The surface melting of octamethylcyclotetrasiloxane confined in controlled pore glasses as studied by 1H-NMR
2007 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 111, no 7, 1574-1581 p.Article in journal (Refereed) Published
We have measured the thickness of the pre-molten surface layer that appears at the interface of octamethylcyclotetrasiloxane (OMCTS) to the matrix in controlled pore glasses with pore diameters ranging 7.5-73 nm. Except for the glass with the largest pores, the layer thickness data for different pore diameters fall on a single master curve when plotted versus T-m - T, where T-m is the size-dependent volume melting point of the pore-confined OMCTS. Hence, at a single temperature, the surface layer thickness depends strongly on the curvature of the pore wall and therefore that of the solid-liquid interface. For temperatures where it exceeds two monolayers, the layer thickness depends logarithmically on T-m - T; for the glass with the largest pores, this turns into a power law with the exponent -1/2. The results are interpreted in terms of a continuous model of the solid-liquid interface with an arbitrary curvature. Because OMCTS is a weakly polar molecule with close to spherical shape, our data also lend themselves to Lennard-Jones type simulations.
Place, publisher, year, edition, pages
2007. Vol. 111, no 7, 1574-1581 p.
1st-order bulk transitions, ice surfaces, solid-surfaces, porous silica, water, liquid, nmr, size, adsorption, spectroscopy
IdentifiersURN: urn:nbn:se:kth:diva-6454DOI: 10.1021/jp0654765ISI: 000244225100012ScopusID: 2-s2.0-33847787458OAI: oai:DiVA.org:kth-6454DiVA: diva2:11172
Uppdaterad från submitted till published: 20100927.
QC 201009272006-11-292006-11-292010-09-27Bibliographically approved