumbo, R. d’Agostino, P. Fayet, Surface and Coatings Technology 2001, 142, 163. [5] J. Bardon, J. Bour, H. Aubriet, D. Ruch, B. Verheyde, R. Dams, S. Paulussen, R. Rego, D. Vangeneugden, Plasma Processes & Polymers 2007, 4, S445. [6] J. Bour, J. Bardon, H. Aubriet, D. Del Frari, B. Verheyde, R. Dams, D. Vangeneugden, D. Ruch, Plasma Processes & Polymers 2008, 5, 788. [7] C. Tendero, C. Texier, P. Tristant, J. Desmaison, P. Leprince, Spectrochimica Acta, Part B 2006, 61, 2. [8] F. Fanelli, S. Lovascio, R. d’Agostino, F. Arefi-Khonsari, F. Fracassi, Plasma Processes & Polymers 2010, 7, 535. [9] F. Fanelli, R. d’Agostino, F. Fracassi, Plasma Processes & Polymers 2011, 8, 932. [10] F. Fanelli, S. Lovascio, R. d’Agostino, F. Fracassi, Plasma Processes & Polymers 2012, 9, 1132. [11] V. Rouessac, S. Roualdes, J. Durand, Chemical Vapor Deposition 2002, 8, 155. [12] V. Barranco, P. Thiemann, H.K. Yasuda, M. Stratmann, G. Grundmeier, Applied Surface Science 2004, 229, 87. [13] P. Raynaud, B. Despax, Y. Segui, H. Caquineau, Plasma Processes & Polymers 2005, 2, 45. [14] F. Massines, N. Gherardi, A. Fornelli, S. Martin, Surface and Coatings Technology 2005, 200, 1855.
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Introduction
[15] M.S. Montaudo, Mass Spectrometry Reviews 2002, 21, 108.
[16] C. Wesdemiotis, N. Solak, M.J. Polce, D.E. Dabney, K. Chaicharoen, B.C. Katzenmeyer, Mass Spectrometry Reviews 2011, 30, 523.
[17] J. Bour, L. Charles, J. Petersen, M. Michel, J. Bardon, D. Ruch, Plasma Processes & Polymers 2010, 7, 687.
[18] G. Montaudo, C. Puglisi, F. Samperi, Polymer Bulletin 1989, 21, 483. [19] G. Montaudo, E. Scamporrino, D. Vitalini, Makromolecular Chemie Rapid Communications 1989, 10, 411. [20] G. Montaudo, E. Scamporrino, D. Vitalini, Polymer 1989, 30, 297. [21] G. Montaudo, E. Scamporrino, D. Vitalini, Macromolecules 1989, 22, 623. [22] G. Montaudo, E. Scamporrino, D. Vitalini, Macromolecules 1989, 22, 627.
Mass spectrometry is increasingly used for structural characterization of synthetic (co)polymers [15], allowing mass measurement of monomers in MS analysis and structural information by performing tandem mass spectrometric experiments, where intact cationic adducts of polymers are activated and their dissociation products analyzed based on fragmentation rules established for reference polymers with the same skeleton [16] {Part I, Chapter 3}. As a result, high resolution mass spectrometry was considered as the technique of choice to characterize plasma-polymers. However, a main analytical issue associated with plasma-polymer mass analysis is their very low solubility in most organic solvents. Preliminary works performed in our laboratory showed that soluble species (hence amenable to mass spectrometry analysis using conventional electrospray ionization [17]) could be extracted from thin films obtained upon plasmapolymerization of HMDSO. However, the lack of appropriate dissociation rules to understand MS/MS data obtained for these gas-phase ions prevented at that time any reliable structural features to be proposed. Moreover, soluble species constitute a very low amount of the whole sample (typically
