engleski

Poly(ethylene oxide)/silica nanocomposites - Impact of the sample state on the outcome of γ-irradiation

γ-irradiation is a unique method of polymer modification that offers temperature-independent, clean and homogenous reaction initiation and results in a sterile product. On exposing to γ-irradiation poly(ethylene oxide), PEO, can both crosslink and degrade what impacts its crystallinity and numerous properties (mechanical, conductivity, etc). The overall outcome depends on the irradiation conditions and PEO characteristics and their interplay [1]. Addition of nanoparticles to polymer materials is known to improve mechanical properties in particular and to reduce crystallinity of semicrystalline polymers [2] but interaction of irradiation and nanoparticle addition is poorly investigated field. PEO/silica nanocomposite films were modified and nanocomposite gels were prepared by γ-irradiation up to 100 kGy, in air or under nitrogen. Thermal analysis, optical microscopy, X-ray diffraction and FTIR spectroscopy revealed that outcome mostly depended on the state of PEO matrix on irradiation and that the state of the sample also influenced the effect of nanosilica addition while its concentration was less significant. Nanosilica induced heterogenous nucleation and increased crystallinity proportional to its concentration in unirraddited films. In PEO/nano-SiO2 solid films irradiated in air nanosilica did not provide radiation resistance but probably enhanced oxidative degradation by increasing content of the more radiation sensitive amorphous phase. It might facilitate crystallization of broken chains on irradiation of nanocomposite films resulting in additional crystallinity increase of samples irradiated to 50 kGy and significant deterioration of mechanical properties at higher doses, especially for samples irradiated in contact with air. In the same dose range irradiation PEO/nano- SiO2 aqueous solutions produced crosslinked nanocomposite gels of much lower crystallinity and better mechanical properties. Radiochemical effects of nanosilica likely contributed to further reduction of crystallinity in nanocomposite gels. Pronounced changes on addition of 20 wt % of nano- SiO2 to both nanocomposite films and gels indicate a possible synergism of γ-irradiation and nanoparticle addition.

poly(ethylene oxide) ; silica ; nanocomposites ; γ-irradiation ; films ; gels

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