Effect of Organic Counterions on the Properties of N-Lauryl Diisopropanolamine Surfactants

The influence of counterions on the surface properties of N-lauryl diisopropanolamine surfactants is delineated using conductometry and surface tension measurements. Twelve types of organic counterions have been studied: C₁–C₁₂ monocarboxylic acids anions. The surface properties of the synthesized surfactants, including surface tension, critical micelle concentration (CMC), effectiveness (π_CMC), efficiency (pC₂₀), maximum surface excess (Γ_max), minimum surface area (A_min), Gibbs energy of micellization (ΔG_mic), and adsorption (ΔG_ad) processes in the aqueous. The biodegradability of the prepared surfactants was tested in river water using the die-away method. Petroleum-collecting and petroleum-dispersing capacities of the synthesized compounds on the surface of water of varying mineralization degree have been studied.     

Theory of diffusion-controlled adsorption kinetics at the expanding planar surface with a constant area rate

The diffusion equation for the expanding surface was solved and a corresponding general expression of dynamic surface adsorption was derived. For the short-time adsorption, a special factor 1/3, which reflected the effect of the expanding surface on the adsorption, appeared in the equation. In addition, the effects of the surface expansion on subsurface concentration (ϕ(t)), dynamic surface adsorption (Γ(t)), dynamic surface tension (γ(t)) and the adsorption mechanism were discussed. In contrast to the adsorption on a still planar surface, ϕ(t) and Γ(t) are smaller, but γ(t) increased. The adsorption mechanism will be the same as long as the corresponding theories are used.     

Electrophoresis of large colloidal particles with surface charge layers. Position of the slipping plane and surface layer thickness

A theory is proposed for the electrophoresis of a large colloidal particle with a surface charge layer. The slipping plane is assumed to be located within the surface layer but may not be located at the boundary between the surface layer and the particle core. In previous studies, the depth of the slipping plane is assumed to coincide with the surface layer thickness. The present theory makes it possible to examine the separate dependence of the electrophoretic mobility on the position of the slipping plane and on the surface layer thickness. It is shown that, at constant amount of particle-fixed charges in the surface layer, the mobility increases as the depth of the slipping plane (d _s ) increases, while it decreases as the surface layer thickness (d _c ) increases, causing a mobility maximum in some cases ifd _s =d _c . Several approximate analytic expressions for the mobility are presented.     

Surface-grafting onto aramid powder: reaction of acyl chloride groups on the surface with functional polymers having terminal hydroxyl or amino groups

The surface-grafting of polymers onto aramid, poly(p-phenylene terephthalamide), powder surface by the reaction of acyl chloride groups on the surface with functional polymers having terminal hydroxyl and amino groups was investigated. The introduction of acyl chloride groups onto the aramid powder surface was achieved by the reaction of the aramid powder with adipoyl dichloride: the acyl chloride group content of the surface was estimated to be 1.14 mmol/g (0.17 mmol/m²) by elemental analysis. It was found that by the reaction of acyl chloride groups on the surface with functional polymers, such as terminal diol-type poly(propylene oxide) (PPG) and terminal diamine-type poly(dimethylsiloxane) (SDA), these polymers were grafted onto the aramid powder surface; the percentage of surface grafting of PPG and SDA onto the aramid powder was 16.7 and 22.4%, respectively. The thermogravimetric curve of PPG surface-grafted aramid powder exhibited an initial weight loss at about 250°C and a second weight loss at about 500°C. This indicated that the grafting of PPG is limited to the powder surface. The wettability of the aramid powder surface turned from hydrophobic to hydrophilic by the surface-grafting of PPG onto the surface.     

Use of electrochemical impedance spectroscopy to characterise the physical properties of ex situ reconstructed sea surface microlayer

The objective of this work was to develop electrochemical impedance spectroscopy (EIS) to characterise the physical properties of the sea surface microlayer ( ssm ). Samples from Lake Rogoznica in Croatia were extracted by n-hexane and dichloromethane (dcm) respectively and transferred to mercury electrodes. The EIS results were compared with those of a model phospholipid, dioleoyl phosphatidylcholine (DOPC) which forms near defect-free monolayers on a mercury surface. The ssm extracts formed inhomogeneous monolayers on the mercury surface and the dcm ssm extract monolayer showed greater surface roughness than the hexane ssm extract. The hexane ssm extract introduced defects and a greater surface roughness into mixed DOPC- ssm extract monolayers than the dcm ssm extract due to the lower compatibility of the non-polar hexane extract with the DOPC than that of the polar ssm extract. In addition, the dcm ssm component in the mixed DOPC- ssm monolayer showed an association with pyrene added to the solution.     

