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The micellar and morphological properties of symmetric, cationic gemini surfactants have been well studied in the literature as a function of nature and type of the spacer group and the length and type of hydrophobic chain. In this paper, we have examined the effects of tail asymmetry on the properties of a series of cationic surfactants, the N-alkyl-1-N'-alkyl-2-N,N,N',N'-tetramethyldiammonium dibromide. A novel synthetic method is used to prepare a series of these surfactants and the consequences of asymmetry on micellar properties are presented. This new method has been shown to be more efficient, with higher yields of the asymmetric surfactants than the yields of the accepted literature method. The critical micelle concentration values and the micelle sizes of the asymmetric gemini surfactants, 12-4-12, 12-4-10, 12-4-8, and 12-4-6 gemini surfactants, were obtained from conductivity and dynamic light scattering. With increasing chain asymmetry, the size of the micelle increased due to the formation of loose micelles. The addition of NaCl and N[a.sub.2]S[O.sub.4] to the surfactant solutions increased the aggregate size, and this effect was more pronounced with increasing salt concentrations. These results are interpreted in terms of the effect these ions have on the 'compactness' of the micelle structure. Key words: micelles, light scattering, critical micelle concentration, morphology, gemini surfactants. Les proprietes micellaires et morphologiques des tensioactifs gemines cationiques symetriques sont bien decrites dans la litterature comme une fonction de la nature et du type du groupe espaceur, et de la longueur et du type de la chaine hydrophobe. Dans le present article, nous avons examine les effets de l'asymetrie de la queue sur les proprietes d'une serie de surfactants cationiques, les dibromures de N-alkyl-1-N'-alkyl-2-N,N,N',N'-tetramethyldiammonium. Nous avons employe une nouvelle methode de synthese pour preparer une serie de ces surfactants et nous presentons les effets de l'asymetrie sur leurs proprietes micellaires. Cette nouvelle methode s'est revelee plus efficace, produisant les surfactants asymetriques en rendements plus eleves comparativement a la methode acceptee dans la litterature. Nous avons mesure la concentration micellaire critique et la taille des micelles des tensioactifs gemines asymetriques 12-4-12, 12-4-10, 12-4-8 et 12-4-6 a partir de la conductivite et de la dispersion dynamique de la lumiere. Plus l'asymetrie de la chaine est elevee, plus la taille des micelles formees est grande, en raison de leur structure moins compacte. L'ajout de NaCl et de N[a.sub.2]S[O.sub.4] aux solutions de surfactant a entraine une augmentation de la taille des agregats, et cet effet etait plus marque aux concentrations de sels plus elevees. Nous interpretons ces resultats sous l'angle de l'effet de ces ions sur la << compacite >> de la structure des micelles. [Traduit par la Redaction] Mots-cles : micelles, diffusion de la lumiere, concentration micellaire critique, morphologie, tensioactifs gemines., Introduction Surface active agents, more commonly known as surfactants, are compounds that have a variety of industrial and household applications. The general structure of a surfactant molecule is that of [...]

The surface and self-assembly properties of a family of multiheaded, multitailed surfactants based on a tripentaerythritol backbone are described. Critical aggregation concentrations of these unusual surfactant systems have been determined from surface tension measurements; aggregate sizes in the presence and absence of a small amount of added electrolyte have been obtained via dynamic light scattering, and the morphologies of the aggregates were examined from electron microscopy measurements. In general, when compared to conventional ionic and two-headed surfactants (and other recently synthesized pentaerythritol derived surfactants from this group), these multiheaded surfactants exhibited some unusual trends in their aggregation behaviour and interesting aggregate structures in aqueous solution, as a function of alkyl chain length. Key words: tripentaerythritol, surfactants, aggregates, critical aggregation concentration, light scattering. Le present article decrit la surface et les proprietes d'auto-assemblage d'une famille de surfactants a tetes et queues multiples, formes d'une chaine principale de tripentaerythritol. Les concentrations d'agregation critique de ces types de surfactant inhabituels ont ete determinees a partir des mesures de tension superficielle. La taille des agregats en presence ou en absence de petites quantites d'electrolytes ajoutes a ete mesuree par diffusion dynamique de la lumiere et leur morphologie a ete analysee a l'aide de mesures au microscope electronique. D'une maniere generale, lorsqu'on les compare aux surfactants habituels ioniques ou a deux tetes (ou a d'autres surfactants recemment synthetises, derives du pentaerythritol et issus de ce meme groupe), on constate que ces surfactants a tetes multiples donnent lieu a quelques phenomenes d'agregation inhabituels et a la formation de structures d'agregats interessantes en solution aqueuse, qui dependent de la longueur de la chaine alkyle. [Traduit par la Redaction] Mots-cles: tripentaerythritol, surfactants, agregats, concentration d'agregation critique, diffusion de la lumiere., Introduction We have recently described the extremely flexible synthesis of cationic, (1-3) zwitterionic, and anionic (4) two-headed surfactants based on the pentaerythritol moiety. In previous publications, these compounds have been [...]

