Adsorption Of Cationic Surfactants Research Articles

Adsorption of Cationic Surfactants onto Photoresist Surfaces-A Way to Reduce Pattern Collapse in High Aspect Ratio Patterning

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Adsorption of Some Alkyloxyethylene Pyridinium Chlorides at Solid-Water Interface

The adsorption of cetylalkyl pyridinium and alkyloxyethylene pyridinium chlorides at the silica-alumina water interface at ph =7 and 25 0C was analyzed to determine the type of interaction between surfactant molecules and solid substrat between adsorbed adiacent molecules and with the surfactant molecules in the equilibrium water solution. The experimental adsorption isotherm for the entire concentration range consists of four regions with the maximum adsorption attained at the critical micelle concentration of each surfactant in aqueous solutions. Different models and equations of adsorption suitable to describe different types of forces implicated in adsorption of cationic surfactant at the opposite charged solid surfaces were applied. The free energy of adsorption, free energy of hydrophobic interaction and mean surface aggregation number were calculated. Insertion of oxyethylene groups leads to the increase of the hydrophobicity of these cationic surfactants. From the calculated free energy of adsorption through electrostatic and van der Waals interactions different surface structures were attributed to each region: neutralization of electrical charges, formation of hemimicelles, admicelles and bilayers.

Adsorption of Cationic Monomeric and Gemini Surfactants on Montmorillonite and Adsolubilization of Vitamin E

Adsorption of a cationic gemini surfactant (1,2-bis(dodecyldimethylammonio) ethane dibromide, 12-2-12) and the corresponding monomeric surfactant (dodecyltrimethylammonium bromide, DTAB) on montmorillonite has been characterized with a combination of adsorption isotherm, interlayer spacing and FT-IR spectroscopic data. Adsolubilization of vitamin E into the adsorbed surfactant layers has also been studied. The adsorption isotherm data reveal that the adsorption of the two surfactants is driven by the two factors: one is the cation exchange that occurs on the interlayer basal planes and the other is the hydrophobic interaction between hydrocarbon chains of the surfactants. Although the adsorbed amount measured in the saturation region (in mol g(-1)) is almost identical for the two surfactants, the conformation of the intercalated surfactant molecules differs significantly from each other. The adsorption of DTAB results in a lateral bilayer arrangement in the limited interlayer space, whereas 12-2-12 gives a normal bilayer arrangement in the expanded interlayer space. Adsolubilization of vitamin E takes place into the adsorbed surfactant layers, and interestingly, all the vitamin E molecules added in the montmorillonite suspensions are hybridized at lower surfactant concentrations due to the great specific surface area of the clay material. Since the maximum adsolubilization amount is usually obtained just below the critical micelle concentration, the gemini surfactant is deemed to be more efficient than the corresponding monomeric one to achieve the great adsolubilization amount.

Adsorption of Anionic–Cationic Surfactant Mixtures on Metal oxide Surfaces

AbstractThis research evaluates the adsorption of anionic and cationic surfactant mixtures on charged metal oxide surfaces (i.e., alumina and silica). For an anionic‐rich surfactant mixture below the CMC, the adsorption of anionic surfactant was found to substantially increase with the addition of low mole fractions of cationic surfactant. Two anionic surfactants (sodium dodecyl sulfate and sodium dihexyl sulfosuccinate) and two cationic surfactants (dodecyl pyridinium chloride and benzethonium chloride) were studied to evaluate the effect of surfactant tail branching. While cationic surfactants were observed to co‐adsorb with anionic surfactants onto positively charged surfaces, the plateau level of anionic surfactant adsorption (i.e., at or above the CMC) did not change significantly for anionic–cationic surfactant mixtures. At the same time, the adsorption of anionic surfactants onto alumina was dramatically reduced when present in cationic‐rich micelles and the adsorption of cationic surfactants on silica was substantially reduced in the presence of anionic‐rich micelles. This demonstrates that mixed micelle formation can effectively reduce the activity of the highly adsorbing surfactant and thus inhibit the adsorption of the surfactant, especially when the highly adsorbing surfactant is present at a low mole fraction in the mixed surfactant system. Thus surfactant adsorption can be either enhanced or inhibited using mixed anionic–cationic surfactant systems by varying the concentration and composition.

