engleski

Characterization of poly(ethylene oxide) and its nanocomposites prepared by gamma-irradiation methods

Poly(ethylene oxide), (PEO), is a semicrystalline polymer with numerous applications (hydrogels, polyelectrolytes, etc.). γ-irradiation is a suitable method of polymer modification offering temperature-independent, clean and homogenous reaction initiation and resulting in a sterile product. It is known that under irradiation PEO can both crosslink and degrade what impacts its crystallinity, mechanical properties, conductivity, active substance release etc. Irradiation conditions and PEO characteristics are the factors that determine overall outcome and their interplay is not well studied. Addition of nanoparticles is known to improve especially mechanical properties and in some cases electrical conductivity of polymer materials. Yet, interaction of irradiation and nanoparticle addition is poorly investigated. The radiation stabilization due to some fillers was reported. It was also noted that by combining the effect of TiO2 addition and irradiation significant increase of conductivity in PEO electrolytes can be achieved. The aim of this work was to study the interactions of nano-SiO2 addition and 60Co γ-irradiation on properties of PEO nanocomposites prepared in different ways. The results were compared to the effects observed in pure PEO irradiated in two aggregate states. In both cases irradiation atmosphere and total dose were varied. The changes brought by irradiation were investigated by DSC, WAXD, FTIR and optical microscopy. We found that the γ-irradiation dose and the aggregate state of pure PEO samples are the most important factors determining the outcome. Chain scission dominated in PEO irradiated in the solid state and in the presence of oxygen and resulted in an increase in crystallinity and crystallite size at lower doses. That increase did not occur on irradiating PEO at temperatures above its melting or in aqueous solution. Due to effective crosslinking irradiation in the aqueous solution proved to be the most suitable way for obtaining PEO samples of lower degree of crystallinity and phase transformation temperatures. By irradiation of PEO/SiO2 nanocomposite films degradation prevailed. While in unirradiated PEO/SiO2 films nucleating effect of filler is seen, in irradiated ones it is compensated resulting in overall crystallinity increase at lower doses and deterioration of mechanical properties at higher. This indicates that nanosilica enhances degradation or/and facilitates crystallization of broken chains if samples are irradiated in solid state. Irradiation of aqueous solutions of PEO containing nano-SiO2 resulted in nanocomposite gels of significantly lower crystallinity and phase transformation temperatures than in nanocomposite films. Nanosilica additionally decreases crystallinity compared to pure PEO gels so almost amorphous samples were obtained at relatively low dose. Pronounced changes observed in samples with 20 wt% of nano-SiO2 indicate a sinergistic effect of γ-irradiation and nanoparticles. Although nanosilica did not increase radiation resistance of PEO it provided a manner of obtaining samples of the lowest degree of crystallinity for a particular irradiation conditions.

poly(ethylne oxide); gamma-irradiation; silica; nanocomposites; film; aqueous solution; degree of crystallinity; DSC; WAXD; FTIR

nije evidentirano