Aggregation behavior and adsorption properties of salt-free catanionic surfactant mixtures containing tetradecyltrimethyl ammonium salts

The aggregation behavior of salt-free catanionic surfactants, tetradecyltrimethyl ammonium hydroxide (TTAOH)/fatty acid (FA) including octanoic acid (OA), decylic acid (DA) and lauric acid (LA) in aqueous solutions were studied. The critical micelle concentration(cmc), surface tension at cmc (γ_cmc), surface excess (Г_max), mean molecular surface area (A_min), adsorption efficiency (pc₂₀) and surface tension reduction effectiveness (π_cmc) were obtained from surface tension isotherms. The influence of temperature on the surface tension of salt-free TTAOH/FA (TTAOF) systems was investigated. Data of adsorption dynamics indicated that at fixed adsorption time, the order of adsorption capacity was TTAOH?相似文献   

Relation between surface preconditioning and metal deposition in direct galvanic metallization of insulating surfaces

The relation between surface preconditioning and metal deposition in the direct galvanic metallization of different insulating polymer surfaces by the so-called PLATO technique was studied using electrochemical and surface analytical methods. AFM, XPS and contact angle measurements show that the chromic acid etching of original polymer surfaces leads to an increase of the surface energy and hydrophilicity of polymer substrates due to both surface roughening and the formation of -COOH and/or -COH surface groups. However, decisive for the subsequent surface activation with cobalt sulfide is the increase in surface roughness. The influence of the degree of activation and the electrode potential on the kinetics of Ni metallization was studied by current transient measurements on activated line-shaped structures. The results suggest that the electrochemical reduction of cobalt sulfide to cobalt is a necessary step to induce the process of Ni electrodeposition. Successful Ni metallization could be obtained on ABS (acrylonitrile-butadiene-styrene) and PEEK (poly-ether-ether-ketone) surfaces. The lateral propagation rate, V _x , of the depositing Ni layer depends exponentially on the applied potential and was found to be several orders of magnitude higher than the Ni deposition rate, V _z , in the normal z-direction (V _x /V _z =10²–10⁴). It was demonstrated that the approach involving cobalt sulfide pre-activation can also be applied successfully for metallization of oxidized porous silicon surfaces.Presented at the 3rd International Symposium on Electrochemical Processing of Tailored Materials held at the 53rd Annual Meeting of the International Society of Electrochemistry, 15–20 September 2002, Düsseldorf, Germany     

Studies on the Effects of Additional Components on Micellization of CTAB via Surface Tension Measurements

The effects of Tris-HCl buffer solution on the cmc of cetyltrimethylammonium bromide (CTAB) were studied by surface tension measurement. The result shows that the effect of the buffer solution depends on the interaction between CTAB and NaCl and the structure accelerants of water, Tris. A series of parameters, including the critical micelle concentration (cmc), the surface tension at cmc (γ_cmc), the adsorption efficiency (pC₂₀), and the effectiveness of surface tension reduction (∏_cmc) were obtained from the surface tension measurements in the presence of glycine with different concentration in the Tris-HCl buffer solution at 27°C. In addition, maximum surface excess concentration (Γ _max) and minimum surface area per molecule (A_min) at the air-water interface were estimated according to the Gibbs adsorption isotherm. The thermodynamic parameters (Δ C _p,m , Δ H _m,tr , Δ C _p,m,tr ) of micellization for CTAB in the absence and presence of glycine at different temperature were also been obtained.     

