Effect of Nanopore Geometry in the Conformation and Vibrational Dynamics of a Highly Confined Molecular Glass
| Autor: | Steven M. Hurney, Carlos Morillo, Haonan Wang, Aaron Bond, Kenneth L. Kearns, Yi Jin, Ahmad Arabi Shamsabadi, Zahra Fakhraai, Aixi Zhang |
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| Rok vydání: | 2021 |
| Předmět: |
Quantitative Biology::Biomolecules
Materials science Nanoporous Mechanical Engineering Relaxation (NMR) Bioengineering 02 engineering and technology General Chemistry Weak interaction 021001 nanoscience & nanotechnology Condensed Matter Physics symbols.namesake Nanopore Chemical physics Intramolecular force symbols General Materials Science 0210 nano-technology Glass transition Raman spectroscopy Porous medium |
| Zdroj: | Nano letters. 21(4) |
| ISSN: | 1530-6992 |
| Popis: | The effect of nanoporous confinement on the glass transition temperature (Tg) strongly depends on the type of porous media. Here, we study the molecular origins of this effect in a molecular glass, N,N'-bis(3-methylphenyl)-N,N'-diphenylbenzidine (TPD), highly confined in concave and convex geometries. When confined in controlled pore glass (CPG) with convex pores, TPD's vibrational spectra remained unchanged and two Tg's were observed, consistent with previous studies. In contrast, when confined in silica nanoparticle packings with concave pores, the vibrational peaks were shifted due to more planar conformations and Tg increased, as the pore size was decreased. The strong Tg increases in concave pores indicate significantly slower relaxation dynamics compared to CPG. Given TPD's weak interaction with silica, these effects are entropic in nature and are due to conformational changes at molecular level. The results highlight the role of intramolecular degrees of freedom in the glass transition, which have not been extensively explored. |
| Databáze: | OpenAIRE |
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