Mesomorphic-like character of long-chain amine salts formed by template neutralization on polyacids

Several examples of monomeric and polymerized surfactants exhibiting liquid-crystalline behaviour have recently been reported. In the present investigation a novel process for the formation of liquid crystals is introduced, according to which certain functionalized polymers induce mesomorphism when they react with appropriate amines. For instance, neutralization of polyacrylic or polymaleic acid with long-chain amines forms alkylammonium salt surfactants which exhibit mesomorphic-like character. In this type of experiment, however, the known lamellar structure of alkylammonium salts was modified by this so-called template neutralization. The carboxylate groups, due to their location on the polymeric chain, appear to exert a topochemical effect on alkylammonium moieties which in turn affect the mesomorphic behaviour compared with that of common surfactants. The mesomorphic behaviour of these materials was established by optical microscopy and differential scanning calorimetry.     

Synthesis and physico-analytical studies of some novel ferrocenyl Schiff base derivatives

A series of ferrocenyl Schiff base derivatives was synthesized by condensation reactions of 1,1′-ferrocenedicarboxaldehyde and aromatic amines containing long chain alkyl groups as free ends which were characterized by their physical properties, elemental, FTIR, ¹H NMR, ¹³C NMR spectral and thermal analysis. The thermal behaviour of the synthesized compounds was studied by differential scanning calorimetry (DSC) which revealed that these compounds may exhibit mesomorphic properties. The DSC results of aromatic amines and ferrocenyl Schiff bases were compared to study the effects of structure, i.e. rigid core and terminal chain length, on the phase transition behaviour.     

The effect of hydrogen bonding, molecular shape, dipole moments, and chain length on the mesomorphism of some D-glucose and D-glucosamine derivatives

Diverse 4-substituted-benzyl 1-O-alpha- and beta-D-glucopyranosides, 4-substituted-benzyl 2-deoxy2-trifluoroacetamido-alpha- and beta-D-glucopyranosides and 4-substituted-benzyl 2-acetamido2-deoxy-alpha- and beta-D-glucopyranosides have been synthesized. They were prepared directly by a one-step alkylation of commercially available carbohydrate starting materials. The 4-substituted-benzyl 2-deoxy-2-trifluoroacetamido-alpha- and beta-D-glucopyranosides were cleaved to yield the corresponding free amines. The influence of hydrogen bonding, terminal dipole moments, molecular shape and chain length on the thermotropic mesomorphic behaviour of these benzyl-substituted carbohydrate amphiphiles is discussed. Comparisons between the mesomorphic behaviour of the new benzyl-substituted carbohydrates and that of the related phenyl-substituted carbohydrates, as well as the non-aromatic n-alkyl D-glucosides, are made. Although the new carbohydrates do not exhibit lyotropic phase behaviour, the 4-substitutedbenzyl 2-deoxy-2-trifluoroacetamido-alpha- and beta-D-glucopyranosides have been found to gel water at very low sugar concentrations.     

Polymerization of head and tail methacrylate micelle-forming surfactants and thermotropic liquid-crystalline character of these monomers and their polymers

The polymerization in micellar and isotropic media of a head-tail pair of surfactants, i.e. of monomers bearing the methacrylate group either at the polar head or at the end of the lipophilic chain is investigated in this study. Owing to the tailor-made structure of these monomers, any differentiations observed in their polymerization can be primarily attributed to topochemical effects resulting from the different location of the polymerizable group in the two monomers. Both monomers exhibited mesomorphic-like textures, which were examined by optical microscopy and DSC studies. Also, their respective polymers showed mesomorphic behaviour, which was found to be dependent on the position of the backbone relative to the polar head.     

Polymerization of head and tail methacrylate micelle-forming surfactants and thermotropic liquid-crystalline character of these monomers and their polymers

The polymerization in micellar and isotropic media of a head-tail pair of surfactants, i.e. of monomers bearing the methacrylate group either at the polar head or at the end of the lipophilic chain is investigated in this study. Owing to the tailor-made structure of these monomers, any differentiations observed in their polymerization can be primarily attributed to topochemical effects resulting from the different location of the polymerizable group in the two monomers. Both monomers exhibited mesomorphic-like textures, which were examined by optical microscopy and DSC studies. Also, their respective polymers showed mesomorphic behaviour, which was found to be dependent on the position of the backbone relative to the polar head.     

易水解类表面活性剂的表面与胶团性质

对直链烷基羧酸盐与烷基氯化伯铵两类易水解型表面活性剂进行了较系统的研究,发现pH 值、温度、 盐浓度的变化对体系表面性质及胶团形成有较明显的影响.二类体系中相应水解产物的存在均可较大幅度地提高体系的表面活性,但pH 值在碱性范围内的变化仍对羧酸钠的表面性质与胶团形成有明显影响,而烷基氯化铵的表面性质与聚集能力在酸性条件下则主要受盐浓度的影响,而不受pH 值影响.表明这两类易水解体系产生的极性有机物对各自体系的表面性质和聚集能力影响力度不同.考察了温度对易水解类表面活性剂的影响,并利用相分离模型对相应体系的胶团形成热力学参数进行了计算与讨论.     