Efficient syntheses of three series of anionic gemini surfactants based on pentaerythritol are described. A series of disulfates was prepared by the double displacement of the two cyclic sulfates in the S4-symmetric compound pentaerythritol spirobicyclic sulfate (1) with linear alkoxides. A second series of disulfates was prepared by reaction of the dialkoxides of di-O-alkylpentaerythritols with ethylene sulfate. The di-O-alkylpentaerythritols can be prepared as previously reported by us or by the acid-catalyzed hydrolysis of the first series of disulfates. A series of disulfonates was prepared by reaction of the dialkoxides of di-O-alkylpentaerythritols with 1,3-propanesultone. This last set of reactions was complicated by the formation of oxetanes, which probably arose from initial reversible displacement on sulfur of the sultone alkoxide by the pentaerythritol alkoxide followed by a second intramolecular displacement of the resulting sulfonate. Changing the order of addition to keep the reaction medium from containing excess base as well as lowering the reaction temperature minimized the amounts of these byproducts. All three series had excellent surfactant properties. Key words: gemini surfactants, anionic surfactants, pentaerythritol, cyclic sulfates, disulfates, sulfonates, 1,3- propanesultone. On decrit les syntheses efficaces de trois series de tensioactifs gemines anioniques a partir de pentaerythritol. Une serie de disulfates a ete preparee par double deplacement de deux sulfates cycliques dans le compose de symetrie S4 sulfate spirobicyclique de pentaerythritol (1) par des alkoxydes lineaires. Une deuxieme serie de disulfates a ete obtenue par reaction des dialkoxydes de di-O-alkylpentaerythritols avec du sulfate d'ethylene. Les di-O-alkylpentaerythritols peuvent etre prepares comme nous l'avons decrit anterieurement ou par hydrolyse de la premiere serie de disulfates catalysee par un acide. Une serie de disulfonates a ete preparee par reaction des dialkoxydes de di-O-alkylpentaerythritols avec la 1,3-propanesultone. Ce dernier ensemble de reactions a ete complique par la formation d'oxetanes qui ont probablement ete produits par le deplacement reversible initial du soufre de l'alkoxyde de sultone par l'alkoxyde de pentaerythritol, suivi par un deuxieme deplacement intramoleculaire du sulfonate resultant. La modification de l'ordre d'addition afin d'eviter que le milieu de reaction ne contienne un exces de base, de meme que la reduction de la temperature de reaction ont minimise les quantites de ces sous- produits. Les series ont toutes les trois d'excellentes proprietes tensioactives. [Traduit par la Redaction] Mots-cles: tensioactifs gemines, tensioactifs anioniques, pentaerythritol, sulfates cycliques, disulfates, sulfonates, 1,3-propanesultone., Introduction Gemini surfactants display critical micellization concentrations that are one to two orders of magnitude lower than those of the corresponding conventional surfactants with only a single head group and [...]

