Abstract
Unsaturated low molar mass species were identified via ESI-MS after fractionation of poly(butyl acrylate) from high temperature radical polymerization.
Highlights
In addition to the above-described reactions, the midchain radical may undergo a β scission reaction, which is important to account for at high temperatures.[20,21,22,23,24,25,26,27,28,29,30,31,32] As illustrated in Scheme 1, β scission yields a molecule with a terminal double bond and a chain end radical
The polymer was activated at 140 °C and the products were analyzed via electron spray ionization – mass spectrometry (ESI-MS).[33,34]
size-exclusion chromatography (SEC) analyses of the products clearly indicate that a significant fraction of low molar mass species is formed
Summary
In addition to the above-described reactions, the midchain radical may undergo a β scission reaction, which is important to account for at high temperatures.[20,21,22,23,24,25,26,27,28,29,30,31,32] As illustrated in Scheme 1, β scission yields a molecule with a terminal double bond and a chain end radical. If the midchain radical is formed by a backbiting reaction – as shown in Scheme 1 – the chain lengths of both species will be very different. Scheme 1 β scission reactions of a midchain radical obtained from backbiting via 1,5 H shift In this contribution the notations MMnvCH2 and MMnH are used for unsaturated and saturated species, respectively, that may be identified in the ESI-MS spectra up to m/z of 1800 Da. A second aspect that needs to be considered is that the tertiary radicals generated via backbiting were reported to migrate along the polymer backbone. The polymer was activated at 140 °C and the products were analyzed via electron spray ionization – mass spectrometry (ESI-MS).[33,34] The spectra clearly showed a distribution of macromonomers of different chain length rather than a single m/z obtained via β scission at one distinct monomer unit of the macromonomer. Mass spectrometry analyses and in particular ESI-MS proved to be important for getting more insight into the β scission and subsequent migration mechanism.[28,33,34,39,40,41]
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