Geminal alkylammonium surfactants: Aggregation properties and catalytic activity

Geminal alkylammonium surfactants containing a hexamethylene spacer show a specific behavior, namely, a catalytic effect at low concentrations of the detergent in the system. The critical micellization concentrations of these surfactants are by an order of magnitude lower than those of the related surfactants with one hydrophobic fragment. The effect exerted on the hydrolysis of carboxylic acid esters by micellar structural rearrangements induced by addition of a supporting electrolyte is determined.     

Ionic Liquid Crystals Formed by Self‐Assembly around an Anionic Anthracene Core

We have designed and synthesised a series of modular, mesogenic complexes based on anthracene‐2,6‐disulfonate and trialkoxybenzyl‐functionalised imidazolium cations. Each complex contains a central, rigid, dianionic anthracene core and two flexible monocations bearing paraffin chains anchored on imidazolium rings. Anthracene‐2,6‐disulfonate can be crystallised with various simple alkylammonium ions and, in the case of ⁺N(CH₃)₂(C₁₆H₃₃)₂, a crystal structure determination has shown that the long paraffinic chains are intercalated between the anthracene moieties. The dianion forms columnar mesophases with trialkoxybenzylimidazolium cations, as identified by polarising optical microscopy and X‐ray scattering measurements. Differential scanning calorimetry studies confirmed mesomorphic behaviour from room temperature to about 200 °C for alkyl chains containing 8, 12 and 16 carbon atoms. The strong luminescence of anthracene is maintained in the mesophase and fluorescence measurements confirmed the presence of J aggregates in all cases. The new functional materials described herein provide an easy access to stable and luminescent mesomorphic materials engineered by an ionic self‐assembly process.     

Critical micelle concentrations and interaction parameters of aqueous binary surfactant:ionic surfactant mixtures

A relationship between the critical micelle concentration (CMC) and the surfactant's composition in the bulk phase that supercedes Rubingh's method is derived for aqueous mixtures of ionic surfactants by considering the interaction between a micellar ionic aggregate and the diffusion layer around it. To test this approach we measured the CMCs of solutions of cationic surfactant mixtures and also of alkylammonium dodecanesulfonate mixtures. In the absence of controlled concentration of the counterion, the CMCs do not fit Clint's equation, but CMCs measured at a constant counterion concentration fit it approximately. The interaction parameter in the theory of regular solutions is obtained from the relationship between the micellar and bulk compositions. The values of the interaction parameter and the concentration exponent change with the hydrophobicity of the counterion in mixtures of alkylammonium dodecanesulfonates. The micellar composition of dodecylammonium chloride and dodecyltrimethylammonium chloride mixtures depends very little on the counterion concentration. The interaction energy between the ammonium and trimethylammonium groups of the cationic surfactants is about -0.05kT on average and depends on the concentration of the counterion.     

Synthesis and mesomorphic properties of perfluorinated rod-like liquid crystals with sulphur-containing spacers

In order to determine the influence of 'sulphur-containing' spacers on the formation of mesophases in low molecular mass compounds, we have examined the mesomorphic behaviour of molecules which consists of a 4-biphenyl unit linked to an unbranched fluorinated chain via a short spacer including at least a sulphur atom. The synthesis of these compounds has been carried out from 2-F-butylethyl iodide or from the 2-F-alkylethyl mercaptans in the case of the F-hexyl and F-octyl tails. The mesomorphic properties have been characterized by polarized light microscopy and by differential thermal analysis showing the peculiar contribution of each of the spacers. The influence of the fluorinated chain and the shape of the connector on the stability of the mesophases has been investigated. The compounds with a thioether or a hemithioacetal spacer showed no mesomorphic properties, whereas the structures with a thioester spacer showed a very interesting enantiotropic behaviour of the smectic A type over a wide temperature range. Furthermore from the series exhibiting liquid crystalline behaviour, increasing the number of fluoromethylene units simultaneously increases both the melting and the clearing temperature. These mesomorphic properties within the fluorinated series are compared with those of their monocatenar hydrocarbon homologues.     