The nature and strength of the interactions between the 1,3-bis(dimethylhexadecyl)propanediammonium dibromide (16-3-16) gemini surfactant and a homologous series of nonionic polyoxyethylene (20) sorbitan ester surfactants having laurate (Tween 20), stearate (Tween 60), or oleate (Tween 80) alkyl tails has been investigated. The critical micelle concentration (cmc) values of the mixed gemini-tween systems were determined using the du Notly ring surface tension method, and the results have been analyzed using Clint's, Rubingh's, Motomura's, and Maeda's theories for mixed micellar systems. The results demonstrate a synergistic mixing behaviour between the Tween surfactants and the 16-3-16 gemini surfactant, where the strength of interaction is dependent upon the chain length and saturation of the Tween alkyl tail. Key words: gemini surfactants, Tween surfactants, mixed micelles, surface tension. On a etudie la nature et la force des interactions entre l'agent de surface jumeau dibromure de 1,3- bis(dimethylhexadecyl)propanediammonium (16-3-16) et une serie d'agents de surface non ioniques a base d'ester de polyoxyethylene (20) sorbitane comportant des chaines alkyles du laurate (Tween 20), du stearate (Tween 60) ou oleate (Tween 80). On a determine; les valeurs de concentration micellaire critique (cmc) des systemes mixtes jumeau-Tween en faisant appel a la methode de la tension superficielle des anneaux de Noiiy et on a analyse les resultats a l'aide des theories de Clint, de Rubingh, de Motomura et de Maeda pour les systemes micellaires mixtes. Les resultats mettent en evidence un comportement de melange synergistique entre les agents de surface de la famille Tween et l'agent de surface jumeau 16-3-16 et la force de l'interaction depend de la longueur et de la saturation de la chaine alkyle du Tween. Mots-cles: agents de surface jumeaux, agents de surface Tween, micelles mixtes, tension superficielle. [Traduit par la Redaction], Introduction Gemini surfactants represent an intriguing class of surfactants that have been extensively studied by various research groups since the late 1980s. Their unique structure, which consists of two typical [...]

Proton chemical shifts and two-dimensional COSY and NOE spectroscopy (NOESY) experiments have been used to examine the interaction of various oppositely charged surfactant and poly electrolyte systems, namely, the cationic surfactant dodecyltrimethyammonium bromide (DTAB) and a series of alkanediyl-α,ω-bis(alkyldimethyl ammonium bromide) surfactants (Gem 12-s-12, where .v is the length of the methylene spacer group) with the anionic poly electrolyte poly(styrene sulfonate) or PSS. In all cases, we observe substantial aromatic-so lute-induced chemical shifts (ASIS) in the surfactant peaks of the polymer/surfactant complexes versus that of the pure surfactant spectra. In the case of the DTAB/PSS system, the chemical-shift changes as a function of changing ratio of surfactant to polymer are interpreted in terms of structural changes that occur in the complex with increasing polymer concentration. For the Gem 12-s-12/PSS systems, the interaction of these gemini surfactants with the anionic polyelectrolyte, as deduced from the interpretation of the ¹H ASIS shifts and the NOESY cross peaks, is dependent on the length of the methylene spacer. From the NOESY experiments, we observed significant NOESY cross peaks that correlated well with the expected mechanism of interaction as observed in the literature for the single-tailed surfactant/polymer system. NMR techniques are shown to provide information on the molecular arrangement of these molecules in aqueous solution. Key words: polymers, surfactants, complexes, ASIS experiments, 2D NOESY. Resume : On a fait appel a des experiences deplacements chimiques du proton et de spectroscopic de correlation Bidimensionnelle (<< COSY >>) et de spectroscopic d'effets Overhauser nucleaire (NEOSY) pour etudier l'interaction entre divers systemes formes d'un agent de surface et de poly electrolytes de charges opposes, en particulier de micelles cationiques de l'agent de surface dodecyltrimethylammonium (DTAB) et une serie de bromures d'alcanediylα, ω-bis(alkyldimethylammonium) (Gem 12-s-12 dans lesquels s correspond a la longueur du groupe espaceur methylene) avec le polyelectrolyte anionique sulfonate de poly(styrene), SPS. Dans tous les cas, on observe d'importants deplacements anisotropiques induits parle solvant (DAIS) dans les pics des complexes polymere/agent de surface par rapport aux spectres de l'agent de surface pur. Dans le cas du systeme DTAB/SPS, les changements dans le deplacement chimique en fonction d'un changement dans le rapport d'agent de surface au polymere sont interpretes en fonction de changements strueturaux qui se produisent dans le complexe avec une augmentation dans la concentration du polymere. Pour les systemes Gem 12-s-12/SPS, l'interaction entre ces agents de surface jumeaux avec le polyelectrolyte anionique, telle que deduile de 1'interpretation des deplacements anisotropiques induits par le solvant pour le ¹H et des croisements de pics (NEOSY), est dependante de la longueur de l'espaceur methylene. A partir des experiences (NEOSY), on a observe des croisements de pics (NEOSY) importants qui donnent une bonne correlation avec le mecanisme attendu d'interaction tel qu'observe dans la litterature pour le seul systeme agent de surface polymere etudie. On a done demontre que les techniques de la RMN peuvent fournir de l'information relative a l'arrangement moleculaire de ces molecules dans une solution aqueuse. Mots-cles : polymeres, agents de surface, complexes, deplacements anisotropiques induits par le solvant (DAIS), spectroscopic d'effets Overhauser nucleaire bidimensionnelle (NEOSY). [Traduit par la Redaction] doi:10.1139/V09-039, Introduction The interaction of polymers and surfactants has received a substantial amount of attention in the literature from both an academic and an industrial standpoint. (1-28) The manner in which [...]

