Thierry Fouquet

Tandem Mass Spectrometry of Trimethylsilyl-Terminated Poly(Dimethylsiloxane) Ammonium Adducts Generated by Electrospray Ionization

Ammonium adducts of trimethylsilyl-terminated poly(dimethylsiloxane) (CH3-PDMS) produced by electrospray ionization were submitted to collision induced dissociation and revealed a particular MS/MS behavior: the same three main product ions at m/z 221, 295, and 369 were always generated in very similar relative abundances regardless of the size of the precursor ion. Combining accurate mass measurements and ab initio calculation allowed very stable cyclic geometries to be obtained for these ionic species. Dissociation mechanisms were proposed to account for the three targeted ions to be readily generated in a two-step or a three-step reaction from any CH3-PDMS ammonium adducts. A second set of three product ions was also observed with low abundance at m/z 207, 281, and 355, which were shown in MS3 experiments to be formed in secondary reactions. An alternative dissociation process was shown to consist of a concerted elimination of ammonia and methane and the need for a methyl of an end-group to be involved in the released methane molecule would account for this reaction to mainly proceed from the smallest precursor ions.

Enhanced Adhesion over Aluminum Solid Substrates by Controlled Atmospheric Plasma Deposition of Amine-Rich Primers

Controlled chemical modification of aluminum surface is carried by atmospheric plasma polymerization of allylamine. The amine-rich coatings are characterized and tested for their behavior as adhesion promoter. The adhesion strength of aluminum-epoxy assemblies is shown to increase according to primary amino group content and coating thickness, which in turn can be regulated by plasma power parameters, allowing tailoring the coating chemical properties. The increase in adherence can be correlated to the total and primary amino group contents in the film, indicating covalent bonding of epoxy groups to the primer as the basis of the mechanical improvement.

MALDI SpiralTOF high‐resolution mass spectrometry and Kendrick mass defect analysis applied to the characterization of poly(ethylene‐co‐vinyl acetate) copolymers

Rationale Poly(ethylene‐co‐vinyl acetate) copolymers – usually referred to as EVA – are first class industrial polymers used for applications ranging from padding to photovoltaics as encapsulant for the silicon solar cells. Various techniques have been used for their characterization but the analysis of intact EVA chains using mass spectrometry (MS) has not been reported so far. Methods Three copolymers containing 18, 25 and 40 wt% vinyl acetate (VA) have been characterized using an off‐line coupling of size‐exclusion chromatography (SEC) and matrix‐assisted laser desorption/ionization (MALDI) spiral‐time‐of‐flight (TOF) high‐resolution mass spectrometry (HRMS). The representativeness of those results for the entire samples has been checked using 13C NMR spectroscopy. Lastly, Kendrick mass defect analysis has been proposed as an alternative and user‐friendly data treatment method. Results The shortest chains isolated by SEC fractionation and mass‐analyzed by HRMS have been thoroughly described in terms of end‐groups (found to be hydrogens) and co‐monomeric composition. The VA content was successfully derived from the peak assignments in MS spectra for the EVA 40 wt% and 25 wt% while it tended to be overestimated for the latest EVA 18 wt% (increasing poly(ethylene) character). Similar results have been found using a faster data treatment method relying on the Kendrick mass defect analysis of the MS data. Conclusions EVA low molecular weight intact oligomers have been extensively characterized by MS for the first time and the structural features confidently extended to the full sample according to NMR data. The Kendrick mass analysis finally constituted an efficient method for a fast evaluation of their VA content with no need for manual assignment.

Mechanistic investigation of a flame retardant coating made by layer-by-layer assembly

The efficiency of a flame retardant coating based on poly(allylamine) (PAH) and montmorillonite (MMT), deposited on polyamide 6 (PA6) bulk polymer was demonstrated in our previous work. In this paper we aim to investigate the mechanism of action of this flame retardant coating. To reach this objective, PA6-(PAH-MMT) at 40 bilayers was tested in a cone calorimeter and interrupted at different characteristic times: 25 s (after the fire test start), time to ignition, time of peak heat release rate and time of flameout. The condensed phases of the specimen residues obtained were characterized by scanning electron microscopy, X-ray diffraction, laser desorption ionization and solid state 13C nuclear magnetic resonance while the gas phase was evaluated by thermogravimetric analysis coupled with infrared spectroscopy and mass spectrometry. Finally the pyrolysis combustion flow calorimeter was used to evidence the effect of this layer-by-layer assembly in the gas phase. A possible mechanism explaining the improvement of the flame retardancy of a PA6 substrate in the presence of LbL coating made of PAH and clay is proposed.

