Initiation of free‐radical polymerization by peroxypivalates studied by electrospray ionization mass spectrometry

Initiation by tert-butyl peroxypivalate (TBPP), tert-amyl peroxypivalate (TAPP), 1,1,3,3-tetramethylbutyl peroxypivalate (TMBPP), or 1,1,2,2-tetramethylpropyl peroxypivalate (TMPPP) of radical polymerization of methyl methacrylate in toluene solution at 90 °C was studied via polymer end-group analysis using electrospray ionization mass spectrometry (ESI-MS). Conclusive peak assignments allowed for measuring the type and concentration of the fragments that actually initiate macromolecular growth after thermal decomposition of these peroxypivalates. It was found that the pivaloyloxy radical moiety undergoes instantaneous decarboxylation to yield an initiating tert-butyl radical. The alkoxy radical moiety, on the other hand, may generate, via β-scission reaction, different types of carbon-centered radicals (together with a ketone) or may undergo a 1,5-H-shift reaction, by which reaction an oxygen-centered radical is transformed into a carbon-centered hydroxy radical. This hydrogen shift reaction was found in case of TMBPP. Surprisingly, no evidence for initiating alkoxy radicals could be found, not even in case of initiation by TBPP, where the intermediate tert-butoxy radical undergoes a rapid chain-transfer reaction with the solvent toluene.

[1]  C. Barner‐Kowollik,et al.  Reversible Addition Fragmentation Chain Transfer (RAFT) Polymerization of Methyl Acrylate: Detailed Structural Investigation via Coupled Size Exclusion Chromatography−Electrospray Ionization Mass Spectrometry (SEC−ESI-MS) , 2004 .

[2]  M. Kling,et al.  A seemingly well understood light-induced peroxide decarboxylation reaction reinvestigated with femtosecond time resolution. , 2003, Journal of the American Chemical Society.

[3]  C. Grimm,et al.  Ultrafast Decarboxylation of Carbonyloxy Radicals: Influence of Molecular Structure , 2003 .

[4]  Xulin Jiang,et al.  Mass spectrometric characterization of functional poly(methyl methacrylate) in combination with critical liquid chromatography. , 2003, Analytical chemistry.

[5]  L. Radom,et al.  The reversible addition-fragmentation chain transfer process and the strength and limitations of modeling: Comment on “the magnitude of the fragmentation rate coefficient” , 2003 .

[6]  Shiping Zhu,et al.  A difference of six orders of magnitude: A reply to “the magnitude of the fragmentation rate coefficient” , 2003 .

[7]  M. Arnould,et al.  Functionalization of polymeric organolithium compounds with formaldehyde , 2003 .

[8]  Kenzo Inoue,et al.  Anionic polymerization of methyl methacrylate initiated with late transition‐metal halides/organolithium/triisobutylaluminum systems , 2003 .

[9]  B. Abel,et al.  Ultraschnelle Decarboxylierung organischer Peroxide in Lösung: Zusammenspiel unterschiedlicher spektroskopischer Techniken, Quantenchemie und theoretischer Modellierung , 2003 .

[10]  Leonie Barner,et al.  Reversible addition–fragmentation chain‐transfer polymerization: Unambiguous end‐group assignment via electrospray ionization mass spectrometry , 2002 .

[11]  M. Buback,et al.  Initiator efficiency of peroxides in high‐pressure ethene polymerization , 2002 .

[12]  C. Barner‐Kowollik,et al.  End-group analysis of polymers by electrospray ionization mass spectrometry: 2-Methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one initiated free-radical photopolymerization , 2002 .

[13]  J. Hartung,et al.  Selectivity in the chemistry of oxygen-centered radicals: The formation of carbon-oxygen bonds , 2002 .

[14]  Yasumasa Watanabe,et al.  Study of alkyl radicals fragmentation from 2-alkyl-2-propoxyl radicals , 2002 .

[15]  C. Barner‐Kowollik,et al.  Laser‐induced decomposition of 2,2‐dimethoxy‐2‐phenylacetophenone and benzoin in methyl methacrylate homopolymerization studied via matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry , 2002 .

[16]  L. Radom,et al.  Factors Controlling the Addition of Carbon-Centered Radicals to Alkenes-An Experimental and Theoretical Perspective. , 2001, Angewandte Chemie.

[17]  L. Prokai.  Characterization of Macromolecules by Electrospray lonization Mass Spectrometry , 2001 .

[18]  S. Hanton,et al.  Mass spectrometry of polymers and polymer surfaces. , 2001, Chemical reviews.

[19]  J. Scrivens,et al.  Characterisation of synthetic polymer systems , 2000 .

[20]  M. Buback,et al.  Pressure and Temperature Dependence of the Decomposition Rate of Aliphatic tert-butyl Peroxyesters , 2000 .

[21]  M. Nielen.  Accurate end group determination of low molecular weight polymers by electrospray ionization time-of-flight mass spectrometry , 1999 .

[22]  E. Rizzardo,et al.  Initiation mechanisms for radical polymerization of styrene and methyl methacrylate with highly substituted peroxypivalate initiators , 1999 .

[23]  P. Derrick,et al.  Probing the effects of cone potential in the electrospray ion source:  consequences for the determination of molecular weight distributions of synthetic polymers. , 1998, Analytical chemistry.

[24]  W. J. Simonsick,et al.  Application of mass spectrometry to the characterization of polymers , 1997 .

[25]  E. Rizzardo,et al.  FREE RADICAL INITIATION MECHANISMS IN THE POLYMERIZATION OF METHYL METHACRYLATE AND STYRENE WITH 1,1,3,3-TETRAMETHYLBUTYL PEROXYPIVALATE: ADDITION OF NEOPENTYL RADICALS , 1997 .

[26]  E. Rizzardo,et al.  Reaction of tert-Alkoxyl and Alkyl Radicals with Styrene Studied by the Nitroxide Radical-Trapping Technique , 1997 .

[27]  Yasumasa Watanabe,et al.  Temperature Dependence of Initiation Reactions of Oxygen-Centered Radicals , 1997 .

[28]  D. Haddleton,et al.  Evaluation of the Mode of Termination for a Thermally Initiated Free-Radical Polymerization via Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry , 1997 .

[29]  D. Haddleton,et al.  Mass Discrimination Effects in an Ion Detector and Other Causes for Shifts in Polymer Mass Distributions Measured by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry , 1996 .

[30]  E. Rizzardo,et al.  Initiation Mechanisms for Radical Polymerization of Methyl Methacrylate with tert-Butyl Peroxypivalate , 1996 .

[31]  R. Bateman,et al.  The Application of Matrix‐assisted Laser Desorption/Ionization Combined with Collision‐induced Dissociation to the Analysis of Synthetic Polymers , 1996 .

[32]  D. Haddleton,et al.  Electrospray ionisation mass spectrometry (ESI MS) of poly(methyl methacrylate) and acrylic statistical copolymers , 1996 .

[33]  M. H. Back,et al.  Rate constants for abstraction of hydrogen from benzene, toluene, and cyclopentane by methyl and ethyl radicals over the temperature range 650–770 K , 1989 .