Weakly interacting ligands including three Gemini surfactants, didodecyldimethylammonium bromide (DDAB), and amines ([RNH.sub.2], [R.sub.2]NH, and [R.sub.3]N) were used to prepare Au nanoparticles (NPs). Aqueous Au NPs capped with DDAB and Gemini surfactants showed similar sizes (3-4 nm), whereas toluene-based NPs stabilized with DDAB, amines, and their mixtures range from 2.5 to 9.3 nm. Ligand effect on Au-Pd NP structure was also studied with EXAFS. These findings were consistently accounted for by considering the ligand's electronic/steric effects and mixed ligands coadsorption, and suggest useful ways to control NP structure by manipulating the two effects and using mixed capping ligands. Key words: metal nanoparticles, capping ligands, electronic effect, steric effect, EXAFS. On a utilise des ligands interagissant faiblement, dont trois agents de surface Gemini, le bromure de didodecyldimethylammonium (BDDA) et des amines ([RNH.sub.2]), [R.sub.2]NH et [R.sub.3]N) pour preparer des nanoparticules (NP) d'or (Au). Les tailles des nanoparticules d'or aqueuses, fermees avec du BDDA ou des agents de surfaces Gemini sont assez semblables (3-4 nm) alors que celles des nanoparticules a base de toluene et stabilisees par du BDDA, des amines ou leurs melanges varient de 2,5 a 9,3 nm. On a aussi examine l'effet de ligand sur la structure des nanoparticules Au--Pd par la technique de structure fine d'absorption des rayons-X etendue (SFAXE). Les observations peuvent etre expliquees d'une facon coherente en considerant les effets sterique/electronique du ligand et la coadsorption des ligands mixtes et ceci suggere des facons utiles de controler la structure des nanoparticules en manipulant les deux effets et en utilisant des ligands mixtes pour les fermer. Mots-cles : nanoparticules metalliques, ligands de fermeture, effet electronique, effet sterique, structure fine d'absorption des rayons X etendue (SFAXE). [Traduit par la Redaction], Introduction Selection of capping ligands for the synthesis of metal nanoparticles (NPs) is of fundamental and technological importance. (1-6) Capping the NP surface with alkanethiols and their derivatives has become [...]

Abstract: The micellization process of sodium 8-phenyloctanoate in a deuterated aqueous solution was studied, using ¹H NMR spectroscopy and two-dimensional (2D) nuclear Overhauser enhancement spectroscopy (NOESY). ¹H NMR spectra, acquired [...]