Amphiphile Adsorption on Rigid Polyelectrolytes

A theory is presented which quantitatively accounts for the cooperative adsorption of cationic surfactants to anionic polyelectrolytes. For high salt concentration we find that the critical adsorption concentration (CAC) is a bilinear function of the polyion monomer and salt concentrations, with the coefficients dependent only on the type of surfactant used. The results presented in the paper might be useful for designing more efficient gene delivery systems.

The adsorption of cationic surfactants on photoresist surfaces and its effect on the pattern collapse in high aspect ratio patterning

The collapse of photoresist patterns in high aspect ratio patterning is a defect that may reduce the production yield drastically. Recently, a novel method to reduce the pattern collapse was successfully applied: the rinse of the photoresist patterns with a cationic surfactant solution. In a previous study it was shown that one chosen surfactant adsorbs on both untreated photoresist surfaces and photoresist films that had undergone the whole photolithographic process. For this surfactant best pattern collapse reduction coincides with the formation of surfactant aggregates on the photoresist surface and with a maximum receding contact angle on processed photoresist. The present study investigates the influence of the hydrocarbon chain length of the surfactant on the pattern collapse reduction. The adsorption of surfactants of various chain length on unexposed and exposed photoresist was observed using null-ellipsometry and zeta potential measurements. Increasing the surfactant chain length shifts the adsorption domains to lower concentrations. It leads to an increased adsorbed amount and maximum contact angle as well as to a better pattern collapse reduction.

Dynamic adsorption of gemini and conventional cationic surfactants onto polyacrylonitrile

The role of dodecyltrimethylammonium bromide (DTAB) and a series of gemini cationic surfactants in the adsorption rate of methylene blue (MB) on acrylic fibres has been studied by means of TOC, UV–vis and FT-NMR spectroscopy. The influence of surfactant concentration, alkyl chain and spacer length of geminis has been investigated at different temperatures. The dye adsorption rate increases with increasing temperature, while the retarding action of gemini cationic surfactants is much stronger than that of the corresponding monomeric surfactants. There are small differences among the geminis with the same alkyl chain but with various spacer lengths.

Adsorption of conventional and gemini cationic surfactants in nonswelling and swelling layer silicate

The adsorption of conventional (cetyltrimethylammonium bromide) and its corresponding gemini cationic surfactant [ethanediyl-α,β-bis(cetyldimethylammonium bromide)] in both swelling (montmorillonite) and nonswelling (kaolinite) layer silicates was investigated by adsorption isotherms and X-ray diffraction techniques. Adsorption studies showed that the adsorption of gemini surfactant was more efficient than that of the corresponding conventional surfactant on both kaolinite and montmorillonite. The adsorption amount of both surfactants on montmorillonite was much higher than on kaolinite, which was related to the nature of the clays. Although the molar adsorption amount of both surfactants on the same clay were almost identical, there existed some differences in the microstructure of adsorption layer revealed by X-ray diffraction experiments.

Self-Aggregation of Cationic Surfactants onto Oxidized Cellulose Fibers and Coadsorption of Organic Compounds

In this work, the adsorption of cationic surfactant and organic solutes on oxidized cellulose fibers bearing different amounts of carboxylic moieties was investigated. The increase in the amount of -COOH groups on cellulose fibers by TEMPO oxidation induced a general rise in surfactant adsorption. For all tested conditions, that is, cellulose oxidation level and surfactant alkyl chain length (C12 and C16), adsorption isotherms displayed a typical three-region shape with inversion of the substrate zeta-potential which was interpreted as reflecting surfactant adsorption and aggregation (admicelles and hemimicelles) on cellulose fibers. The addition of organic solutes in surfactant/cellulose systems induced a decrease in surfactant cac on the cellulose surface thus favoring surfactant aggregation and the formation of mixed surfactant/solute assemblies. Adsorption isotherms of organic solutes on cellulose in surfactant/cellulose/solute systems showed that solute adsorption is strictly correlated to (i) the surfactant concentration, solute adsorption increases up to the surfactant cmc, where solute partitioning between the cellulose surface and free micelles causes a drop in adsorption, and to (ii) solute solubility and functional groups. The specific shape of solutes adsorption isotherms at a fixed surfactant concentration was interpreted using a Frumkin adsorption isotherm, thus suggesting that solute uptake on cellulose fibers is a coadsorption and not a partitioning process. Results presented in this study were compared with those obtained in a previous work investigating solute adsorption in anionic surfactant/cationized cellulose systems to better understand the role of surfactant/solute interactions in the coadsorption process.

