Surface Properties and Reactivity of Phosphate-based Glasses by Inverse Gas Chromatography and Dynamic Vapour Sorption

The chemical durability of phosphate-based glasses (PGs) in an aqueous environment is crucial in determining their dissolution properties and their ultimate performance in vivo. In this study, inverse gas chromatography (IGC) and dynamic vapour sorption (DVS)were used to investigate the short-term aqueous interactions of PG particles doped with SiO2 and TiO2 (50P2O5-40CaO-xSiO2- (10-x)TiO2, where x=7, 5, 3, and 0 mol%). IGC was used to evaluate the solubility parameter and surface energy of PGs. A good correlation between the polar parts of the solubility parameter and surface energy with glass transition temperature (Tg) and dissolution rates was demonstrated. DVS was applied to monitor the sorption characteristics of the PG particles. An increase in silica content resulted in greater vapour sorption and mass change. Nuclear magnetic resonance spectroscopy data of the PGs post exposure to vapour demonstrated that increased SiO2 content disrupted the glass network and formed protonated phosphate species. Fourier transform infrared spectroscopy verified the presence of non-reacted water molecules in the PGs depending on SiO2 content. Moreover, there was a good correlation between the values measured through IGC and DVS, demonstrating the ability of both techniques in predicting the dissolution properties of PGs as consequence of alterations in their chemistry.