Influence of APTES-Decorated Mesoporous Silica on the Dynamics of Ethylene Glycol MoleculesInsights from Variable Temperature 2H Solid-State NMR

• Published in: Journal of physical chemistry. C 2023-10, Vol.127 (39), p.19735-19746
• Main Authors: Haro Mares, Nadia B., Brodrecht, Martin, Wissel, Till, Döller, Sonja C., Rösler, Lorenz, Breitzke, Hergen, Hoffmann, Markus M., Gutmann, Torsten, Buntkowsky, Gerd
• Format: Article
• Language: English
• Subjects: C: Physical Properties of Materials and Interfaces
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.3c03671

The physicochemical effects of decorating pore walls of high surface area materials with functional groups are not sufficiently understood, despite the use of these materials in a multitude of applications such as catalysis, separations, or drug delivery. In this study, the influence of 3-amino-propyl triethoxysilane (APTES)-modified SBA-15 on the dynamics of deuterated ethylene glycol (EG-d 4) is inspected by comparing three systems: EG-d 4 in the bulk phase (sample 1), EG-d 4 confined in SBA-15 (sample 2), and EG-d 4 confined in SBA-15 modified with APTES (sample 3). The phase behavior (i.e., melting, crystallization, glass formation, etc.) of EG-d 4 in these three systems is studied by differential scanning calorimetry. Through line shape analysis of the 2H solid-state NMR (2H ssNMR) spectra of the three systems recorded at different temperatures, two signal patterns, (i) a Lorentzian (liquid-like) and (ii) a Pake pattern (solid-like), are identified from which the distribution of activation energies for the dynamic processes is calculated employing a two-phase model.