Cationic surfactant adsorption in the presence of divalent ions

The effect of divalent sulphate SO 4 2− anions and monovalent hydrosulphate HSO 4 − anions, which are simultaneously present in solution due to dissociation equilibrium, on the surface tension of cethyltrimethyl ammonium salts C 16TABr (CTABr) and C 16TAHSO 4 (CTAHSO 4), was investigated. The surface tension was determined by the pendant drop-shape analysis method. The previously proposed “surface quasi two-dimensional electrolyte” (STDE) model of ionic surfactant adsorption, based on the assumption that the surfactant ions and counterions can undergo non-equivalent adsorption within the Stern at layer at air/solution interface, was extended for the description the adsorption of ionic surfactants in presence of multivalent electrolytes. The results indicate that a very good description of experimental data by the developed model can be achieved. They show that monovalent anions like Br −, Cl − or HSO 4 − ions decrease more effectively the surface tension of investigated surfactant than SO 4 2− ions if the solutions of the same ionic strength are compared. That can be explained in terms of low ability of divalent SO 4 2− ions to penetrate the surface layer due to their strong hydration. The ability to decrease the surface tension of cationic surfactants by SO 4 2− follow the place taken by this anion in the Hofmeister series.

Removal of solvent-based ink from printed surface of high-density polyethylene bottles by alkyltrimethylammonium bromides: Effects of pH, temperature, and salinity

The effects of pH, temperature, and salinity on the removal of solvent-based ink from high-density polyethylene (HDPE) surfaces were investigated using three alkyltrimethylammonium bromides (i.e., dodecyl-, tetradecyl-, and hexadecyl-trimethylammonium bromide or DTAB, TTAB, and CTAB, respectively). Ink removal increases with increasing concentration, increasing pH, decreasing temperature, and increasing salinity of the CnTAB solutions. The zeta potential of ink becomes more positively charged with increasing pH as well as concentration and alkyl chain length of CnTAB, indicating that adsorption of CnTAB on ink pigment occurred more readily with an increase in any of those parameters. The solubilization of epoxy ink binder was found to increase with increasing surfactant concentration, decreasing temperature, and increasing salinity of the CnTAB solutions. Adsorption of cationic surfactant onto the ink pigment particles and solubilization of ink binder molecules into surfactant micelles are important mechanisms causing ink removal from the plastic surface.

Adsorption of dodecyl trimethylammonium and hexadecyl trimethylammonium onto kaolinite — Competitive adsorption and chain length effect

Adsorption of dodecyl trimethylammonium (DDTMA) and hexadecyl trimethylammonium (HDTMA) from single and mixed surfactant solutions onto kaolinite was investigated in this study. It was found that the surfactant chain length had minimal effects on the amount of cations desorbed. In contrast, the amounts of surfactant and counterion bromide adsorbed were strongly affected by surfactant chain lengths. Compared to DDTMA, HDTMA and counterion bromide adsorption was much higher. This fact further verified that both cation exchange and hydrophobic interaction played an important role in cationic surfactant adsorption on negatively charge mineral surfaces. The results also indicate that chain length has a minimal influence on surfactant adsorption via cation exchange, but a longer chain length promotes stronger hydrophobic interaction and thus, resulted in a higher surfactant adsorption.

