Evidence of Scission Products from Peroxide-Initiated Higher Temperature Polymerization of Alkyl Methacrylates

摘要

Methacrylates are a principal component of acrylic binder resins used in automotive coatings; the low molecular weight polymers with reactive functionalities are made via hightemperature starved-feed free-radical solution semibatch copolymerization. 1 The initiator, tert-butyl peroxyacetate (TBPA), is often chosen for experiments conducted at 130-150 SOHC due to its short half-life relative to the monomer feeding time.2 Scheme 1 illustrates the possible pathways for thermal decomposition of TBPA.3,4 One-bond scission generates two oxygen-centered radicals while two-bond scission yields a methyl radical, an oxygen-centered radical, and carbon dioxide. Studies inBuback’s group indicated that themethylcarbonyloxyl radical, if produced, undergoes fast decarboxylation before starting chain growth, as determined by the end-group analysis of the resultant polymers using electrospray ionization mass spectrometry (ESI-MS).