Glucose-based surfactants with hydrogenated, fluorinated, or hemifluorinated tails: synthesis and comparative physical-chemical characterization

(Hemi)fluorinated hydrophobic chains have been found to minimize the denaturating propensity of surfactants toward membrane proteins. The work reported herein deals with the synthesis of a new series of non-ionic glucose-based surfactants endowed with a hybrid hemifluorocarbon chain. The convergent synthesis is based on a one-pot reduction/alkylation of hemifluorinated thioacetate and glucosylated trishydroxymethyl acrylamidomethane using NaBH4 in methanol. This "mild" alkylation was studied in order to improve yields and to pass up the use of an excess of commercially unavailable hemifluorinated thiols. The physical-chemical properties in aqueous solution of this novel series were studied by surface tension measurement and dynamic light scattering (DLS), as well as their behavior upon reverse-phase chromatography, and were compared with those of their hydrogenated and perfluorinated analogues. The atypical effect of the additional ethyl tip to the fluorinated chain was demonstrated by higher critical micellar concentration values and abnormal hydrophobicities measured by reverse-phase chromatography. Moreover, according to Israelachvili's concept, DLS studies showed that surfactants bearing bulkier polar head self-assemble into small and well-defined aggregates, suggesting the formation of spherical micelles rather than the cylindrical ones usually observed with classical fluorinated surfactants.     

The Stability of the Micelle Formed by Chain Branch Surfactants and Polymer Under Salt and Shear Force: Insight from Dissipative Particle Dynamics Simulation

The influence of salt and shear force on the stability of the micelle formed by surfactants and polymer are studied using dissipative particle dynamics (DPD) simulation method. The research system mainly includes four types of surfactants with different hydrophilic/hydrophobic chain branches and two kinds of polymers with hydrophilic/hydrophobic properties, respectively. The stability of the micelle is studied based on the analyses of the density peak and root mean square (RMS) of polymer chain under different salt and shear force. The calculated results show that the density peak reduced and RMS increased for all surfactants with the salt concentration and shear force increasing, and then indicate that the micelle has a certain degree of deformation. Whereas, the surfactant chain branch has important influence on the deformation extent of the micelle. For hydrophobic polymer, surfactants containing hydrophobic chain branch (T2H2T2) are beneficial to the stability of the micelle. On the contrary, for hydrophilic polymer, the micelle formed by surfactants with stronger hydrophilic nature such as the hydrophilic groups located in the both ends of the molecule (H1T4H1) have the best salt and shear resistance. The results have certain theoretical significance and can provide theoretical support for the selection of surfactants and polymers in practical application.     

Silicon-modified carbohydrate surfactants VI: Synthesis of carbosilane,silane, polysilane and non-permethylated siloxane derivatives; the wetting behaviour of epoxy-modified precursor liquids on non-polar surfaces

The synthesis of carbohydrate surfactants bearing carbosilane, silane, polysilane and non-permethylated siloxane moieties is described. These surfactants consist of three structural elements: (1) a silicon-containing moiety, (2) a spacer and (3) a carbohydrate unit. Additionally two different types of mixed structures have been synthesized: (a) single-chained carbosilane–siloxane surfactants and (b) double-chained combinations of carbo- silanes, silanes and siloxanes. The wetting behaviour of the key intermediates, the allyl glycidyl derivatives, has been investigated by static surface tension (γ_lv, σ) and wetting tension (γ_sv−γ_sl, α) measurements on a non-polar perfluorinated surface (FEP® plate). The contact angles obtained for these pure liquids are not a linear function of the surface tension but depend on the polarity of the substructures. © 1998 John Wiley & Sons, Ltd.     

Fluorine-fluorine interactions in the solid state: an experimental and theoretical study

The solid state structures of three compounds that contain a perfluorinated chain, CF(3)(CF(2))(5)CH(2)CH(CH(3))CO(2)H, CF(3)(CF(2))(5)(CH(2))(4)(CF(2))(5)CF(3) and {CF(3)(CF(2))(5)CH(2)CH(2)}(3)P═O have been compared and a number of C-F···F-C and C-F···H-C interactions that are closer than the sum of the van der Waals radii have been identified. These interactions have been probed by a comprehensive computational chemistry investigation and the stabilizing energy between dimeric fragments was found to be 0.26-29.64 kcal/mol, depending on the type of interaction. An Atoms-in-Molecules (AIM) study has confirmed that specific C-F···F-C interactions are indeed present, and are not due simply to crystal packing. The weakly stabilizing nature of these interactions has been utilized in the physisorption of a selected number of compounds containing long chain perfluorinated ponytails onto a perfluorinated self-assembled monolayer, which has been characterized by IRRAS (Infrared Reflection Absorption Spectroscopy).     

