An ESR study of the gamma radiolysis of aromatic polyesters containing isomeric naphthalene links

Hill, David J. T.; Choi, Bong-Ku; Ahn, Hung-Kun; Choi, E‐Joon

doi:10.1016/s0969-806x(01)00438-8

Cited by 5 publications

References 13 publications

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Radiation Chemistry of Polymers

Hill

Whittaker

2004

Encyclopedia of Polymer Science and Technology

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Polymeric materials are exposed to high energy radiation either deliberately to alter their properties or inadvertently during their use in high dose environments. As a consequence, an understanding of how radiation modifies the polymer structure, and hence properties, is essential for many applications. In addition, the understanding of the degradation of polymers with light or heat can benefit from knowledge of the reaction pathways of radical and charged species formed on irradiation with high energy photons. This article aims to provide a broad overview of the fundamental processes occurring during radiolysis of polymers. This is achieved through a discussion of the interaction of high energy photons with matter, and the subsequent reactions of mainly radical intermediates. Polymers either cross‐link or degrade on exposure to radiation, and the final properties of the polymers depend critically on the balance of these two main reaction pathways. A number of examples are taken from the literature to illustrate how the tendency to undergo cross‐linking or main‐chain scission depends on the polymer structure. The overall yield of reactions can be greatly reduced by the introduction of aromatic groups into the polymer structure. On the other hand, yields can be increased by the inclusion of radiation‐sensitive groups such as sulfones. Similarly, the rates of reactions and the balance between cross‐linking and scission can depend sensitively on the radiolysis temperature. While this review focuses on a discussion of the reactions occurring on radiolysis in vacuo, the effect of the presence of dissolved oxygen on the reaction pathways is also discussed.

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Radiation Chemistry of Polymers

Hill

Whittaker

2004

Encyclopedia of Polymer Science and Technology

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Radiation Chemistry of Polymers

Hill

Whittaker

2016

Encyclopedia of Polymer Science and Technology

View full text Add to dashboard Cite

Polymeric materials are exposed to high energy radiation either deliberately to alter their properties or inadvertently during their use in high dose environments. As a consequence, an understanding of how radiation modifies polymer structure, and hence properties, is essential for many applications. In addition, the understanding of the degradation of polymers with light or heat can benefit from knowledge of the reaction pathways of radical and charged species formed on irradiation with high energy photons. This article aims to provide a broad overview of the fundamental processes occurring during radiolysis of polymers. This is achieved through a discussion of the interaction of high energy photons with matter, and the subsequent reactions of mainly radical intermediates. Polymers either cross‐link or degrade on exposure to radiation, and the final properties of the polymers depend critically on the balance of these main reaction pathways. Examples are taken from the literature to illustrate how the tendency to undergo cross‐linking or main‐chain scission depends on the polymer structure. The overall yield of reactions can be greatly reduced by the introduction of aromatic groups into the polymer structure. On the other hand, yields can be increased by the inclusion of radiation‐sensitive groups such as sulfones. Similarly, the rates of reactions and the balance between cross‐linking and scission can depend sensitively on the radiolysis temperature. While this review focuses on a discussion of the reactions occurring on radiolysisin vacuo, the effect of the presence of dissolved oxygen on the reaction pathways is also briefly addressed.

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Radiation‐induced effects in gamma‐irradiated PLLA and PCL at ambient and dry ice temperatures

Walo

Przybytniak

Nowicki

et al. 2011

J of Applied Polymer Sci

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The effect of c-rays sterilization at ambient (23 C) and at dry ice temperatures (À78 C) on two biodegradable semicrystalline polyesters, namely poly(L-lactide) (PLLA) and poly(e-caprolactone) (PCL), was studied. The radical processes generated by irradiation were investigated by electron paramagnetic resonance (EPR) spectroscopy, whereas postradiation changes were monitored for 5 months by scanning calorimetry, thermogravimetric analysis, and apparent viscosity measurements. It was confirmed that the radiation sterilization initiates degradation in both studied polymers, however, the effect is smaller in PCL than in PLLA, and that the range of changes might be limited by lowering temperature of the exposure to c-rays. Newly formed oxygen containing functional groups confirmed by EPR and thermogravimetric analysis methods are produced in the irradiated polyesters. In PCL, the process might give rise to thermally induced cross-linking via oxygen containing intermolecular bridges. During storage, in both irradiated materials, morphology determined by differential scanning calorimetry is changing -PCL ability toward crystallization decreases insignificantly, whereas in PLLA the tendency is opposite -on irradiation a contribution of crystalline phase is growing considerably, from 18 and 19% to 41 and 31% for PLLA irradiated at 23 C and at À78 C, respectively.

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An ESR study of the gamma radiolysis of aromatic polyesters containing isomeric naphthalene links

Cited by 5 publications

References 13 publications

Radiation Chemistry of Polymers

Radiation Chemistry of Polymers

Radiation Chemistry of Polymers

Radiation‐induced effects in gamma‐irradiated PLLA and PCL at ambient and dry ice temperatures

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