Are hydrogen supramolecular structures being suppressed upon nanoscale confinement? The case of monohydroxy alcohols

Impact of Confinement on the Dynamics and H-Bonding Pattern in Low-Molecular Weight Poly(propylene glycols)

“…The values of the heat capacity and calculated thickness of the interfacial layer are listed in Table and Figure . As observed, the estimated ξ reaches similar values for all PPGs when infiltrated into native silica membranes (within experimental uncertainty), which are comparable to those ones reported earlier for 2E1H or for monohydroxy alcohols, where the value of ξ oscillated around ∼1 nm. However, after the silanization, ξ decreases for PPG-OH and PPG-NH 2 because of change in the interfacial interaction ( i.e.…”

“…In this context, it should be mentioned that the similar finding has been recently reported for a primary and secondary monohydroxy alcohols incorporated within alumina and silica pores. It was shown that the temperature dependences of the Debye relaxation times, τ D (reflecting the mobility of supramolecular self-assemblies , ), deviate from the bulk-like behavior at approximately the same τ D irrespectively of the porous template, chemical structure, and architecture of the supramolecular structures formed in the studied systems . Moreover, recently Tu et al found the same scenario in ionic liquids confined in the native and functionalized alumina pores.…”

“…It was shown that the temperature dependences of the Debye relaxation times, τ D (reflecting the mobility of supramolecular self-assemblies 47,48 ), deviate from the bulklike behavior at approximately the same τ D irrespectively of the porous template, chemical structure, and architecture of the supramolecular structures formed in the studied systems. 49 Moreover, recently Tu et al 50 found the same scenario in ionic liquids confined in the native and functionalized alumina pores. This indicates that the change in the porous template, hydrophobicity, or hydrophilicity of the pore surface does not affect segmental dynamics of the interfacial layer to much because the bifurcation of τ α (T)-dependences of the core PPGs occurs at similar τ α (log τ α ∼ −5.5).…”

“…It must be also stressed that above discussed results obtained for confined PPGs differ from those obtained for water or alcohols infiltrated in nanoporous templates. For primary alcohols incorporated to the native and silanized silica pores, we have found that the strength of H-bonds in confined samples was weaker compared to those in bulk systems which was manifested in the IR spectra as the blueshift of the ν O–H peak frequency . In the case of water confined in zeolites, the O–H bands were slightly redshifted with respect to bulk water, indicating, that under confinement, molecules are relatively strongly hydrogen-bonded .…”

“…For primary alcohols incorporated to the native and silanized silica pores, we have found that the strength of H-bonds in confined samples was weaker compared to those in bulk systems which was manifested in the IR spectra as the blueshift of the ν O−H peak frequency. 49 In the case of confined in zeolites, the O−H bands were slightly redshifted with respect to bulk water, indicating, that under confinement, molecules are relatively strongly hydrogen-bonded. 64 Moreover, the IR spectra of water confined in controlled pore glasses proved that this fluid is perturbed on very large scales (more than 10 nm), even in pores of greater diameter (d = 55 nm).…”