Radiolysis of polyisobutene IV: A study of the role of free radicals in the fracture reaction using radioactive additives

摘要: Abstract The influence of additives on the formation polymer radicals and macromolecular fractures in polyisobutene by exposure to 4 MeV electrons has been studied using phenyl-3H-sec-butyl-35S1-disulphide, thiophenol-3H, thiophenol-35S, nitrobenzene-14C. G(polymer radicals) was found decrease from a maximum value 7·3 at concentration thiophenol 3 5 × 10−4 mole/g 4·5 5·4 about 15 then remain constant. As this may be due partly scavenging H · CH3 precursors, it is supposed that primary are formed processes which relatively insensitive presence large concentrations ‘protective agent’. Comparison effects yields leads conclusion two types radical formed. One fracture CH CCH3 bonds, 4·2 ⩾ G(—) ⩾2.7, other direct main chain carbon atoms, G(—·) 3·1. Nitrobenzene-14C, only slightly soluble, combines with polymer, G(combined nitrobenzene) = 1·2, increases G(fractures) 0·6 after dose Mrad. An explanation suggested for contrasting nitrobenzene low concentrations. Thiophenol reduces yield stabilizing — preventing β-bond scission. Nitrobenzene fails do but instead further ‘fracture-offsetting’ combination radicals, —·, scission —.