Modifications induced by swift heavy ions on poly(hydroxybutyrate–hydroxyvalerate) (PHB/HV) and poly( ε-caprolactone) (PCL). : Part 2. Radicals characterization

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Vol. 171; no. 4; pp. 499 - 508
• Main Authors: Rouxhet, L., Mestdagh, M., Legras, R.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2000
• Subjects: Electron spin paramagnetic resonance; Irradiation; Poly( ε-caprolactone); Poly(hydroxyalkanoate); Irradiation; Poly( ε-caprolactone); Poly(hydroxyalkanoate); Electron spin paramagnetic resonance
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/S0168-583X(00)00314-1

Modifications induced by different energetic heavy ions ( 40 Ar 9+ , 80 Kr 15+ , 129 Xe 24+ , 208 Pb 53+ and 208 Pb 56+ ) on poly( ε-caprolactone) (PCL) and poly(hydroxybutyrate–hydroxyvalerate) (PHB/HV) have been investigated by electron spin resonance (ESR). Indeed, film irradiation by heavy ions leads to, among other phenomena, the formation of radicals in the ion tracks. Thanks to ESR, it is possible to detect these radicals and to identify them or at least to characterize them by following the evolution of the radical signal as a function of parameters, like temperature, or the kinetic of disappearance of the radical species at ambient temperature in vacuum or ambient atmosphere. This study confirmed the generation of radicals by the irradiation of PHB/HV samples with energetic heavy ions reported in the literature. The study on PCL was not pursued after a few preliminary studies, revealing the presence of an ESR signal in the non-irradiated sample. Electronic stopping power has a major influence on radical decrease at ambient temperature. The ion used for the irradiation did not modify very much the radical signal and the evolution of the radicalar signal intensity with temperature. Different reasoning and experiments revealed that the glass transition temperature is a key temperature above which irreversible recombinations of the most stable radicals take place. A simulation study indicated that the most stable radical produced was probably a tertiary radical formed by the stabilization of the secondary radical resulting from the abstraction of a highly mobile hydrogen adjacent to the carbonyl.