Extension of the Kendrick Mass Defect Analysis of Homopolymers to Low Resolution and High Mass Range Mass Spectra Using Fractional Base Units

Beyond the high resolution/low mass range data traditionally used, a Kendrick mass defect analysis (KMD) using the new concept of fractional base units has been successfully conducted on low resolution/low mass range and high resolution/high mass range data for the first time. Relying on a mathematical framework to rationalize the effect of the fractional base units, the electrospray ionization single stage and multistage mass spectra of a poly(vinylpyrrolidone) recorded from a low resolution ion trap analyzer were turned into information-rich KMD plots using vinylpyrrolidone/112 and pyrrolidone/86 as base units. The distributions detected in the matrix assisted laser desorption ionization spiralTOF mass spectra of high molecular weight poly(ethylene oxide) and poly(caprolactone) were conveniently discriminated in KMD plots using (ethylene oxide)/45 and caprolactone/113 as base units with an unprecedented resolution at such a mass range. The high resolution KMD analysis using fractional base units opens new perspectives for the acquisition, visualization, and presentation of mass spectra of polymers with less restrictions in terms of required resolution and molecular weights.

Nano-ordered thin films achieved by soft atmospheric plasma polymerization

Plasma polymer thin films are of great interest in surface engineering in a wide range of applications. Herein, by using soft atmospheric plasma deposition parameters and by adapting these conditions to the used perfluorodecyl and dodecyl acrylates precursors, it is possible to get a high retention of monomer functionalities and a polymerization close to conventional methods. Molecular investigation revealed the presence of polymeric moieties and the mechanism of plasma polymerization has been mainly based on the polymerization by activation of the ethylenic groups. X-ray diffraction analyses have shown the presence of a smectic lamellar where the polyacrylate backbone was the amorphous phase and fluorinated and alkyl side chains were the hexagonal crystalline section. Wetting properties have been evaluated and finally showed hydrophobic surfaces

Taking MALDI SpiralTOF high‐resolution mass spectrometry and mass defect analysis to the next level with ethylene vinyl acetate vinyl alcohol terpolymers

