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  • 1
    Electronic Resource
    Electronic Resource
    Influence of Tacticity on Polymer Surfaces Studied by ToF-SIMS (1997)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 25 (1997), S. 41-45 
    Details
    ISSN: 0142-2421
    Keywords: ToF-SIMS ; polymer toxicity ; poly(methylmethacrylate) ; polystyrene ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Poly(methylmethacrylate) (PMMA) and polystyrene (PS) thin films of different tacticities have been analysed by time-of-flight (ToF) SIMS in order to look for a possible influence of the stereoregularity on their fingerprint spectra (m/z≤200). Because, at first glance, the spectra of samples with different tacticities seemed rather similar, the intensity ratios between secondary ions from main polymer chain and those from pendant group were evaluated. By this procedure, it was found that isotactic PMMA can be clearly distinguished from syndiotactic and atactic PMMA. A lower concentration of the methyl-methacrylate pendant group was detected at the surface of the isotactic sample. In the case of PS, more phenyl groups were found to be present at the surface of isotactic PS and an empirical criterion is proposed to differentiate between atactic and isotactic PS. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 1 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Static SIMS spectra of polystyrene obtained by ‘living’ radical polymerization. Part I: Molecular weight-dependent fragmentation (1998)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 26 (1998), S. 569-578 
    Details
    ISSN: 0142-2421
    Keywords: polystyrene ; molecular weight ; ToF-SIMS ; fragmentation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A series of low-polydispersity polystyrenes with molecular weight ranging from 2000 to 130000 were synthesized by atom transfer radical polymerization and analyzed by time-of-flight secondary ion mass spectrometry. The end groups obtained by this polymerization process were hydrogen at one end and bromine at the other end. The molecular structure of the end groups and the molecular weight of the chains were found to influence significantly the absolute intensities of the end-group parent ions and the characteristic polystyrene fragments. For their formation, two different mechanisms have to be taken into account: direct scission and rearrangement before the emission.The absolute intensities of the end-group fragments in positive and negative modes exhibit a decrease when the molecular weight decreases. The protonated repeat unit fragments ([M+H]+ or C8H9+ at m/z=105) and bromide ions (Br- at m/z=79 and 81) are produced by a direct scission mechanism of the respective end groups. Meanwhile, the tropylium ion intensity (C7H7+ at m/z=91) increases for the low-molecular-weight (Mn) samples. This ion cannot be produced by a direct scission but a reorganization process of the polymer structure is required before the fragment emission.It is shown that, in static SIMS, the sensitivity towards the end group and then towards the molecular weight is dependent on the stability, the electroaffinity and/or the ionization potential of the ions formed from the end group. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 11 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    ToF-SIMS quantification of polystyrene spectra based on principal component analysis (PCA)† (1997)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 25 (1997), S. 878-888 
    Details
    ISSN: 0142-2421
    Keywords: molecular weight ; polymer ; polystyrene ; ToF-SIMS ; principal component analysis ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Monodisperses polystyrenes (PS) with molecular weight (Mn) ranging from 850 to 20000 g mol-1 and with different butyl end-groups have been analysed by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Only the fingerprint part of the spectra (m/z〈200) has been considered. This part comes from the fragmentation of the macromolecules and this is the only contribution in the secondary ion spectra of bulk polymers. In a former study, it has been shown that Mn has a significant influence on the PS secondary molecular ion intensities. It was found that not only the end-group characteristic ion intensities are modified for Mn〈50000 g mol-1, but also those related to main chain fragments. In this study, the possibility to use this effect to quantify the molecular weight of the macrochains at the surface is investigated. Because the quantification method should preferably include all the information contained in the spectra (over 150 peaks), statistical methods are needed. Principal component analysis is applied to these ToF-SIMS data. Principal component analysis builds the best linear combination of the variables, namely the principal components that describe the greatest amount of variation of the sample set. It is found that only one principal component is required to account for the molecular weight variations and a second one allows the samples to be discriminated depending on their butyl end-groups. Whatever the PS end-groups (linear, secondary or tertiary butyl), the correlation found between the first principal component and the sample molecular weight leads to the definition of a universal curve that allows the molecular weight determination for an unknown monodisperse PS sample. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 9 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Static SIMS spectra of polystyrene obtained by ‘living’ radical polymerization. Part II: Molecular weight quantification based on end groups (1998)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 26 (1998), S. 579-589 
    Details
    ISSN: 0142-2421
    Keywords: polystyrene ; molecular weight ; ToF-SIMS ; quantification ; error ; end groups ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A series of low-polydispersity polystyrenes with molecular weight ranging from 2000 to 130000 synthesized by atom transfer radical polymerization were analyzed by time-of-flight secondary ion mass spectrometry. The polymer end groups obtained by this polymerization process are hydrogen at one end and bromide at the other end.The great sensitivity of these end groups towards the ion beam-induced emission yield of secondary ion fragments allows the direct quantification of the molecular weight of the polystyrene at the surface. However, before applying any quantification method, several steps have to be performed: the peak assignment of the characteristic end group fragments and the choice of the spectrum normalization method. The influence of two normalization procedures is compared for two quantification methods - the characteristic peak intensity ratios and a chemometric method (principal component analysis) - in order to achieve molecular weight determination of the polystyrene at the surface. It is shown that, depending on the normalization procedure used, very different results can be obtained for both quantification methods. The validity of the procedures is also discussed. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 9 Ill.
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