An EPR, ENDOR and EIE study of γ-irradiated poly (lactide-co-glycolide) polymers
✍ Scribed by James A. Bushell; Mike Claybourn; Damien M. Murphy; Helen E. Williams
- Publisher
- John Wiley and Sons
- Year
- 2006
- Tongue
- English
- Weight
- 304 KB
- Volume
- 44
- Category
- Article
- ISSN
- 0749-1581
- DOI
- 10.1002/mrc.1880
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✦ Synopsis
Abstract
Gamma radiation of poly (lactide‐co‐glycolide) raw polymers and processed microspheres under vacuum and at 77 K results in the formation of a series of free radicals. The resulting powder electron paramagnetic resonance (EPR) spectrum contains a distribution of several different radicals, depending on the annealing temperature, and is therefore difficult to interpret. By utilising the selectivity of the electron nuclear DOuble resonance (ENDOR) and associated ENDOR induced EPR (EIE) techniques, a more direct approach for the deconvolution of the EPR spectrum can be achieved. Using this approach, the radiolytically induced CH~3~^•^CHC(O)R‐ chain scission radical was identified at 120 K by simulation of the EIE spectrum. At elevated temperatures (250 K), this radical decays considerably and the more stable radicals ‐O^•^CHC(O)‐, CH~3~^•^C(OR)C(O)‐ and CH~3~^•^C(OH)C(O)‐ predominate. This work demonstrates the utility of the EIE approach to supplement and aid the interpretation of powder EPR spectra of radicals in a polymer matrix. Copyright © 2006 John Wiley & Sons, Ltd.