Synthesis and mesomorphic properties of perfluorinated rod-like liquid crystals with sulphur-containing spacers

In order to determine the influence of 'sulphur-containing' spacers on the formation of mesophases in low molecular mass compounds, we have examined the mesomorphic behaviour of molecules which consists of a 4-biphenyl unit linked to an unbranched fluorinated chain via a short spacer including at least a sulphur atom. The synthesis of these compounds has been carried out from 2-F-butylethyl iodide or from the 2-F-alkylethyl mercaptans in the case of the F-hexyl and F-octyl tails. The mesomorphic properties have been characterized by polarized light microscopy and by differential thermal analysis showing the peculiar contribution of each of the spacers. The influence of the fluorinated chain and the shape of the connector on the stability of the mesophases has been investigated. The compounds with a thioether or a hemithioacetal spacer showed no mesomorphic properties, whereas the structures with a thioester spacer showed a very interesting enantiotropic behaviour of the smectic A type over a wide temperature range. Furthermore from the series exhibiting liquid crystalline behaviour, increasing the number of fluoromethylene units simultaneously increases both the melting and the clearing temperature. These mesomorphic properties within the fluorinated series are compared with those of their monocatenar hydrocarbon homologues.     

Response and selectivity characteristics of alkylammonium ion-selective electrodes

A series of poly(vinyl chloride) matrix coated-wire electrodes based on dinonylnaph-thalene sulfonic acid (DNNS) selective to various alkylammonium ions was prepared and selectivity characteristics were evaluated. A set of tributylammonium electrodes was used to study the interference by a homologous series of alkylammonium ions. Selectivity coefficient (k^pot_i,j) values for alkylammonium ions at a given carbon number decreased in the order primary, secondary, tertiary, quaternary. A linear increase in log k^pot_i,j with carbon number was observed in each series. Two additional sets of electrodes selective to dodecylammonium ion and to di-n-hexylammonium ion were evaluated for response to other C-12 amines. Electrodes for primary amines showed little or no response to secondary and tertiary amines, while electrodes for tertiary amines responded strongly to primary amines and less strongly to secondary amines. The effect of structural modifications was evaluated in a study of N-substituted cydohexylamines. The dependence of the magnitude of k^pot_i,j on the concentration of the interference was determined for both strongly and weakly interfering species. For strong interferences, k^pot_i,j was observed to increase to a maximum value of characteristic concentration. For weak interferences, the k^pot_i,j variation with concentration was markedly less. Guides for estimating the response to an interfering species based on its structure and molecular weight were obtained. The results are compared to analogous solvent-extraction systems. The significance of these results is discussed in terms of quantifying different components in binary mixtures using several electrodes simultaneously.     

Widening of the elution window in micellar electrokinetic chromatography with cationic surfactants. II. Cationic additives and modifiers of the electroosmotic flow.

In micellar electrokinetic chromatography (MEKC) with cationic surfactants the migration window is significantly narrower than with anionic surfactants. In order to overcome this disadvantage of cationic surfactants, it is investigated whether it is possible to widen the migration window by reducing the velocity of the aqueous phase while the electrophoretic mobility of the micelles is maintained. Short chain alkylammonium compounds, hexamethonium bromide and hydroxypropylmethylcellulose are tested as additives to the separation electrolyte with the potential to improve the migration window via reducing the velocity of the electroosmotic flow. It will be shown that these modifiers can be successfully used in order to widen the migration window in MEKC with cationic surfactant employing an alkyltrimethylammonium bromide as micelle forming agents. Influence of the modifiers selected on retention of neutral and acidic solutes and on efficiency of the separation system is investigated.     

Interactions in Aqueous Mixtures of Alkylammonium Chlorides and Sodium Cholate

The interactions of alkylammonium chlorides (the number of carbon atom per chain was either 12, 14, or 16) with sodium cholate have been investigated by a combination of techniques including light and electron microscopy, surface tension, conductivity, light scattering, and microelectrophoretic measurements. The phase behavior has strongly depended on the molar ratio and actual concentration of oppositely charged surfactants. The change in the composition of the aggregates leads to a shape transformation from globular to elongated micelles to open and/or closed bilayers (vesicles) and precipitation. The length of micelles has been found to decrease dramatically with the concentration shift to the micellar regions of either surfactant. Upon a moderate excess of one surfactant, the mean hydrodynamic diameter of aggregates increases and wormlike micelles and/or open and closed bilayers are formed. Microscopic observations of alkylammonium cholates (novel catanionic surfactants precipitated in and/or close to equimolar region) have shown the presence of a variety of morphologies including twisted ribbons, tubules and bundles of tubules.     

New symmetric azomethinic dimer: the influence of structural heterogeneity on the liquid crystalline behaviour

The paper deals with the study of the thermotropic liquid crystalline properties of a new azomethinic symmetric dimer and some of its structural heterogeneous mixtures with one of its reagents. Their thermotropic behaviour was monitored by polarised light microscopy, differential scanning microscopy and variable temperature X-ray diffraction measurements. The influence of the structural heterogeneity on the mesomorphic behaviour was established and some similarities with the mesomorphic behaviour of the polydisperse polymers were underlined.     

