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Two series of Aerosol-OT-analoguesurfactants (sulfosuccinate-typedi-BCnSS and sulfoglutarate-type di-BCnSG) with hyperbranched alkyl double tails(so-called “hedgehog” groups, carbon number n= 6, 9, 12, and 18) have been synthesized and shown todemonstrate interfacial properties comparable to those seen for relatedfluorocarbon (FC) systems. Critical micelle concentration (CMC), surfacetension at the CMC (γCMC), and minimum area per molecule(Amin) were obtained from surface tensionmeasurements of aqueous surfactant solutions. The results were examinedfor relationships between the structure of the hedgehog group andpacking density at the interface. To evaluate Aand Bvalues in the Klevens equation for these hedgehog surfactants,log(CMC) was plotted as a function of the total carbon number in thesurfactant double tail. A linear relationship was observed, producing Bvalues of 0.20–0.25 for di-BCnSS and di-BCnSG, compared to avalue of 0.31 for standard double-straight-tail sulfosuccinate surfactants.The lower Bvalues of these hedgehog surfactantshighlight their lower hydrophobicity compared to double-straight-tailsurfactants. To clarify how hydrocarbon density in the surfactant-taillayer (ρlayer) affects γCMC, theρlayerof each double-tail surfactant was calculatedand the relationship between γCMCand ρlayerexamined. As expected for the design of low surface energysurfactant layers, ρlayerwas identified as an importantproperty for controlling γCMCwith higher ρlayer, leading to a lower γCMC. Interestingly,surfactants with BC9and BC12tails achievedmuch lower γCMC, even at low ρlayervalues of <0.55 g cm–3. The lowest surfaceenergy surfactant studied here was di-BC6SS, which hada γCMCof only 23.8 mN m–1. Sucha low γCMCis comparable to those obtained with shortFC-tail surfactants (e.g., 22.0 mN m–1for the sulfosuccinate-typeFC-surfactant with R = F(CF2)6CH2CH2−). [ABSTRACT FROM AUTHOR]

After preparing a homologous series of tetrameric mesogenic compounds in which two U-shaped molecules were connected via a rigid benzene derivative or a flexible alkyl chain, we investigated their phase transition behaviour using optical microscopy, differential scanning calorimetry and X-ray diffraction analysis. The compounds possessing an alkyl spacer as the central group exhibited nematic and smectic A phases just as the corresponding U-shaped molecule did. The compound possessing a 1,2-benzene unit as the connecting group showed nematic and smectic A phases, although the compound possessing a 1,3-benzene unit exhibited only an anticlinic smectic C phase. Structure-property relations of the liquid crystalline tetramers are interpreted in terms of preorganised effects of the four mesogenic units. [ABSTRACT FROM AUTHOR]

We synthesized novel liquid crystal tetramers possessing cyanobiphenyl and phenylpyrimidine moieties, and investigated their phase transition behavior. The liquid crystal tetramers exhibited nematic (N) and smectic A (SmA) phases. X-ray diffraction measurements suggest that the SmA phase has an intercalated structure. We discuss the transition behavior of the newly designed tetramers in terms of their molecular shape. [ABSTRACT FROM AUTHOR]

Novel oligomeric compounds in which three mesogenic moieties are connected via 3,4-dihydroxybenzoic acid or 3,5-dihydroxybenzoic acid were prepared and the physical properties investigated. Some of the compounds were found to have a tendency to form glassy states. With respect to 4-cyanobiphenyl-4'-yl 4-octyloxy-2-(3,4-bis{6-[4-(5-octylpyrimidine-2-yl)phenyloxy]hexyloxybenzoyloxy)benzoate, it is possible to obtain a supercooled nematic phase despite it deviating from a strongly rod-like structure. We discuss intermolecular interactions between neighbouring mesogenic parts for the appearance of the nematic phase. [ABSTRACT FROM AUTHOR]

A homologous series of novel liquid crystal trimers in which cyanobiphenyl and phenylpyrimidine moieties are connected via resorcinol was prepared and their physical properties investigated. 3‐{6‐[4‐(4‐Cyanophenyl)phenyl]hexyloxy}‐1‐{6‐[4‐(5‐octylpyrimidine‐2‐yl)phenyl]hexyloxy}benzene, compound I‐(6,6), was found to show monotropic nematic, smectic A and anticlinic smectic C (SmCanti) phases. We investigated the effects of the spacer length and the linking group on the phase transition behaviour. In addition, trimers with identical mesogenic units were prepared and their physical properties compared with those containing two different mesogens. Only the meta ‐substituted trimers showed the SmCanti phase despite its reduced tendency to exhibit liquid crystallinity than the ortho ‐ and para ‐substituted trimers. [ABSTRACT FROM AUTHOR]

The article addresses the role of surfactant headgroup structure on hybrid surfactant performance for water-in-CO 2 (w/c) microemulsion stabilization. The synthetic procedure, aqueous properties, and phase behaviour of a new hybrid sulfoglutarate surfactant are described. The sulfoglutarate version has an extra methylene group incorporated into the hydrophilic headgroup. The related hydrocarbon (AOT14 and AOT14GLU) and fluorocarbon (di-CF2 and di-CF2GLU) surfactants were used to form w/c microemulsions. For these two groups, the aqueous properties and w/c phase stability of both sulfoglutarates and sulfosuccinates were found to be similar. The newly synthesized hybrid CF2/AOT14GLU (sodium (4 H, 4 H, 5 H, 5 H, 5 H -pentafluoropentyl-2,2-dimethyl-1-propyl)-2-sulfoglutarate) proved to be more efficient than the normal sulfosuccinate, hybrid CF2/AOT14 in terms of the aqueous behaviour and w/c phase stability. Hybrid CF2/AOT14GLU more effectively decreased the air-water surface tension by ∼2 mN m −1 and lowering the cloud pressures on CO 2 by ∼150 bar. [ABSTRACT FROM AUTHOR]