The effect of adsorbed carboxymethyl cellulose on the cotton fibre adsorption capacity for surfactant

The research reported in this paper demonstrates that the capacity of cotton fibres to adsorb cationic surfactants as well as the rate of the adsorption process can be increased by adsorbing carboxymethyl cellulose (CMC) onto the fibre surfaces; in addition, the adsorption can be restricted to the fibre surface. CMC was deposited by means of adsorption from an aqueous solution. The adsorption of N-cetylpyridinium chloride (CPC) from an aqueous solution onto the CMC-modified fibres was measured using UV-spectrometric determination of the surfactant concentration in the solution. Adsorption onto the cotton fibres was studied in a weakly basic environment (pH 8.5) where cotton fibres are negatively charged and the CPC ion is positively charged. Modification of the fibres by adsorption of CMC introduces new carboxyl groups onto the fibre surfaces, thereby increasing the adsorption capacity of the fibres for CPC. The initial rate of adsorption of CPC increased proportionally with the amount of charge; however, this rate slowed down at high degrees of coverage on fibres with a high charge. The adsorption of cationic surfactant to the anionic surface groups was stoichiometric, with no indication of multilayer or admicelle formation. It was evident that the acidic group content of the fibres was the primary factor determining cationic surfactant adsorption to these fibres.

Effect of cationic surfactant adsorption on the rheological and surface properties of bentonite dispersions

In this study, the adsorption, bridging, and intercalation effects of a cationic surfactant, benzyldimethyltetradecyl ammonium chloride (BDTDACl), on bentonite clay suspensions was investigated. The adsorption, rheological behaviors, and colloidal properties of the clay dispersions were determined as a function surfactant concentration. Adsorption isotherms were obtained using the batch-equilibrium technique. The rheological behavior of the clay suspensions was obtained by shear stress-shear rate measurements within 0–350 s−1 shear rates. The structure of the composite particles was analyzed by using X-ray diffraction analysis and it was found that the expansions of basal d-spacings are less than 16.80 Å, suggesting a monolayer structure.

Inhibition efficiencies of some organic compounds on the corrosion of zinc in alkaline media

PurposeThe purpose of this paper is to investigate the inhibiting properties of six quaternary ammonium salts, three cationic surfactants and two non‐ionic surfactants in 2 M KOH. An attempt also was made to correlate some molecular parameters of these compounds with their corrosion inhibitor efficiency.Design/methodology/approachThe inhibition efficiencies of quaternary ammonium salts, cationic surfactants and non‐ionic surfactants on the corrosion of zinc in 2 M KOH solution were investigated by potentiodynamic polarisation, electrochemical impedance spectroscopy and linear polarisation methods.FindingsInhibition efficiencies of quaternary ammonium salts were found to be due to physical absorption on the cathodic sides of zinc electrode and dependence of inhibition efficiencies on substituents were found. Physical adsorption of cationic surfactants on zinc electrode slowed down both anodic and cathodic reactions; thus they were found to be mixed type inhibitors. On the other hand, inhibition behaviour of non‐ionic surfactants was found to be due to adsorption on zinc via polar groups. It was found that non‐ionic surfactants behaved as mixed type inhibitors.Originality/valueClarifies the role of molecular structure and substituents on the inhibition efficiency of surfactants and quaternary ammonium compounds on the corrosion of zinc in alkaline media.

Dynamics of Adsorption of Cationic Surfactants at Air—Water and Solid—Liquid Interfaces

AbstractFor Abstract see ChemInform Abstract in Full Text.