The micelle formation process for a zwitterionic surfactant, N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (ZW3-12), has been investigated in a series of mixed solvents consisting of different concentrations of ethoxylated alcohols and polymers. The critical micelle concentrations (cmc values) of the aggregates were determined by fluorescence spectroscopy, and the surfactant aggregation numbers were obtained from luminescence probing experiments. The cmc values for ZW3-12 changed very little in the presence of increasing amounts of poly(ethyleneoxide) (PEO) in the mixed solvent. In the case of the ethoxylated alcohol--ZW3-12 systems, the cmc values and aggregation numbers decreased systematically with increasing alcohol concentration. However, the cmc values of the mixed micelles showed little dependence on the number of ethylene oxide (EO) groups at constant alcohol concentration. These results are compared with the well-studied sodium dodecylsulfate--ethoxylated alcohol, and dodecyltrimethylammonium bromide--ethoxylated alcohol mixed micellar systems and to SDS-PEO systems and are discussed in terms of the contribution of the EO groups to the hydrophobic interactions. Key words: zwitterionic surfactant, alcohols, mixed micelles, luminescence probing. On a etudie le processus de formation de micelle pour un agent de surface zwitterionique, le N-dodecyl-N,N-dimethyl-3-ammonio-l-propanesulfonate (ZW3-12), dans une serie de solvants mixtes formes de concentrations diverses d'alcools ethoxylEs et de polymeres. On a detennine les concentrations micellaires critiques (valeurs des cmc) en faisant appel a la spectroscopie de fluorescence et on a obtenu les nombres d'agregation de l'agent de surface a partir d'experiences de luminescence exploratoire. Les valeurs de cmc pour le ZW3-12 varient tres peu en presence de quantites croissantes de poly(oxyde d'ethylene) (POE), dans le solvant mixte. Dans le cas des systemes alcool ethoxyle--ZW3-12, les valeurs des cmc et les nombres d'agregation diminuent d'une facon systematique avec une augmentation de la concentration d'alcool. Toutefois, les valeurs des cme ne dependent que faiblement sur le nombre de groupes d'oxyde d'ethylene (OE), a des concentrations constantes d'alcool. Ces resultats se comparent bien avec les systemes micellaires mixtes bien etudids dodecylsulfate de sodium--alcool ethoxyle et bromure de dodecyltrimethylammonium--alcool ethoxyle et aux systemes SDS-POE et on les discute en fonction de la contribution des groupes OE aux interactions hydrophobes. Mots cles : agent de surface zwitterionique, alcool, micelles mixtes, luminescence exploratoire. [Traduit par la Redaction]

Introduction: The definition of a molecular diagnosis for patients affected by hereditary hearing loss (HHL) is significantly hampered by the extreme clinical and genetic heterogeneity that characterise the condition. In particular, peculiar and understudied cases are those of non-syndromic mimics (NSM), meaning patients with particularly mild forms of syndromic HHL or initially presenting isolated deafness and delayed onset of other clinical signs. Material and methods: In the last 18 months, a cohort of 73 apparently non-syndromic Italian HHL patients has been enrolled in the study. All the individuals were negative at GJB2 and STRC genetic tests and underwent whole-exome sequencing, aiming to define a molecular diagnosis and eventually identify NSMs. Results: A molecular diagnosis was provided for 36/73 patients (49.3%), and 12 of them could be classified as NSMs. In detail, two groups of patients could be highlighted: (1) patients presenting subtle additional signs that were missed during the first clinical evaluation and (2) patients whose molecular diagnosis suggests the future development of additional clinical features. In Group 1, two patients were identified, and they carried pathogenic variants within the MITF and GATA3 genes, which are associated with Waardenburg and Barakat syndromes, respectively. As regards Group 2, ten patients were detected, and the involved genes were CDH23 (one patient), USH2A (six patients) and ADGRV1 (three patients). Thus, these results suggest that Usher syndrome type 2 accounts for the vast majority of NSMs (75%). Moreover, these considerations further confirm our previous findings regarding the high prevalence of Usher syndrome type 2 carriers in the Italian population (1: 70). Conclusions: Identifying patients within Group 1 of NSMs highlights the importance of a critical re-evaluation of the diagnostic criteria of each condition and provides crucial insight into the clinical characteristics of very mild forms of syndromic deafness. On the other hand, the clinical condition of Group 2 NSM patients will be evaluated by a multi-disciplinary team in order to provide personalised follow-up and specific preventive strategies. [ABSTRACT FROM AUTHOR]

The micellization and the thermodynamic properties of a series of sodium cyclohexyl alkanoates of the general formula [C.sub.6][H.sub.11][(C[H.sub.2]).sub.n]COONa (where n = 1, 2, 3, 4) were investigated employing conductivity, density, surface tension, viscosity, speed of sound, luminescence probing experiments, and Fourier transform infrared (FT-IR) spectroscopy. The critical micelle concentrations (cmcs) and the aggregation numbers indicate that these surfactants have high cmc values and low aggregation numbers when compared to other single-headed surfactants (most notably the sodium alkanoates). Thermodynamic properties, obtained from the mass action model, indicate that micellization is spontaneous and entropically driven. The saturation area per molecule, the free energies of adsorption, and the efficiency and effectiveness of adsorption were determined through surface tension measurements. The presence of the cylcohexyl ring appears to influence the surface properties of micellization. Both the effectiveness and the efficiency of these surfactants, in lowering the surface tension of water, are lower than that of the straight chain alkanoates. Key words: thermodynamics, micellization, aggregation numbers, speed of sound, and spectroscopy.