This study reports unusual behaviorof aqueous-phase lamellar aggregateswith a new class of hybrid surfactant, CB-B2ES, having mesogenic units{6-[4-(4-cyanophenyl)phenyloxy]hexyl} and temperature-sensitive oxyethylated(butoxyethoxyethyl) tails. These tails are poorly miscible and likelyto microsegregate if the surfactant molecules assemble. Lamellar aggregatesappear at CB-B2ES concentrations higher than 5 wt % and were foundto undergo repeat formation/breakdown periodically at 30 °C,with an average domain lifetime of ∼10 s. To investigate effectsof the temperature-sensitive oxyethylene units on the hydrophilic/lipophilicbalance (HLB) of the CB-B2ES bilayers, a fluorescence probe 1-pyrene-carboxaldehidewas solubilized in the mixtures to sense the micro-environmental polarities.Fluorimetric measurements suggested that the polarity of CB-B2ES bilayersis very similar to that of the non-ethoxylated CB-B2ES analogue athigh temperatures (≥65 °C). However, for CB-B2ES, polarityincreased with a decreasing temperature, in contrast with the smalldecrease in polarity observed for analogous non-ethoxylated bilayers.This is consistent with increased hydration of the oxyethylene unitsin CB-B2ES bilayers at low temperatures. The periodic formation/breakdownand cooling-induced hydrophilicity of the CB-B2ES lamellar aggregatesdid not appear in the non-hybrid and/or non-ethoxylated surfactantsystems. Therefore, the combination of two unsymmetrical tails, onecontaining oxyethylene units and the other containing cyanobiphenylterminal tips, must play an important role promoting this unusualbehavior. [ABSTRACT FROM AUTHOR]

The relationship between the tail architecture and performance of hybrid AOT analogue surfactants has been investigated. Three hybrid surfactants were synthesised using hydrocarbon CO 2 -philic tails with different levels of chain branching. The performance of each surfactant was investigated via high-pressure phase behaviour, UV-visible spectroscopy, and air–water (a/w) surface tension measurements. Notably, the incorporation of hydrocarbon CO 2 -philic tails with a high degree of branching has been found to significantly boost CO 2 -philicity, allowing the surfactant to stabilise water-in-CO 2 (w/c) microemulsions at low cloud pressures, P trans . The newly synthesised hybrid CF2/SIS1 (sodium ( 4H, 4H, 5H, 5H, 5H -pentafluoropenyl-5,7,7-trimethyl-2-(1,3,3-trimethyl-buthyl)-octyl)-2-sulfosuccinate) is a CO 2 -philic surfactant that contains the lowest amount of fluorine (15.01 wt%) and exhibits the highest efficiency of any di-chain surfactant to date. High-pressure phase behaviour studies provided a maximum water-to-surfactant molar ratio ( w max ) of w max = 39, which is usually only observed from surfactants with long fluorocarbon chains. The present results are beneficial for expanding the pool of economical, effective, and efficient surfactants available for CO 2 -based technology. [ABSTRACT FROM AUTHOR]

Previous studies [Langmuir, 2014, 30, 21, 6057–6063, Phys. Chem. Chem. Phys., 2017,19, 23869–23877] have shown that surfactants bearing highly-methylated alkyl tails (so-called "hedgehog" groups) are able to reduce the limiting surface tension at the aqueous critical micelle concentration (CMC) to γ CMC ~24 mN m−1, which is considerably lower than for common n -alkyl tail surfactants (30–40 mN m−1). In the quest to develop even more effective and efficient non-fluorinated surfactants, this study introduces new amphiphiles having double and triple hedgehog tails and examines relationships between surfactant structure and aqueous solution properties. Of particular interest are links between γ CMC , the effective hydrophobic-tail layer density (ρ layer) and total number of carbon and silicon atoms in the hydrophobic tails (N C+Si). Interestingly, γ CMC is seen to depend on ρ layer rather than N C+Si , and ρ layer ~0.63 g cm−3 appears to be an optimal surface layer density for promoting low γ CMC. For a surfactant bearing trimethysilyl (TMS) chain tips, exchanging the surfactant counterions from Na+ to Mg2+ reduced γ CMC from 23.8 mN m−1 to 21.5 mN m−1, which is very low for a hydrocarbon surfactant, and comparable to typical fluorinated surfactants. A new measure of the ability of different surfactants to lower surface tension is proposed, which is helpful for targeting low surface energy (tension) non-fluorinated surfactants. In terms of both γ CMC and CMC TMS-terminal tips are shown to be key groups for promoting hydrophobicity and/or low surface tensions. [Display omitted] • Highly-methyl-branched-tail (hedgehog) surfactants were synthesized and evaluated. • Surfactants with Mg2+ and TMS tips attained aqueous surface tensions of ~21.5 mN m−1. • Low surface tensions were achieved with apparent hydrophobic layer densities of ~0.63 g cm−3. • TMS tips resulted in larger hydrophobicity and/or surface tension reducing ability per CH 2 unit. [ABSTRACT FROM AUTHOR]