“Weak links” in polystyrene—thermal degradation of polymers prepared with AIBN or benzoyl peroxide as initiator
1989; Elsevier BV; Volume: 25; Issue: 7-8 Linguagem: Inglês
10.1016/0014-3057(89)90043-8
ISSN1873-1945
AutoresJulia Krstina, Graeme Moad, David H. Solomon,
Tópico(s)Polymer Nanocomposites and Properties
ResumoPolystyrene has been prepared with 13C-labelled initiators and 13C NMR spectroscopy used to evaluate the role of initiator-derived functionality in the thermal degradation at 300°C. Changes in the molecular weight and molecular weight distribution were measured by GPC. For polymers prepared with benzoyl-carbonyl-13C peroxide or benzoyl-α-13C peroxide, the end groups incorporated by head addition or transfer to initiator/primary radical termination (secondary benzoate esters) undergo rapid elimination at 300° and must be considered potential “weak links”. However, benzoate end groups formed by “tail” addition to monomer (primary benzoates) are relatively stable at 300° and are not “weak links”. Phenyl end groups are also stable at 300°. Experiments with model compounds show that the unsaturated ends of the type formed by elimination of the benzoate end groups are labile at 300°. Studies on polymers prepared with AIBN-α-13C show that both cyanoisopropyl ends and copolymerized methacrylonitrile appear stable at 300° and are unlikely to be “weak links”. Possible causes of anomolous behaviour of high conversion polystyrene prepared with benzoyl peroxide with respect to the variation in molecular weight distribution on thermolysis are discussed in terms of the initiator-derived and other structural irregularities.
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