Poly(ethylene oxide) irradiated in the solid state, melt and aqueous solution—a DSC and WAXD study

Interactions of the aggregate state of poly(ethylene oxide), PEO, and γ-irradiation conditions (total dose, atmosphere) on its thermal and crystalline properties were investigated by DSC and WAXD taking into account sample molecular mass and form. In PEO irradiated in the solid state and in the presence of oxygen, chain scission dominated over concurrent crosslinking up to 200 kGy, particularly in PEO powders, due to a large surface being in contact with air. In solid samples the degree of crystallinity and crystallite size increased with the dose up to 50 kGy, probably not just due to partial crystallization upon degradation of amorphous phase, but to recrystallization of broken tie molecules. The least changes in crystallinity and phase transformation temperatures occurred in solid films. A substantial decrease in crystallinity and transformation temperatures without the initial crystallinity increase was achieved in samples that were amorphous on irradiation, at temperatures above the PEO melting temperature and in aqueous solutions. Radiation crosslinking of the PEO aqueous solution in an inert atmosphere is the most suitable way to obtain a lower degree of crystallinity and phase transformation temperatures while preserving mechanical properties.

► We studied radiation conditions and PEO characteristics effects in a systematic way.
► We focused on the interactions between gamma-irradiation and PEO properties.
► DSC and WAXD detected the greatest influence of PEO aggregate state during irradiation.
► Degradation dominated in the solid state and crosslinking prevailed in aqueous solutions.
► Atmosphere is a significant factor, whereas the PEO form and molecular mass are less important