Silicon-Modified Carbohydrate Surfactants III: Cationic and Anionic Compounds

Ionic siloxanyl-modified carbohydrate surfactants have been synthesized by alkylation/esterification of precursors containing tertiary amino functions. Depending on the reaction strategy, the siloxanyl moiety is part of the alkylating agent or the substrate. Polyhydroxylated tertiary amines can be quaternized by siloxanyl-modified chloroacetic acid esters or epoxysiloxanes in the presence of glacial acetic acid. The esterification of tertiary amines bearing carbohydrate and siloxanyl subunits by cyclic acid anhydrides yields, after neutralization, carboxylate salts. The reaction of hydroxyl groups and sulfamic acid leads to sulfates. The new substances were characterized by means of ¹³C NMR spectroscopy, gas chromatography, elemental analysis and their solubility profile. © 1997 John Wiley & Sons, Ltd.     

Synthesis, computational modelling and liquid crystalline properties of some [3]ferrocenophane-containing Schiff’s bases and β-aminovinylketone: Molecular geometry-phase behaviour relationship

Rotationally fixed [3]ferrocenophane extends the variety of possible molecular geometries in its derivatives in comparison with unbridged ferrocenes. In this respect molecular geometry-liquid crystalline properties relationship studies in [3]ferrocenophane mesogens are of considerable interest. Different positional isomers of mono- and di-substituted [3]ferrocenophanes which are obtained by incorporating one or two promesogenic building blocks into the cyclopentadienyl rings are reported in this article. A series of mono-substituted [3]ferrocenophane-containing Schiff’s bases was synthesized by condensing isomeric p-aminophenyl [3]ferrocenophanes with appropriate aldehydes. Isomers of di-substituted [3]ferrocenophane amines gave rise to a series of azomethines with two promesogenic substituents in the cyclopentadienyl rings. Besides, a β-enaminoketone was prepared from 3-(p-aminophenyl)[3]ferrocenophane. Nematic and smectic mesophases were observed in the synthesized compounds under a polarizing optical microscope. The [3]ferrocenophane-containing β-enaminoketone showed complex mesomorphic behaviour connected with occurrence of the keto-enamine and imino-enol tautomeric equilibrium in this compound. On the base of computational models obtained by semi-empirical quantum chemistry calculations the molecular geometry-phase behaviour relationships were examined. It was demonstrated that mesomorphism of [3]ferocenophane azomethines depends on the spatial orientation of the substituents with respect to the propanediyl bridge in a case of mono-, and as well as to each other in a case of di-substituted derivatives.     

含氧光敏聚合反应中表面活性剂的催化作用

本文研究了二苯酮/三乙胺/氧体系引发MMA的光聚合反应中烷基铵羧酸盐类(R₁R₂R₃R₄N⁺O^-OCR₅)离子型表面活性剂的催化作用。实验结果表明,聚合速度的大小和表面活性剂的类型,分子结构以及浓度有关。表面活性剂分子对系统中氢过氧化物光敏分解的促进,使聚合反应的量子产率提高了两倍多。     

Determination of Quaternary Ammonium Compounds by HPLC with a Hydrophilic Polymer Column and Conductometric Detection after Trace Enrichment by Solid Phase Extraction

Quaternary ammonium compounds containing at least one long alkyl chain act as cationic surfactants and are widely used as fabric softeners, disinfectants and human hair cosmetics. After usage, the surfactants are generally discharged via waste water treatment facilities to surface waters. Hence they can disturb the ecological balance due to their toxicity to aquatic organisms. In this context reliable analytical methods for determination of quaternary alkylammonium compounds are required in the analysis of environmental samples as well as in the quality control of manufactured products.     

Modelling the surface free energy parameters of polyurethane coats—part 2. Waterborne coats obtained from cationomer polyurethanes

Polyurethane cationomer coats were synthesised on the basis of typical diisocyanates, properly selected polyether polyols, HO-tertiary amines and HCOOH as quaternisation reagents. The values of their surface free energy (SFE) parameters were obtained by the van Oss-Good method, with the use of the contact angle values which had been found by the goniometric method. Based on the obtained findings, empirical models were developed which made it possible to anticipate the effects of the raw material types on the SFE values of the produced coats. The possibility was noted to adjust the SFE values within 25–50 mJ/m² by selecting carefully suitable parent substances. The principal consequences for the formation of improved hydrophobicity coats, applicable inter alia specialised protective coatings, were found to come not only from diisocyanate and polyol types but also from the alkylammonium cation structure which results from the use of different tertiary amines. The fundamental SFE lowering effect was noted when tertiary amines with 0–15 % of the 2,2,3,3-tetrafluoro-1,4-butanediol as a fluorinated chain extender was incorporated into polymer chains.