Collect. Czech. Chem. Commun. 1985, 50, 1699-1713

A study of decay mechanism of alkyl macroradicals in polyisobutylene

Josef Bartoš

Institute of Polymers, Chemical Research Centre, Slovak Academy of Sciences, 842 36 Bratislava


The macroradicals generated in polyisobutylene by γ-radiolysis at 77 K have been studied from the point of view of their structure and reactivity with the use of the ESR method and various kinetic models. In the region of 223-243 K a single type of macroradicals is only present, ~C(CH3)2CHC(CH2)2~, these radicals being decayed according to the second order kinetics with effective activation energy of 77.5 kJ mol-1. This result was interpreted within the model of diffusion-controlled reactions using the activation energy approach. Various potential mechanisms of transport of the centres have been tested on the molecular level. Approach of the reactants is controlled by intermolecular hydrogen transfer connected with quasi-crankshaft motions of the chain segments, and at suitable conditions, especially at early stages of the decay, it is possible also to consider a physical mechanism of approach of near-standing reactants with participation of crankshaft motions of the chain segments.