Abstract
It has been found that field desorption mass spectrometry was one of the most useful methods to analyze the distribution of molecular weight, polymerization initiator and reaction mechanism in polyalkylene oxides.
The mass spectra of polypropylene glycols showed two series of quasi-molecular ion peak patterns, repeating every 58 mass units corresponding to the monomer unit C3H6O, I+58n+1 and I+58n+23 (I: molecular weight of polymerization initiator). The latter series of peak patterns correspond to the mass number of each cluster ions with sodium molecule. In the same way, the mass spectrum of polyethylene glycol showed two series of repetitive quasimolecular ion peak patterns, I+44n+1 and I+44n +23. In addition to analyzing main composition units and initiators, the distribution of molecular weight in these polymers could be estimated from the intensities of each peak height. High molecular compounds whose molecular weight, near 1,000, could not be detected by conventional CI-MS and by GC with silyl derivatives, were identified very easily by this method.
The mass spectrum of block copolymer showed characteristic ion peak patterns composed of numerous ion peak groups. The distribution of molecular weight of polyethylene oxide and polypropylene oxide parts in the block copolymer and the information of reaction mechanism could be deduced from the accumulated intensities of all ions containing the same additive mole number of ethylene oxide or propylene oxide monomer.
