Abstract:Conformational characteristics of 1-butanol incorporated not only in hexagonal and lamellar aggregates formed by a lyotropic liquid crystal composed of sodium octanoate, 1-butanol, and water but also in a thermotropic liquid crystal, 4'-methoxybenzylidene-4-n-butylaniline (MBBA), have been investigated from 2H NMR quadrupolar splittings of the perdeuterated and partially deuterated compounds. In the lyotropic phases, 1-butanol shows strong trans preferences and renders itself extended, and octanoate decreases … Show more
“…28 Conversely, analogous hydrocarbon systems comprising sodium octanoate and either octan-1-ol or decan-1-ol show extremely rich phase behaviour, forming a variety of mesophases including lamellar, hexagonal, reverse hexagonal and rod-like structures. 26,27,29 The likely reason for the difference in structural behaviours is that the solubility of the components is much greater for the hydrocarbon system. This is characterised by the fact that the critical micelle concentration of sodium octanoate at ca.…”
Highly ordered silica was synthesised by using a lamellar phase comprising the anionic fluorinated surfactant sodium perfluorooctanoate and the partially-fluorinated co-surfactant/oil 1H,1H,2H,2H-perfluorooctan-1-ol in water. The phase behaviour of this system was thoroughly analysed, and it was found that even low levels of the alcohol (<0.5 mol%) were sufficient to induce a phase change from normal micelles to a lamellar phase, rationalised as a result of geometric and electrostatic effects. The properties of these phases were compared to their hydrocarbon analogues, demonstrating the unique and valuable properties exhibited by fluorocarbons, directly related with the observed nanostructure. Small-angle neutron scattering was used to analyse the internal structure of the systems, providing information on the inter-lamellar spacing, bilayer thickness and membrane elasticity. The potential for these phases to act as shear-thinning lubricants was assessed using oscillatory rheology, obtaining shear-dependent viscosity along with storage and loss moduli.
“…28 Conversely, analogous hydrocarbon systems comprising sodium octanoate and either octan-1-ol or decan-1-ol show extremely rich phase behaviour, forming a variety of mesophases including lamellar, hexagonal, reverse hexagonal and rod-like structures. 26,27,29 The likely reason for the difference in structural behaviours is that the solubility of the components is much greater for the hydrocarbon system. This is characterised by the fact that the critical micelle concentration of sodium octanoate at ca.…”
Highly ordered silica was synthesised by using a lamellar phase comprising the anionic fluorinated surfactant sodium perfluorooctanoate and the partially-fluorinated co-surfactant/oil 1H,1H,2H,2H-perfluorooctan-1-ol in water. The phase behaviour of this system was thoroughly analysed, and it was found that even low levels of the alcohol (<0.5 mol%) were sufficient to induce a phase change from normal micelles to a lamellar phase, rationalised as a result of geometric and electrostatic effects. The properties of these phases were compared to their hydrocarbon analogues, demonstrating the unique and valuable properties exhibited by fluorocarbons, directly related with the observed nanostructure. Small-angle neutron scattering was used to analyse the internal structure of the systems, providing information on the inter-lamellar spacing, bilayer thickness and membrane elasticity. The potential for these phases to act as shear-thinning lubricants was assessed using oscillatory rheology, obtaining shear-dependent viscosity along with storage and loss moduli.
