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The molecular structure of a series of homo- and copolyesters was studied using sustained off-resonance irradiation collisionally activation dissociation on a Fourier transform ion cyclotron resonance mass spectrometer. Electrospray ionization was used as an ionization technique. The most important fragmentation pathways of the homopolyesters poly(dipropoxylated bisphenol-A/adipic acid) and poly(dipropoxylated bisphenol-A/isophthalic acid) were studied. Six different dissociation mechanisms were observed which are very similar to the mechanisms found to occur during pyrolysis of these compounds. Four of these mechanisms are a result of cleavages of the ester bond and the others are due to cleavages of the ether bond or bisphenol-A unit. Some of the fragments expected are not present in the spectrum, indicating that each fragment has a specific sodium affinity. Sequence-specific fragments of two of the three copolyester sequences that theoretically can exist were experimentally observed. Fragments that originate from the third sequence are not unique and can also be formed from other sequences. Therefore, it was not possible to determine the presence of the third sequence. Copyright 2000 John Wiley & Sons, Ltd.

The hardening of alkyd paints for do-it-yourself purposes is an autoxidation reaction with air oxygen. Since the crosslink reactions are hard to follow in an actual coating system, use is being made of model compounds. These are (m)ethyl esters of unsaturated fatty acids (linoleic and ricinoic) which contain the reactive substructures responsible for crosslinking of an alkyd. In this work, the oligomeric mixture resulting from crosslinking was studied with various mass spectrometric (MS) techniques : direct chemical ionization (DCI), fast atom bombardment (FAB), field desorption (FD), electrospray ionization (ESI) and secondary ion (SI) MS. Consistent results were obtained with all techniques : oligomers yielded signals consisting of groups of peaks 16 mass units apart, pointing to a series of oxygenated homologues. Differences were encountered, however, in the number of oligomers that could be seen with the various techniques. Using ESI-MS and SIMS, oligomer formation up to the tetramer (linoleic) or hexamer (ricinoic) was observed. DCI, FAB and FD generally yielded signals from dimers and trimers only. From the detailed ESI and DCI spectra, a difference in the crosslinking mechanism between conjugated and non-conjugated fatty acids becomes apparent (radical addition to the double bond or recombination of radicals, respectively). Also, using a mixture of the linoleic and ricinoic esters, mutual reaction between these two types of fatty acids can be demonstrated.