Qu B, Chen SM, Dai LM (2000) Simulation analysis of ESR spectrum of polymer alkyl-C-60 radicals formed by photoinitiated reactions of low-density polyethylene. Applied Magnetic Resonance 19(1), 59-67. [In English]

Web link: Keywords:

spin-trapping esr, cross-linking, c-60, fullerene, c60, resonance, rotation, styrene, epr,

Abstract: Polymer alkyl-fullerene (P-C-60) radical adducts produced by ultraviolet (UV) photoinitiated reactions between low-density polyethylene (LDPE) and C-60 in the presence of benzophenone (BP) as a photoinitiator have been detected and identified for the first time by electron spin resonance (ESR) and confirmed by simulation analysis of the spectrum. A well-resolved ESR spectrum was recorded in situ upon UV irradiation of the LDPE/BP/C-60 sample in the molten state (413 K). Detailed analysis of hyperfine structures shows that the observed spectrum is composed of three components: a broad singlet at g = 2.0025 from the C-60 radical anion, an innermost pair of C-13 satellites, and a 12-line spectrum superposed on the broad singlet. The simulation analysis of the spectrum shows that the 12-line spectrum is due to the overlapping of two kinds of radical adducts of tertiary carbon-C-60 (A) and secondary carbon-C-60 (B), which have slightly different g-values and almost the same integral intensity I-A/I-B (48.4/51.6). The spectrum simulated on the basis of the H-1 and 13C hyperfine interaction parameters is in good agreement with the observed spectrum. These results provide positive evidence that the C-60-bound LDPE materials can be obtained directly by a simple method of BP-photoinitiated reaction of the LDPE/C-60 system.