Surface Structure and Stereocomplex Formation of Enantiomeric Polylactide Blends Using Poly(dimethyl siloxane) as a Probe Polymer

In the stereocomplex between enantiomeric poly(l-lactide) (l-PLA) and poly(d-lactide), crystallites formed as a result of stereocomplexation, equimolar l- and d-lactide unit sequences are packed side by side. The stereocomplex exhibits a melting temperature higher by about 50 °C than that of each homopolymer. In this study, we attempt to obtain further insight into the stereocomplex-induced surface structure of enantiomeric PLA blend films. The design of the blend systems is based on principles of surface segregation of multicomponent polymeric systems with a low surface energy, triblock copolymer (l-PLA-b-PDMS-b-l-PLA) of l-PLA and poly-(dimethyl siloxane). (l-PLA-b-PDMS-b-l-PLA/l-PLA) blend films showed the surface segregation of PDMS, regardless of blend composition while the surface composition of PDMS in the (l-PLA-b-PDMS-b-l-PLA/d-PLA) blend films was strongly depended on blend composition or a degree of complexation. These results are likely due to strong interaction between d- and l-lactide unit sequences, which prevents the surface segregation of PDMS.     

ATRP of butyl acrylates from functionalized carbon black surfaces

The functionalization of carbon black surface with atom transfer radical polymerization (ATRP) initiating sites and subsequent ATRP of n‐butyl acrylate (n‐BA) and t‐butyl acrylate (t‐BA) from the surface of carbon black is reported. The polymerizations were carried out using CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as the primary catalytic system in anisole at 70 °C. The initiator density on carbon black surface was tuned and the effect of initiator density on the polymers grafted on the surface was illustrated. Polymerizations were also performed in the presence of a sacrificial initiator to indirectly monitor the molecular weight evolution of polymers formed in the system. Block copolymerization of t‐BA initiated from poly(n‐BA) grafted carbon black was conducted to achieve water‐dispersible carbon black composites after cleavage of the t‐butyl groups. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4695–4709, 2005     

Counterion-Dictated Self-Cleaning Behavior of Polycation Coating upon Water Action: Macroscopic Dissection of Hydration of Anions

The counterions of polydiallyldimethylammonium (PDADMA) coatings were altered by incubation in aqueous solutions of different electrolytes. Oil de-wetting on the resulting polycationic surfaces upon water action exhibited a straightforward connection with the Jones–Dole viscosity B-coefficient (Bη) sign of surface counteranions. Upon water action, surface counteranions with negative Bη render PDADMA coatings oil-adhering, but those with positive Bη furnish PDADMA coatings with excellent self-cleaning. The oil-adhering PDADMA surfaces can become self-cleaning upon water action in response to the Bη of surface counteranions sign-switching with increasing water temperature. Courtesy of surface counter-anions with Bη>0, self-cleaning PDADMA coatings enable not only conversion of conventional meshes into self-cleaning membranes for oil/water separation, but also regioselective maneuver of oil flow on polycationic surfaces according to the Bη sign of surface counteranions patterned atop.     

A Photonic Crystal Protein Hydrogel Sensor for Candida albicans

We report two‐dimensional (2D) photonic crystal (PC) sensing materials that selectively detect Candida albicans (C. albicans). These sensors utilize Concanavalin A (Con A) protein hydrogels with a 2D PC embedded on the Con A protein hydrogel surface, that multivalently and selectively bind to mannan on the C. albicans cell surface to form crosslinks. The resulting crosslinks shrink the Con A protein hydrogel, reduce the 2D PC particle spacing, and blue‐shift the light diffracted from the PC. The diffraction shifts can be visually monitored, measured with a spectrometer, or determined from the Debye diffraction ring diameter. Our unoptimized hydrogel sensor has a detection limit of around 32 CFU/mL for C. albicans. This sensor distinguishes between C. albicans and those microbes devoid of cell‐surface mannan such as the gram‐negative bacterium E. coli. This sensor provides a proof‐of‐concept for utilizing recognition between lectins and microbial cell surface carbohydrates to detect microorganisms in aqueous environments.     