Poly(vinyl alcohol)s (VOHs) and their derivatives constitute a peculiar class of polymer in the sense that the vinyl alcohol chain is not produced by the direct polymerization of its repeating unit. On the contrary, VOHs are usually produced by the controlled hydrolysis of vinyl acetate moieties from poly(vinyl acetate) chains (VA). The hydrolysis of VA to VOH has also been proposed for ethylene vinyl acetate copolymers (EVA) to produce terpolymers made of the repetition of three monomers (ethylene E, vinyl acetate VA and vinyl alcohol VOH) (Supplementary Fig. S1(A), Supporting Information) with promising properties for the preparation of polymer blends with improved mechanical properties or membranes. Chemical analysis such as infrared spectroscopy (IR) has been mainly employed to describe the EVAVOH terpolymers made from the partial hydrolysis of EVAwhile mass spectrometry (MS) has not been widely used so far in spite of its inherent assets for the characterization of copolymers. A full analytical strategy relying on the combination of size-exclusion chromatography (SEC) for a preliminary fractionation of the polymeric sample followed by high-resolution mass spectrometry (HRMS) and its Kendrick mass defect analysis (KMD) has been proposed recently for a thorough exploration of EVA samples. The complete methodology was mandatory owing to the isobaric issues arising from the elemental composition of the repeating units. The present letter deals with the extension of this analytical procedure for the characterization of partially hydrolyzed EVA copolymers. The nature of the three repeating units does indeed lead to even greater isobaric issues (Supplementary Fig. S1(B), Supporting Information) and the need for a high-resolution mass analyzer together with the simplified data visualization using mass defect analysis is more appropriate than ever. In particular, an unusual base unit for the calculation of the Kendrick masses – namely the mass difference between VA and VOH – is proposed in lieu of the repeating unit to highlight the hydrolytic route in a more visual and intuitive manner. Poly(ethylene-co-vinyl acetate) copolymer 40 wt% (abbreviated as EVA40), poly(vinyl alcohol) 9,000–10,000 g mol 1 80% hydrolyzed (i.e. a copolymer of vinyl acetate and vinyl alcohol with 80 mol% of VOH, noted as VAVOH80), trans-2-[3-(4-tertbutylphenyl)-2-methyl-2-propenylidene]malononitrile (DCTB), 2,5-dihydroxybenzoic acid, hydrochloric acid (HCl) and sodiumhydroxide (NaOH)were fromSigmaAldrich (St. Louis, MO, USA). Chloroform (CHCl3), tetrahydrofuran (THF) and ethanol were from Wako Pure Chemical Industries (Osaka, Japan). SEC fractionation of EVA40 was performed following the procedure described previously using a HLC-8220 GPC system (Tosoh, Tokyo, Japan) equipped with two TSKgel multipore HXL-M columns (Tosoh) in series and a refractive index (RI) detector (mobile phase: CHCl3 at 1 mL min , injection: 200 μL of a EVA40 solution in CHCl3 at 5 mg mL ). The fractions of interest were collected at 17 min 30 s to18 min (for IR spectroscopy, noted as #1) and 18 min 30 s to 19 min of elution (forMS, noted as #2) inmicro reaction vials and allowed to air dry. The hydrolysis of the EVA copolymer is based on the procedure described by Tang et al. but it was conducted directly in the vials (so-called ‘in-vial hydrolysis’, estimated amount of matter: ~30 μg in #1, ~6 μg in #2, Supporting Information). After adding 10 μL of THF to the micro reaction vials, the ‘pristine EVA’ samples were prepared by depositing 2 μL from vial #1 onto a gold-coated glass slide (Jasco Engineering Ltd, Tokyo, Japan) and by depositing 2 μL from vial #2 mixed with 5 μL of DCTB (10 mg mL 1 in THF) onto a non-hydrophobic target (Hudson Surface Technology Inc., Old Tappan, NJ, USA) for the IR andMS analyses, respectively. Then 2 μL of a 0.5M alcoholic NaOH solution was added to the vials and the mixture allowed to react. A volume of 2 μL of the reacting medium was removed by pipetting after 2 min and 20min and neutralizedwith 0.5 μL of 1MHCl. The neutralized solutions were finally deposited onto a gold-coated glass slide for IR analyses (vial #1) or mixed with 5 μL of DCTB in THF and deposited on a non-hydrophobic surface for MS analyses (vial #2). Fourier transform infrared reflection absorption spectroscopy (FTIR-RAS) spectra (128 scans) were obtained with a model 610 FTIR spectrometer (JASCO Corp., Tokyo, Japan) at a resolution of 2 cm 1 under inert atmosphere (nitrogen gas). Matrix-assisted laser desorption/ionization (MALDI) mass spectra were recorded using a JMS-S3000 SpiralTOFMS mass spectrometer (JEOL, Tokyo, Japan) using the parameters described elsewhere (and in Supporting Information). Kendrick masses (further noted as KM) were calculated using E (C2H4, mIUPAC/round(mIUPAC, 0) = 28.03130/ 28 Da) and C2H2O (42.0106/42 Da) as the base units. Accurate mass measurements on the IUPAC scale are converted to Kendrick masses as follows:

Photoageing of cardanol: characterization, circumvention by side chain methoxylation and application for photocrosslinkable polymers

The photosensitivity of cardanol has been evaluated using a multi-technique approach. Among other techniques, size exclusion chromatography, matrix assisted laser desorption ionization mass spectrometry and their off line coupling provided useful details on the macroscopically observed yellowing and insolubility of cardanol under UV activation by analyzing photoproducts at the molecular level. Evidencing the implication of the unsaturations borne by the cardanol side chain in a crosslinking process, an original synthesis route leading to its complete methoxylation has been proposed as a way to lower the photosensitivity of cardanol. Using a similar set of analytical techniques, this newly synthesized methoxylated cardanol has appeared more resistant towards UV exposure, without any crosslinking but a simple dimerization preserving its solubility. As a direct application, copolymers made from methyl methacrylate, cardanol and methoxylated cardanol have been synthesized, and their photocrosslinking ability was found to depend on the content of the two latter co-monomers, as a preliminary step towards the production of photocrosslinkable bio-based polymers with a tunable UV curing propensity.