Propyl-ended hemifluorinated surfactants: synthesis and self-assembling properties

The advantages of using hemifluorinated surfactants as an efficient alternative to detergents for manipulating membrane proteins in aqueous solution have been demonstrated in recent reports. However, the large-scale synthesis of these surfactants is still considered as a major matter and has limited their use for biochemical purposes. We report herein the synthesis of a novel series of perfluorohexane-based surfactants endowed with a short propyl hydrocarbon tip and whose polar head size is modulated by the presence of two or three glucose moieties. The synthetic route is based on the radical addition of two alkenes onto the 1,6-diiodoperfluorohexane using AIBN as a radical initiator, affording the surfactants in satisfactory overall yields. The self-assembling properties of these hemifluorinated surfactants were studied by surface tension measurements, dynamic light scattering, as well as their behavior upon reversed-phase chromatography and were compared with those of their perfluorinated analogues. Our findings strongly suggest the predominant influence of the propyl tip on both adsorption and micellization phenomena as well as on the hydrophobic character of the surfactants, whereas as previously observed, the shorter ethyl tip does not greatly affect these properties when compared to the perfluorinated analogues. Moreover, all the surfactants reported here self-assemble into small and monodisperse aggregates, a feature of crucial importance for biochemistry applications.     

Structural and electronic properties of PFOS and LiPFOS

The structural and electronic properties of perfluorinated surfactants perfluorooctane sulfonate (PFOS) and lithium perfluorooctane sulfonate (LiPFOS) have been investigated theoretically by performing semi-empirical molecular orbital theory at the level of AM1 calculations. The optimized structure and the electronic properties of the molecules are obtained.     

Synthesis and surface properties of semi-fluorinated gemini surfactants with two reactive bromo pendant groups

This paper presents a series of semi-fluorinated gemini surfactants with two bromo pendant groups. It reviews the effect of the number of methylene units in the spacer group between the two hydrophilic quaternary ammonium heads. Critical micelle concentration (cmc) and free energy of micellization (ΔG(M)(0)) of the title surfactants, in aqueous solution, have been investigated as a function of the number n of carbon atoms in the hydrocarbon spacer. We have pointed out a different behaviour as compared to Gemini hydrocarbon homologues. In the present study, when the number of methylene units (n) in the spacer increases, the cmc first decreases and reaches an optimum for (n=6), then it increases linearly from n≥6. Variations of cmc have been interpreted in terms of conformation changes of the surfactant ion and progressive penetration of the alkyl chain spacer in the micelle hydrophobic core. In this series, the increase of the hydrophobicity seems not to favour the micellisation process as expected, probably impacted by the mutual phobicity of the perfluorinated tails and the hydrocarbon spacer. A minimum is reached for a spacer with six methylene units which seems to be the optimal conformation. The free energy of micellization (ΔG(M)(0)) confirm this tendency.     

Dilution-induced spheres-to-vesicles morphological transition in micelles from block copolymer/surfactant complexes

Metastable spherical micelles have been obtained by mixing in chloroform poly(styrene)-block-poly(4-vinylpyridine) diblock copolymers with perfluorinated surfactants bearing a carboxylic acid head. Dilution of these initial micelles triggers a morphological reorganization resulting in the formation of more stable vesicles. This transition can be advantageously used to encapsulate molecules of interest.     

The Formulation of Four-Components Practically Perfluorinated Microemulsions

Microheterogeneous systems consisting of sodium perfluorooctanoate ( 1 ), 2, 2, 3, 3, 4, 4, 4-heptafluoro-1-butanol ( 2 ), perfluorohexane ( 3 ) and water, representing the first practically perfluorinated microemulsions based on ionic surfactants have been formulated. A pseudoternary phase diagram shows a central region of turbid or transparent gels and two regions of monophasic systems (O/W- and W/O-microemulsions) which have been characterized by NMR. spectroscopy.     

