Polycarboxylic acids as network modifiers for water durability improvement of inorganic–organic hybrid tin-silico-phosphate low-melting glasses

We investigated the water durability of the inorganic–organic hybrid tin-silico-phosphate glasses Me2SiO–SnO–P2O5 (Me designs the organic methyl group) doped with organic acids (salicylic acid (SA), tartaric acid (TA), citric acid (CA) and butane tetracarboxylic acid (BTCA)) containing one or more of carboxylic groups per molecule. The structure, thermal properties and durability of the final glasses obtained via a non-aqueous acid–base reaction were discussed owing to the nature and the concentration of the acid added. 29Si magic angle spinning (MAS) NMR and 31P MAS NMR spectra, respectively, showed clearly a modification of the network in the host glass matrix of the Me2SiO–SnO–P2O5 system. The polycondensation enhancement to form –P–O–Si–O–P– linkages (PSP) and the increase of the Q2 unit (two bridging oxygens per phosphorus atom) over the Q3 unit (three bridging oxygens per phosphorus atom) as a function of the acid in the order SA