Adsorption of uranyl species onto the rutile (110) surface: a periodic DFT study

To model the structures of dissolved uranium contaminants adsorbed on mineral surfaces and further understand their interaction with geological surfaces in nature, we have performed periodic density funtional theory (DFT) calculations on the sorption of uranyl species onto the TiO₂ rutile (110) surface. Two kinds of surfaces, an ideal dry surface and a partially hydrated surface, were considered in this study. The uranyl dication was simulated as penta‐ or hexa‐coordinated in the equatorial plane. Two bonds are contributed by surface bridging oxygen atoms and the remaining equatorial coordination is satisfied by H₂O, OH^?, and CO₃^2? ligands; this is known to be the most stable sorption structure. Experimental structural parameters of the surface–[UO₂(H₂O)₃]²⁺ system were well reproduced by our calculations. With respect to adsorbates, [UO₂(L1)_x(L2)_y(L3)_z]ⁿ (L1=H₂O, L2=OH^?, L3=CO₃^2?, x≤3, y≤3, z≤2, x+y+2z≤4), on the ideal surface, the variation of ligands from H₂O to OH^? and CO₃^2? lengthens the U? O_surf and U? Ti distances. As a result, the uranyl–surface interaction decreases, as is evident from the calculated sorption energies. Our calculations support the experimental observation that the sorptive capacity of TiO₂ decreases in the presence of carbonate ions. The stronger equatorial hydroxide and carbonate ligands around uranyl also result in U?O distances that are longer than those of aquouranyl species by 0.1–0.3 Å. Compared with the ideal surface, the hydrated surface introduces greater hydrogen bonding. This results in longer U?O bond lengths, shorter uranyl–surface separations in most cases, and stronger sorption interactions.     

The role of probe–probe interactions on the hybridization of double-stranded DNA targets onto DNA-modified magnetic microparticles

In this work, we have studied the effect of different probe lengths and surface densities on the hybridization of a 181-bp polymerase chain reaction product to probes tethered onto magnetic microparticles. Hybridization was shown to be favored by longer probes but only at probe surface densities where probe-to-probe interactions are absent. From these results, a simple rule was inferred for determining maximum surface densities above which hybridization signals decreased. According to this rule, if the average surface area occupied by an immobilized probe (Σ) is larger than the projected surface area of each tethered probe molecule (S _ss ), hybridization efficiency increases with surface density, whereas the reverse occurs when Σ −  S _ss  < 0.     

Molecular Weight Development of Surface and Solution Polymers in Surface‐Initiated Atom Transfer Radical Polymerization and Their Dependence on Radical Termination Modes

In the surface‐initiated atom transfer radical polymerization, the polymerization proceeds both in solution and on surface. This work reports a modeling study, describing the growth of the molecular weight and polydispersity of polymer both on surface and in solution. It is found that both surface radical termination and solution monomer consumption significantly suppress the growth rate of polymer layer. Besides, the former affects the molecular weights of polymer both on surface and in solution. If the termination rate constant in solution (k_t,sol–sol) is the same as that of surface and solution interfaces (k_t,sol–surf), and the surface termination (k_{t,surf–surf}) is negligible, then the polymers both on surface and in solution have the same molecular weight. However, if surface radicals terminate among themselves, the molecular weight of polymer on surface will lower than that in solution. Such termination is promoted by surface radical migration through activation/deactivation reactions in solution. When k_t,sol–surf <k_t,sol–sol, the molecular weight of surface polymer becomes higher than that in solution. This situation is resulted from surface radical trap due to a high grafting density.

     

Synthesis and Evaluation of Surface Activity of Gemini Borate Surfactants Based on Glucose Moiety

A series of Gemini borate surfactants were synthesized based on glucose molecule. Their chemical structures were confirmed using ¹H-NMR,¹³C nuclear magnetic resonance (NMR), and mass spectroscopy. The surface activities of these Gemini amphiphiles were measured, including surface tension (γ), critical micelle concentration (CMC), effectiveness (II_cmc), efficiency (pC₂₀), maximum surface excess (Γ_max), and minimum surface area (A_min) at different temperatures 25, 35, and 45°C either in pure water or in water–ethanol mixture (10%). Also, thermodynamic data including free energy, entropy, and enthalpy changes (ΔS, TΔS, ΔH) for adsorption at the air–water interface and also for micellization in surfactant solutions were calculated.     