Conformation of amphiphilic branch chain in copolymer surfactants on interface

The conformation of amphiphilic branch chain in a new type of copolymer surfactants on interface was studied. The results of laser light scattering demonstrated that the branch chain can only lie on the air/water interface. By means of XPS measurement with variable angles, the molecular conformations in different thickness of the copolymer layer were obtained. Depending on the chemical nature of the copolymer surfactants, the oxyethylene segments of the branch chains will have loop-train, train, or loop molecule conformations on the surface. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 827–830, 1997     

Biocompatible surfactants for water-in-fluorocarbon emulsions

Drops of water-in-fluorocarbon emulsions have great potential for compartmentalizing both in vitro and in vivo biological systems; however, surfactants to stabilize such emulsions are scarce. Here we present a novel class of fluorosurfactants that we synthesize by coupling oligomeric perfluorinated polyethers (PFPE) with polyethyleneglycol (PEG). We demonstrate that these block copolymer surfactants stabilize water-in-fluorocarbon oil emulsions during all necessary steps of a drop-based experiment including drop formation, incubation, and reinjection into a second microfluidic device. Furthermore, we show that aqueous drops stabilized with these surfactants can be used for in vitro translation (IVT), as well as encapsulation and incubation of single cells. The compatability of this emulsion system with both biological systems and polydimethylsiloxane (PDMS) microfluidic devices makes these surfactants ideal for a broad range of high-throughput, drop-based applications.     

Effect of alkyl chain asymmetry on catanionic mixtures of hydrogenated and fluorinated surfactants

In this work we studied and compared the physicochemical properties of the catanionic mixtures cetyltrimethyl-ammonium bromide–sodium dodecanoate, cetyltrimethyl-ammonium bromide–sodium perfluorodacanoate, octyltrimethylammonium bromide–sodium perfluorodacanoate and cetyltrimethyl-ammonium bromide–sodium octanoate by a combination of rheological, transmission electron microscopy (TEM) and polarized optical microscopy measurements. The binary mixtures of the surfactants have been analyzed at different mixed ratios and total concentration of the mixture. Mixtures containing a perfluorinated surfactant are able to form lamellar liquid crystals and stable spontaneous vesicles. Meanwhile, system containing just hydrogenated surfactants form hexagonal phases or they are arranged in elongated aggregates.     

The radiation degradation of polytetrafluoroethylene resulting in low-molecular and functionalized perfluorinated compounds

The degradation of polytetrafluoroethylene (PTFE) by high energy radiation with a high dose and in presence of oxygen forms perfluorinated carboxylic acids, among other compounds. In an inert atmosphere (in nitrogen) mixtures of perfluorinated olefines and paraffins of different chain length ranges are obtained. This process represents a new alternative of the synthesis of special active components, such as fluorocarbon surfactants, fluorine containing textile finishing agents, special dielectrics and others. Irradiation of the resulting perfluorinated paraffins (in nitrogen) and of gaseous degradation products of PTFE leads to a significant increase in the yield of perfluorinated olefines. Reaction mechanisms are discussed. Recombinations of radicals obtained by irradiation form branched molecules. The reactions are diffusion controlled. Irradiation of high molecular PTFE leads to low branching. The degree of branching of molecules increases in correlation with a decrease of viscosity of the reaction medium. An apparatus conception pertaining to the process of a continuous degradation of PTFE to perfluoroolefines and perfluoroparaffins in the favourable chain length ranges from six to 14 carbon atoms, according to application, is described. An essential component of this conception is the use of a target which consists of a tempered thin layer which is moved into an inertly processed reactor for irradiation. The action of high energy radiation of relatively low dose in air in presence of reactive substances leads to a finely grained PTFE powder with functional groups, which can be mixed easily with liquids, solutions and polymers.     

Batch and column study: sorption of perfluorinated surfactants from water and cosolvent systems by Amberlite XAD resins

Amberlite XAD resins have been employed to a great extent as the sorbent for removing or concentrating organic compounds from different matrices. We present for the first time a systematic study on the sorption of perfluorochemical (PFC) surfactants, an emerging class of environmental contaminants, by XAD-7HP (moderately polar) and XAD-2 (nonpolar). The results show that XAD-7HP can strongly sorb PFCs at circumneutral pH; the isotherm-determined linear sorption coefficient can reach 10(6)L/kg. On the other hand, the sorption coefficient for XAD-2 was two orders of magnitude lower than that for XAD-7HP. PFC sorption on XAD-7HP increased with an increase of the perfluorocarbon chain length of PFC and a decrease of the solution pH, indicating the importance of hydrophobic and electrostatic effects. The sorption coefficient for XAD-7HP reduced markedly with increasing fraction of the organic cosolvent (methanol) in the water-cosolvent mixture; however, the trend could not be predicted by a log-linear cosolvency model. Furthermore, the statistical analysis of column test results showed that after regeneration XAD-7HP can be used at least eight times without significant loss of performance. Finally, the experimental results imply that XAD-7HP sorption of shorter-chained PFCs (≤5 perfluorinated carbons) from water can be thermodynamically favorable.     

