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Polymers 2018, 10(6), 672; https://doi.org/10.3390/polym10060672

On the Mechanisms of the Effects of Ionizing Radiation on Diblock and Random Copolymers of Poly(Lactic Acid) and Poly(Trimethylene Carbonate)

1
Institute of Applied Radiation Chemistry, Lodz University of Technology, Wroblewskiego 15, 93-590 Lodz, Poland
2
Department of Polymer Chemistry, Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, 90-363 Lodz, Poland
3
Department of Materials Science and Engineering, University of Maryland, 4418 Stadium Dr., College Park, MD 20742-2115, USA
*
Author to whom correspondence should be addressed.
Received: 9 May 2018 / Revised: 10 June 2018 / Accepted: 11 June 2018 / Published: 16 June 2018
(This article belongs to the Special Issue Radiation Effects in Polymers)
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Abstract

This article demonstrates that ionizing radiation induces simultaneous crosslinking and scission in poly(trimethylene carbonate-co-d-lactide) diblock and random copolymers. Copolymer films were electron-beam (EB) irradiated up to 300 kGy under anaerobic conditions and subsequently examined by evaluation of their structure (FT-IR, NMR), molecular weight, intrinsic viscosities, and thermal properties. Radiation chemistry of the copolymers is strongly influenced by the content of ester linkages of the lactide component. At low lactide content, crosslinking reaction is the dominant one; however, as the lactide ratio increases, the ester linkages scission becomes more competent and exceeds the crosslinking. Electron paramagnetic resonance (EPR) measurements indicate that higher content of amorphous carbonate units in copolymers leads to a reduction in free radical yield and faster radical decay as compared to lactide-rich compositions. The domination of scission of ester bonds was confirmed by identifying the radiolytically produced alkoxyl and acetyl radicals, the latter being more stable due to its conjugated structure. View Full-Text
Keywords: electron beam irradiation; crosslinking; scission; PLA; PTMC; poly(trimethylene carbonate-co-d-lactide); diblock copolymers; random copolymers; EPR; alkoxyl radicals; acetyl radicals electron beam irradiation; crosslinking; scission; PLA; PTMC; poly(trimethylene carbonate-co-d-lactide); diblock copolymers; random copolymers; EPR; alkoxyl radicals; acetyl radicals
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Adamus-Wlodarczyk, A.; Wach, R.A.; Ulanski, P.; Rosiak, J.M.; Socka, M.; Tsinas, Z.; Al-Sheikhly, M. On the Mechanisms of the Effects of Ionizing Radiation on Diblock and Random Copolymers of Poly(Lactic Acid) and Poly(Trimethylene Carbonate). Polymers 2018, 10, 672.

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