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The logarithmic relaxation process and the critical temperature of liquids in nano-confined states

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ABSTRACT

The logarithmic relaxation process is the slowest of all relaxation processes and is exhibited by only a few molecular liquids and proteins. Bulk salol, which is a glass-forming liquid, is known to exhibit logarithmic decay of intermediate scattering function for the β-relaxation process. In this article, we report the influence of nanoscale confinements on the logarithmic relaxation process and changes in the microscopic glass-transition temperature of salol in the carbon and silica nanopores. The generalized vibrational density-of-states of the confined salol indicates that the interaction of salol with ordered nanoporous carbon is hydrophilic in nature whereas the interaction with silica surfaces is more hydrophobic. The mode-coupling theory critical temperature derived from the QENS data shows that the dynamic transition occurs at much lower temperature in the carbon pores than in silica pores. The results of this study indicate that, under nano-confinements, liquids that display logarithmic β-relaxation phenomenon undergo a unique glass transition process.

No MeSH data available.


Self-intermediate scattering function of salol in different states at different measured temperatures with a Q value of 1.0 Å−1.Salol confined in Carbon pore (39 ± 1 Å) (a), Carbon pore (56 ± 1 Å) (b), Silica pore (40 ± 1 Å) (c) and Silica pore (60 ± 1 Å) (d). Inset: the self-intermediate scattering function of bulk salol. The solid lines are fits with equation (3).
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f2: Self-intermediate scattering function of salol in different states at different measured temperatures with a Q value of 1.0 Å−1.Salol confined in Carbon pore (39 ± 1 Å) (a), Carbon pore (56 ± 1 Å) (b), Silica pore (40 ± 1 Å) (c) and Silica pore (60 ± 1 Å) (d). Inset: the self-intermediate scattering function of bulk salol. The solid lines are fits with equation (3).

Mentions: The self-intermediate scattering function, Φ(Q, t) of salol in the bulk as well as in the confined states were obtained by Fourier transformation of S(Q, ω), deconvolution of the instrument resolution, and normalization with the value at t = 0. The bulk salol shows a clear logarithmic relaxation process on the timescale of 0.2–15 ps while confinement of salol in either carbon or silica pores did not hinder the logarithmic relaxation process (see Fig. 2). The following asymptotic formula derived from mode-coupling theory (MCT) is used for expressing the self-intermediate scattering function373839.


The logarithmic relaxation process and the critical temperature of liquids in nano-confined states
Self-intermediate scattering function of salol in different states at different measured temperatures with a Q value of 1.0 Å−1.Salol confined in Carbon pore (39 ± 1 Å) (a), Carbon pore (56 ± 1 Å) (b), Silica pore (40 ± 1 Å) (c) and Silica pore (60 ± 1 Å) (d). Inset: the self-intermediate scattering function of bulk salol. The solid lines are fits with equation (3).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037365&req=5

f2: Self-intermediate scattering function of salol in different states at different measured temperatures with a Q value of 1.0 Å−1.Salol confined in Carbon pore (39 ± 1 Å) (a), Carbon pore (56 ± 1 Å) (b), Silica pore (40 ± 1 Å) (c) and Silica pore (60 ± 1 Å) (d). Inset: the self-intermediate scattering function of bulk salol. The solid lines are fits with equation (3).
Mentions: The self-intermediate scattering function, Φ(Q, t) of salol in the bulk as well as in the confined states were obtained by Fourier transformation of S(Q, ω), deconvolution of the instrument resolution, and normalization with the value at t = 0. The bulk salol shows a clear logarithmic relaxation process on the timescale of 0.2–15 ps while confinement of salol in either carbon or silica pores did not hinder the logarithmic relaxation process (see Fig. 2). The following asymptotic formula derived from mode-coupling theory (MCT) is used for expressing the self-intermediate scattering function373839.

View Article: PubMed Central - PubMed

ABSTRACT

The logarithmic relaxation process is the slowest of all relaxation processes and is exhibited by only a few molecular liquids and proteins. Bulk salol, which is a glass-forming liquid, is known to exhibit logarithmic decay of intermediate scattering function for the β-relaxation process. In this article, we report the influence of nanoscale confinements on the logarithmic relaxation process and changes in the microscopic glass-transition temperature of salol in the carbon and silica nanopores. The generalized vibrational density-of-states of the confined salol indicates that the interaction of salol with ordered nanoporous carbon is hydrophilic in nature whereas the interaction with silica surfaces is more hydrophobic. The mode-coupling theory critical temperature derived from the QENS data shows that the dynamic transition occurs at much lower temperature in the carbon pores than in silica pores. The results of this study indicate that, under nano-confinements, liquids that display logarithmic β-relaxation phenomenon undergo a unique glass transition process.

No MeSH data available.