以全氟丁基为基础的具有高表面活性的氟表面活性剂

氟表面活性剂的环境和生物降解问题是最近的热点, 特别是全氟长链(≥C8)氟表面活性剂的应用限制乃至禁用已成为必然趋势. 本文合成了一种以短链的全氟丁基为基础的阳离子氟表面活性剂, N-[3-(二甲基胺基)丙基]全氟丁基磺酰胺盐酸盐(C4F9SO2NH(CH2)3NH(CH3)+2Cl-, 简称为PFB-MC). 该表面活性剂适用于强酸性环境, 具有极高的表面活性, 其溶液最低表面张力(19.80 mN·m-1)和通常的氟表面活性剂相当. 通过表面张力方法得到了固定pH(pH=2.6-2.7)情况下PFB-MC的表面张力-浓度对数(γ-lgc)曲线, 以及该pH下外加盐([NaCl]=0.1 mol·L-1)对表面张力的影响; 并进一步研究了pH对PFB-MC在其临界胶束浓度(cmc)前后的表面张力的影响.     

A comparative study of the physicochemical properties of perfluorinated and hydrogenated amphiphiles

In this work we studied and compared the physicochemical properties of perfluorinated (sodium perfluoroheptanoate, C7FONa, and perfluorooctanoate, C8FONa) and hydrogenated (sodium octanoate, C8HONa, decanoate, C10HONa, and dodecanoate, C12HONa) amphiphiles. First, we determined their Krafft points to study the solubility and appropriate temperature range of micellization of these compounds. The critical micelle concentration (cmc) and ionization degree of micellization (beta) as a function of temperature (T) were estimated from conductivity data. Plots of cmc vs T appear to follow the typical U-shaped curve with a minimum T(min). The results show that the surfactants with CF2/CH2 ratio of 1.5 between alkyl chains (C12HONa-C8FONa and C10HONa-C7FONa) have nearly the same minimum value for cmc against temperature. The comparison between the cmc of hydrogenated amphiphiles and the corresponding perfluorinated amphiphiles must be done at this point. Thermodynamic functions of micellization were obtained by applying different theoretical models and choosing the one that best fit our experimental data. Although perfluorinated and hydrogenated amphiphiles present similar thermodynamic behavior, we have found a variation of 1.3 to 1.7 in the CF2/CH2 ratio, which did not remain constant with temperature. In the second part of this study the apparent molar volumes and adiabatic compressibilities were determined from density and ultrasound velocity measurements. Apparent molar volumes at infinite dilution presented the ratio 1.5 between alkyl chains again. However, apparent molar volumes upon micellization for sodium perfluoroheptanoate indicated a different aggregation pattern.     

Microcalorimetric study on micellization of nonionic surfactants with a benzene ring or adamantane in their hydrophobic chains

The micellization of a novel family of nonionic surfactants poly(oxyethylene) glycol alkyl ethers has been studied by microcalorimetry. One of the surfactants has adamantane, and the other nonionic surfactants have a benzene ring in their hydrophobic chains, which moves from the terminal of the hydrophobic chain toward the headgroup. Moreover, the alkyl chain of the nonionic surfactants is straight or branched. Both the critical micelle concentration (cmc) and the thermodynamic parameters associated with the micelle formation have been obtained. The cmc decreases and the enthalpy of micelle formation (deltaH(mic)) becomes less positive gradually as the length of hydrophobic chain increases, whereas the values of cmc and deltaH(mic) tend to increase for the surfactants with a longer ethylene oxide chain. However, the deltaH(mic) value of the surfactant with seven carbon atoms in a hydrophobic chain is more positive than that of the surfactant with six carbon atoms in a hydrophobic chain. Comparing with the nonionic surfactant with a methylene hydrophobic chain, the surfactants with benzene rings and adamantane groups have larger cmc values and the cmc values increase with the size of the groups. Furthermore, moving the phenyl group from the terminal of the hydrophobic chain to the neighbor of the hydrophilic headgroup leads to the decreased cmc. Both the variation of hydrophobic interaction from the movement of phenyl group and pi-pi interaction among adjacent phenyl groups affect deltaH(mic) values.     