A study of the surface analysis of some water‐soluble polymers by inverse gas chromatography

The surface characterization of 2‐(dimethylamino)ethylmethacrylate (DMA) and 2‐(N‐morpholino)ethylmethacrylate (MEMA) homopolymers and DMA–MEMA diblock copolymer was studied using inverse‐gas chromatography (IGC). The analyzed surface properties of (co)polymers were the dispersive component of the surface energy ( ) and the acid–base characters of (co)polymer surfaces. The specific free energy (ΔG^sp), enthalpy (ΔH^sp), and entropy (ΔS^sp) of adsorption of polar probes on (co)polymers were calculated. The values of ΔH^sp were correlated with both the donor and the modified acceptor numbers (AN) of the probes to quantify the acidic K_A and the basic K_D parameters of (co)polymer surfaces. The values obtained for the K_A and K_D parameters indicated basic characters for the surface of (co)polymers. The dispersive component values of the surface energy and the acid–base surface parameters of the DMA–MEMA diblock copolymer surface were found to be between those homopolymers as expected. Copyright © 2008 John Wiley & Sons, Ltd.     

Photoelectron spectroscopy and diffraction of surface nanoscale NbO/Nb(110) structures

X-ray photoelectron spectroscopy and diffraction (XPS and XPD) are applied to analyze oxygen-induced surface structures on the Nb(110) face formed due to oxygen segregation from the crystal bulk on thermal annealing to 2000 K in vacuum and/or oxygen adsorption in situ at temperatures above 1100 K. The Nb3d, O1s electronic states and valence band spectra of the NbO _x /Nb(110) surface are studied by XPS, and the results are compared with data for NbO, NbO₂, and Nb₂O₅ oxides. It is shown that niobium atoms entering the composition of surface oxide structures on Nb(110), from the standpoint of the nearest environment and chemical bond, are similar to metal states in NbO. The NbO _x layer thickness is estimated to be 0.5 nm. Two chemically inequivalent oxygen states are distinguished on Nb(110), which are, presumably, atomic chemisorbed oxygen on the parts of the clean surface of the Nb monolayer with hexagonal packing and oxygen in the composition of NbO _x -like linear clusters on Nb(110). A model of the NbO _x /Nb(110) surface takes into account a distortion of the structure of NbO _x clusters: a periodic vertical shift of metal atoms in Nb-chains and changes in Nb-O bond angles. Original Russian Text Copyright ? 2009 by M. V. Kuznetsov, A. S. Razinkin, and E. V. Shalaeva __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 50, No. 3, pp. 536–543, May–June, 2009.     

Surface Interactions of Radicals During Plasma Processing of Polymers

Surface interactions of radical species were investigated using the imaging of radicals interacting with surfaces (IRIS) technique during plasma surface modification of polymers. Three plasma systems were investigated by spatially probing the laser induced fluorescence of individual radical species and determining their surface scattering coefficients, S. The behavior of CF₂ moieties on polymer surfaces was studied using the fluorocarbon plasmas C₂F₆ and hexafluoropropylene oxide (HFPO). Three types of surface interactions were observed, surface generation of CF₂ (S > 1), surface loss of CF₂ (S < 1), and unit scattering (S = 1). Surface loss of CF₂ was seen in HFPO plasmas, while CF₂ was generated in C₂F₆ systems. The differences between these systems is believed to be the result of different overall surface interactions, specifically film deposition in the HFPO system and etching in the C₂F₆ system. Using NH₃ plasmas, the surface interactions of NH₂ radicals with polymers was also investigated. Here, NH₂ is generated at the surface of polyethylene and polytetrafluoroethylene substrates, but is consumed on polyimide substrates. Ion effects were also investigated by placing a grounded mesh in the path of the molecular beam to remove charged species.     

Physicochemical properties of {1-methyl piperazine (1) + water (2)} system at T = (298.15 to 343.15) K and atmospheric pressure

Densities (ρ) and viscosities (η) of aqueous 1-methylpiperazine (1-MPZ) solutions are reported at T = (298.15 to 343.15) K. Refractive indices (n_D) are reported at T = (293.15 to 333.15) K, and surface tensions (γ) are reported at T = (298.15 to 333.15) K. Derived excess properties, except excess viscosities (Δη), are found to be negative over the entire composition range. The addition of 1-MPZ reduces drastically the surface tension of water. The temperature dependence of surface tensions is explained in terms of surface entropy (S^S) and enthalpy (H^S). The measured and derived properties are used to probe the microscopic liquid structure of the bulk and surface of the aqueous amine solutions.