Use of doubly charged precursors to validate dissociation mechanisms of singly charged poly(dimethylsiloxane) oligomers.

AbstractCollision-induced dissociation of doubly charged poly(dimethylsiloxane) (PDMS) molecules was investigated to provide experimental evidence for fragmentation reactions proposed to occur upon activation of singly charged oligomers. This study focuses on two PDMS species holding trimethylsilyl or methoxy end-groups and cationized with ammonium. In both cases, introduction of the additional charge did not induce significant differences in dissociation behavior, and the use of doubly charged precursors enabled the occurrence of charge-separation reactions, allowing molecules always eliminated as neutrals upon activation of singly charged oligomers to be detected as cationized species. In the case of trimethylsilyl-terminated oligomers, random location of the adducted charge combined with rapid consecutive reactions proposed to occur from singly charged precursors could be validated based on MS/MS data of doubly charged oligomers. In the case of methoxy-terminated PDMS, favored interaction of the adducted ammonium with both end-groups, proposed to rationalize the dissociation behavior of singly charged molecules, was also supported by MS/MS data obtained for molecules adducted with two ammonium cations. Figureᇵ

Convenient visualization of high-resolution tandem mass spectra of synthetic polymer ions using Kendrick mass defect analysis - the case of polysiloxanes.

High-resolution tandemmass spectrometry now constitutes a routine technique for the structural elucidation of polymer ions. While the nature of the repeating unit and the sum of the masses of the end-groups are evaluated by a single-stage mass spectrometry experiment (MS), a fragmentation step (MS/MS) is mandatory to decipher the chemical nature of each end-group individually or the shape of the backbone. MS/MS has thus been applied to a wide range of polymeric samples and a unified nomenclature for the product ions formed upon the dissociation of polymer ions has been proposed recently. However, the MS/MS spectra are often hard to visualize and describe owing to their complexity (number of product ions series and congeners in each series, isobaric product ions,...) while the presentation of MS/MS data to a wide audience remains an issue to be overcome. As proposed by Sato et al., using the repeating unit of a polymeric backbone as the base unit for the Kendrick masses (KM) allows fast visualization of homologous series from a MS spectrum in a so-called Kendrick mass defect (KMD) plot. Polymer ions from a homopolymer line up horizontally if they carry the same end-groups while the KMD values change when the nature of the end-groups changes. In the case of a blend, polymer ions with a repeating unit different from the base unit also depart from the horizontal alignment and line up in (an) oblique direction(s). When dealing with copolymers, the KMD plot turns into a scatter plot with an elliptical shape, extending in both the horizontal (co-monomer used as the base unit) and the oblique directions (the other co-monomer). KMD plots hence constitute a user-friendly data treatment andvisualization method of MS spectra from polymeric samples. Since the product ions formed during the collision-induced dissociation (CID) of a polymer ion (a) carry a varying number of repeating units in their backbone, (b) undergoparticular dissociation routes leading to the modification of one or several repeating units (e.g. release of a pendant group in the form of a neutral), (c) carrynone, one or the twopristine end-groups of the precursor ion, or (d) possess new end-groups formed during CID, the KMDvalues calculated from the accuratelymeasuredm/zvalues in a MS/MS spectrum would also exhibit useful alignments. Three examples of KMDplots are proposed here as an alternative and convenientway to visualize theCIDdata of poly(siloxanes) – a class of polymers of prime industrial importance – extensively commented on in other articles. Those studies have highlighted the influence of the end-groups and charge state or architecture of polysiloxanes on their MS/MS fingerprints that are sometimes difficult to describe precisely. The chosen examples comprise the CID of a (trimethylsilyl, methyl)-ended