Influence of the surfactant chain length on the fluorescence properties of a water-soluble conjugated polymer

In this work, we report the influence of surfactant chain length and surfactant concentration on the photoluminescence (PL) of water-soluble pi-conjugated poly(thienyl ethylene oxide butyl sulfonate) (PTE-BS). We have used alkylammomium surfactants with 8, 9, 10, and 12 carbon atoms per hydrocarbon chain. The surfactant concentration was varied from 0.125 the critical micelle concentration (CMC) up to 2 times the CMC. The results show that at premicellar concentrations all the surfactants promote the polymer aggregation inducing an increase in the interchain charge transfer by pi-pi interactions, which competes with PL emission processes. However, in the premicellar range, the polymer PL emission is sharply affected by the surfactant chain length. Thus, the PL is quenched by the surfactants with the shortest tails, whereas the surfactants with the longest ones provoke an enhancement of the PL emission. This behavior has been associated with the capacity of the surfactants with the longest hydrocarbon chains to accommodate their tails inside the polymer, obstructing the appearance of pi-pi interchain interactions during aggregation and reducing intrachain defects. By contrast, at the CMC, the surfactant chain length does not modify the PL emission, since the excess of surfactant inhibits polymer aggregation, thus enhancing the efficiency of light emissive processes.     

Preconcentration and decomposition of perfluorinated carboxylic acids on an activated charcoal cartridge with sodium biphenyl reagent and its determination at microg L(-1) level on the basis of flow injection-fluorimetric detection of fluoride ion

Perfluorinated surfactants of heptafluorobutylate and pentadecafluorooctanoate ions were adsorbed on an activated charcoal cartridge and decomposed with sodium biphenyl (SBP) reagent to form inorganic fluoride ion. The fluoride ion thus formed was determined by flow injection analysis (FIA) using quercetin-Zr complex as a fluorimetric reagent, where λ_ex and λ_em were 422 and 491 nm, respectively. The limit of detection for fluoride ion by the FIA system was developed to 1.1 × 10⁻⁶ M (signal to noise ratio of three), when 50% (v/v) tetrahydrofuran (THF) was used as a dissolving solvent for quercetin. The perfluorinated surfactants in the sample solution were quantitatively adsorbed on the cartridge containing 100 mg of activated charcoal and were decomposed with 0.5 mL of sodium biphenyl reagent after drying thoroughly by flowing through dry nitrogen gas. The fluoride ion formed was recovered with 3 mL of purified water as an eluent, and it was determined by the fluorimetric flow injection system. The blank fluorescence signal accompanied during the adsorption/decomposition on the cartridge was reduced by washing the activated charcoal with acetone. The blank signal was also observed from dimethoxyethane, which was used in sodium biphenyl reagent. When 600 mL sample solution was used and 200 times enrichment was applied, the heptafluorobutylate and pentadecafluorooctanoate ions at the concentrations of 2.1 μg L⁻¹ were quantitatively recovered as fluoride ion, and the limit of detections for the perfluorinated surfactants were 0.3 and 0.3 μg L⁻¹ for the two perfluorinated surfactants, respectively (3 sigma of the blank signal).     

Synthesis and Characterization of Self-Assembling Some Thiol Surfactants on Gold Nanoparticles

The purpose of this work is to study the self-assembling of some synthesized thiol surfactants namely (mercaptopropane-, mercaptohexane-, mercaptooctane-, and mercaptodecane sodium sulfonate) on the fabricated gold nanoparticles. The self-assembling of these surfactants on gold nanoparticles characterized using different techniques such as FTIR spectroscopy, UV spectroscopy, and transmission electron microscopy (TEM). Spectroscopic evidence suggests that the synthesized thiol surfactants have been attached to the gold nanoparticles. The effect of self-assembling of these surfactants on the size of the gold nanoparticles was studied using TEM images. The growth of the gold nanoparticles was investigated with respect to the increase of alkyl chain in the synthesized thiol surfactants. The results show that the stabilization of gold nanoparticles was affected by the increase in alkyl chain length of these surfactants. The effect of gold nanoparticles on the interfacial tension and the emulsion stability of these surfactants with crude oil was studied.