Abstract
AbstractDissolution of phosphates bioglasses, for bone regeneration or controlled ion release, is a key property to be tuned by adequate selection of chemical species. Mixed Na‐Sr and Na‐Ca polyphosphate glasses exhibit definite bonding preferences of the stronger cations to O from chain‐end phosphates (Q1) instead of random bonding to the network (Q1 and Q2). This behavior is important for the control of dissolution, as hydration starts from the reaction of H with O in Q1. To analyze this bonding preference in glasses with two alkaline earths competing for O, mixed Na‐Ca‐Sr polyphosphates (0.57‐x) Na2O·x/2 SrO·x/2 CaO·0.43 P2O5 (0 ≤ x ≤ 0.30 molar fraction) were considered. 31P nuclear magnetic resonance was used to analyze the short‐range environments of Qn groups, detecting preferential bonding of Ca and Sr to Q1. To probe variations in the medium‐range organization of the network induced by Ca or Sr, glasses with compositions (0.57‐x) Na2O·x MO·0.43 P2O5 (M = Ca,Sr; 0 ≤ x≤0.30 molar fraction), were analyzed using 31P‐double‐quantum techniques. An increase in mutual Q2 self‐connectivity relative to the base Na‐polyphosphate network was detected as Ca or Sr were added, indicating conversion of linear phosphate chains into rings.
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