Supramolecular x-ray signature of susceptibility amplification in hydrogen-bonded liquids

Abstract

Mixing two nonconducting hydrogen-bonded liquids, each exhibiting a low dielectric relaxation strength, can result in a highly electrically absorbing fluid. This susceptibility amplification effect is demonstrated for mixtures of monohydroxy alcohols. Whereas in the pure liquids a tendency to form ringlike low-dipole moment clusters prevails, in the mixtures such supramolecular structures are disfavored leading to an up to tenfold enhancement of the dielectric loss. The compositional evolution of density and mean cluster-cluster separation is traced using x-ray scattering and indicates deviations from ideal mixing with decreased C-C but simultaneously increased O-O correlation lengths. Thus, the variation in the supramolecular absorption strength could be tracked using a static scattering technique. These observations are in harmony with volume exclusion and ring open effects that predict an optimized susceptibility amplification for mixtures in which the two components occupy equal volume fractions as experimentally observed.

Impact of Hydrogen Bonding on Dynamics of Hydroxyl-Terminated Polydimethylsiloxane

“…The composite spectra displayed in Figure a suggest that this is indeed the case. Actually, the dielectric response of HO-PDMS-OH550 is in many aspects very similar to the one observed for associating MAs such as 4-methyl-3-heptanol or 2-buthyl-1-octanol …”

“…Actually, the dielectric response of HO-PDMS-OH550 is in many aspects very similar to the one observed for associating MAs such as 4-methyl-3heptanol 46 or 2-buthyl-1-octanol. 47 Analysis of the dielectric spectra reveals that the slow process gains amplitude and approaches the faster process as temperature decreases. The ratio of their relaxation strengths and of their relaxation times vary from Δε I /Δε II ≈ 3.5 and τ max,I /τ max,II ≈ 135 at T = 212 K to Δε I /Δε II ≈ 5.3 and τ max,I /τ max,II ≈ 109 at T = 172 K, respectively.…”

Oscillatory shear and high-pressure dielectric study of 5-methyl-3-heptanol

“…The phenomenon that g K =1 is crossed while changing various external-state variables is not restricted to 5M3H. It is also shown by other neat alcohols such as, e.g., 2-methyl-2hexanol [23] and 2-butyl-1-octanol [17,56]. A ring-to-chain equilibrium may also be expected to appear when mixing the ring-former 4M3H with the chain-former 2E1H.…”

“…The insights obtained by studying these substances can also enhance the understanding of the properties of other (hydrogen-bonded) systems including water and bio-macromolecules. While the Debye-like relaxation was long believed to be experimentally accessible only via dielectric [9,10] and related spectroscopies [11][12][13], recent investigations demonstrate that also nuclear magnetic resonance [14], oscillatory shear [15], quasi-elastic neutron scattering [16], and even structural studies [17] may be sensitive to this feature.…”

Isomeric effects in structure formation and dielectric dynamics of different octanols

“…This microstructure is controlled by the length 4,5 and the branching 6 of the carbon tail and the position of the hydroxyl group 7 and can be classified by cyclic, linear or more complex associates like lassos and branched chains or loops. Interestingly, the ap-pearance and dominant type of structural arrangements are supposed to dependent on temperature [8][9][10] and pressure [11][12][13] as inferred from dielectric spectroscopy [14][15][16][17][18][19] , rheology [20][21][22] , calorimetry 23,24 , vibrational spectroscopy 25,26 , molecular dynamics simulations [27][28][29][30] and a combination of experimental and theoretical methods [31][32][33][34] . An overview can be found in Böhmer et al 3 .…”