Assessing the Phosphate Distribution in Bioactive Phosphosilicate Glasses by P-31 Solid-State NMR and Molecular Dynamics Simulations
2014 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 118, no 29, 8863-8876 p.Article in journal (Refereed) Published
Melt-derived bioactive phosphosilicate glasses are widely utilized as bone-grafting materials for various surgical applications. However, the insight into their structural features over a medium-range scale up to similar to 1 nm remains limited. We present a comprehensive assessment of the spatial distribution of phosphate groups across the structures of 11 Na2O-CaO-SiO2-P2O5 glasses that encompass both bioactive and nonbioactive compositions, with the P contents and silicate network connectivities varied independently. Both parameters are known to strongly influence the bioactivity of the glass in vitro. The phosphate distribution was investigated by double-quantum 3113 nuclear magnetic resonance (NMR) experiments under magic-angle spinning (MAS) conditions and by molecular dynamics (MD) simulations. The details of the phosphate-ion dispersion were probed by evaluating the MD-derived glass models against various scenarios of randomly distributed, as well as clustered, phosphate groups. From comparisons of the P-P interatomic-distance spreads and the statistics of small phosphate clusters assessed for variable cutoff radii, we conclude that the spatial arrangement of the P atoms in phosphosilicate glasses is well-approximated by a statistical distribution, particularly across a short-range scale of <= 450 pm. The primary distinction is reflected in slightly closer P-P interatomic contacts in the MD-derived structures over the distance span of 450-600 pm relative to that of randomly distributed phosphate groups. The nature of the phosphate-ion dispersion remains independent of the silicate network polymerization and nearly independent of the P content of the glass throughout our explored parameter space of 1-6 mol % P2O5 and silicate network connectivities up to 2.9.
Place, publisher, year, edition, pages
2014. Vol. 118, no 29, 8863-8876 p.
Research subject Physical Chemistry
IdentifiersURN: urn:nbn:se:su:diva-106903DOI: 10.1021/jp504601cISI: 000339540600044OAI: oai:DiVA.org:su-106903DiVA: diva2:741252