“…Good understanding of molecular structure of aliphatic alcohols in diluted phase is crucial for comprehension of the formation of a complex hydrogen-bonded structure in single phase. The conformational equilibrium of aliphatic alcohols, and in particular the internal rotation about C–O(H) bond, has attracted constant attention ,− with very recent report involving pulsed jet FT microwave spectroscopy and quantum mechanical study as a good example . Moreover, subtle effects of hydrogen bonding leadings to the formation of various heteroclusters in a binary alcohol/water and alcohol/hydrocarbon mixtures have recently been reported; these microscale effects are believed to be expressed directly as heterogeneity of such binary systems observed experimentally by NIR spectroscopy. , The coexistence of conformational isomers and the impact of temperature and concentration on conformational equilibria of contributing alcohol may play a role in the formation of such heteroclusters.…”
Conformational isomerism of aliphatic alcohols with respect to the internal rotation of C-O(H) group and its impact on near-infrared (NIR) spectra has been known in the literature. However, no attempt has ever been made to investigate systematically whether and how the conformational flexibility of the aliphatic chain determines the observed NIR data of aliphatic alcohols. In the present study NIR spectra of four kinds of butyl alcohols, 1-butanol, 2-butanol, isobutanol, and tert-butyl alcohol, were investigated in diluted (0.1 M) CCl solutions. The experimental NIR spectra of butyl alcohols were accurately reproduced and explained in a fully anharmonic DFT study by means of generalized second-order vibrational perturbation theory (GVPT2). Entire conformational populations were taken into account in each case. On the basis of the theoretical study, influences of conformational flexibility with respect to internal rotations not only about the C-O bond, but also about the C-C bonds have been well evidenced in the experimental spectra. The conformational isomerism affects significantly the shape of NIR spectra. The temperature-dependent NIR spectra of butyl alcohols show changes in the band shape and a blue-shift of the overtone band due to the stretching mode of free OH group, and its intensity decreases with increasing temperature. These effects can be closely monitored by two-dimensional correlation spectroscopy (2D-COS). In this work, the experimental 2D-COS patterns have been successfully reproduced, based on DFT calculated NIR spectra of conformational isomers of the studied molecules and their Boltzmann coefficients over the corresponding temperature range. Thus, the experimentally observed effects are fully reflected in the DFT study, which leads to the conclusion that the main factor in the temperature-dependent spectral changes of 2ν band of aliphatic alcohols in the diluted phase, where no self-association occurs, is played by the changes in the relative population of their conformational isomers.
“…Since the hydroxyl groups of the alcohols are supposedly “locked” in the headgroup regions of the surfactants and the hydrocarbon chains of the alcohols are shorter than those of the surfactants, the incorporation of the alcohols should create “gaps” in the surfactant hydrocarbon group regions. Indeed, the surfactant alkyl groups are known to acquire less extended conformations in the mixed surfactant−alcohol aggregates than in the alcohol-free aggregates . Conversely, alcohols have more extended conformations in the mixed aggregates than in the free state. , Thus, the decreases in the surfactant hydrocarbon group order can result from the need to compensate the mismatch in the lengths of the hydrocarbon groups of the alcohol and surfactant.…”
Section: Resultsmentioning
confidence: 99%
“…Indeed, the surfactant alkyl groups are known to acquire less extended conformations in the mixed surfactant−alcohol aggregates than in the alcohol-free aggregates . Conversely, alcohols have more extended conformations in the mixed aggregates than in the free state. , Thus, the decreases in the surfactant hydrocarbon group order can result from the need to compensate the mismatch in the lengths of the hydrocarbon groups of the alcohol and surfactant. 6 The effect of the C 16 Py + concentration on the anisotropy of the DPH fluorescence at 30 °C in the BIC in the absence of alcohols (solid diamonds) and in the presence of 1-butanol (0.1 M, open circles) or 1-dodecanol (0.05 mM, open triangles).…”
Block ionomer complexes (BIC) of "dual hydrophilic" block copolymers containing ionic and nonionic blocks and oppositely charged surfactants spontaneously form colloidal particles of ca. 80 nm in diameter stable in aqueous dispersions at every composition of the mixture. Packing and dynamics of aliphatic groups of the surfactant in BIC were examined by using the quenching-resolved fluorescence anisotropy (QRFA) method with 1,6-diphenyl-1,3,5-hexatriene (DPH) as a probe. The values of the order parameter and rotational relaxation time in the BIC were higher than those in the surfactant micelles. Incorporation of aliphatic alcohols in the BIC decreased the order parameter and increased the rotational relaxation time. The effects on the order parameter were explained by changes in the surfactant aliphatic group conformation to "fill the gaps" induced by insertion of shorter alcohol molecules. The effects on the relaxation time were attributed to a decrease in repulsion of the surfactant headgroups and expulsion of water from the BIC hydrophobic interior as evidenced by the decrease in micropolarity. The results of this study have implications for potential use of the BIC in pharmaceutics and other fields.
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