Monolayer behavior of silica particles at air/water interface: A comparison between chemical and physical modifications of surface

Silica particles are hydrophobized either by chemical graft of alkyl chains or by physical adsorption of cationic surfactants, alkyltrimethylammonium bromide. The effects of the two modification methods on the monolayer behavior of silica particles at the air/water interface are studied, as well as the packing structure of the particulate films. The results show that the hydrophobicity of particles chemically modified by octanol (SiO 2-C 8) and dodecanol (SiO 2-C 12) are similar and higher than that modified by butanol (SiO 2-C 4). The monolayer composed of particles with higher hydrophobicity shows a large lift-off area, higher compressibility, and significant hysteresis due to the higher particle–particle interaction. As a result, the particulate films exhibit 2-dimensional (2D) aggregative domains of closely-packed structure, but with particle free regions presenting among the domains. The monolayer prepared by SiO 2-C 4 shows a contrary behavior resulted from the higher particle–water interaction. The particles modified by adsorption of cationic surfactants have an amphiphilic property at the air/water interface. Such monolayer exhibits lower compressibility and hysteresis, higher re-spreading characteristic, and a lower collapse pressure compared with those of the chemically modified particles. A particulate film with high uniformity and closely-packed structure can be obtained by using the octyltrimethylammonium bromide (OTAB) modified particles. When the alkyl chain of surfactant increases, the packing of the particles becomes looser. Such phenomenon is probably caused from the higher probability for the long-chain surfactants to stay at the air/water interface which obstructs the intimate contact of particles.

Adsorption of a Cationic Surfactant onto Cellulosic Fibers I. Surface Charge Effects

The adsorption of four cationic surfactants with different alkyl chain lengths on cellulose substrates was investigated. Cellulose fibers were used as model substrates, and primary alcohol groups of cellulose glycosyl units were oxidized into carboxylic groups to obtain substrates with different surface charges. The amount of surfactant adsorbed on the fiber surface, the fiber zeta-potential, and the amount of surfactant counterions (Cl(-)) released into solution were measured as a function of the surfactant bulk concentration, its molecular structure, the substrate surface charge, and the ionic strength. The contribution of each of these parameters to the shape of the adsorption isotherms was used to verify if surfactant adsorption and self-assembly models usually used to describe the behavior of surfactant/oxide systems can be applied, and with which limitations, to describe cationic surfactant adsorption onto oppositely charged cellulose substrates.

Micellar-enhanced electrodialysis: Influence of surfactants on the transport properties of ion-exchange membranes

Thin layers of ionic surfactants were formed on the surfaces of ion-exchange membranes by adsorption with electrostatic interactions and were conformed by FTIR spectra. The effect of the adsorption on the transmission characteristics were investigated by membrane resistance and permselectivity studies, and it was found that adsorption of cationic surfactant onto the cation-exchange membrane and anionic surfactant onto the anion-exchange membrane associated with the increase in membrane resistance while decrease in membrane permselectivity, which became limiting beyond the critical micelle concentration of respective surfactant. Based on the studies schematic model for the orientations of surfactant molecules on the membranes surfaces under the electrodialytic conditions was presented. Improvement in the electrodialysis (ED) process efficiencies was observed due to the adsorption of the ion-exchange membranes surfaces because of the reduction in the concentration gradient between dilute and concentrated compartments of the ED unit, and thus back diffusion. This phenomenon is also schematically presented by the concentration profiles across the ion-exchange membranes under the electrical gradient in the polarized conditions. Based on the experimental results so called micellar-enhanced electrodialysis has been proposed for the efficient electrolyte separation up to very low concentration (with high purity) with reduced energy consumption, concentration polarization and improved limiting current density.

Origin of the long-range attraction between surfactant-coated surfaces

We compare the "long-range hydrophobic forces" measured (i) in the "symmetric" system between two mica surfaces that had been rendered hydrophobic by the adsorption of a double-chained cationic surfactant, and (ii) between one such hydrophobic surface and a hydrophilic surface of bare mica ("asymmetric" case). In both cases, the forces were purely attractive, stronger than van der Waals, and of long-range, as previously reported, with those of the asymmetric, hydrophobic-hydrophilic system being even stronger and of longer range. Atomic force microscopy images of these surfaces show that the monolayers transform into patchy bilayers when the surfaces are immersed in water, and that the resulting surfaces contain large micrometer-sized regions of positive charges (bilayer) and negative charges (bare mica) while remaining overall neutral. The natural alignment of oppositely charged domains as two such surfaces approach would result in a long-range electrostatic attraction in water, but the short-range, "truly hydrophobic" interaction is not explained by these results.