Studies on properties of softwood (Ficus hispida)/PMMA nanocomposites reinforced with polymerizable surfactant-modified nanoclay

Soft wood (Ficus hispida) was chemically modified by impregnation of methyl methacrylate monomer, glycidyl methacrylate (GMA), a cross-linking agent, and montmorillonite (MMT) using catalyst heat treatment. MMT was modified by using a polymerizable surfactant 2-acryloloxy ethyl trimethyl ammonium chloride (ATAC) and a mixture of surfactants ATAC and cetyl trimethyl ammonium bromide (CTAB) in a molar ratio of (1:1). A comparative study on different properties of the prepared wood polymer nanocomposite (WPNC) based on impregnation of intercalating mixture containing MMA/GMA/clay modified by both the surfactants (ATAC and CTAB) and MMA/GMA/clay modified by only surfactant ATAC were done. FTIR, XRD, and TGA studies were employed for the characterization of clay and WPNC. WPNC prepared by using combined surfactant-modified clay along with MMA/GMA exhibited improved dimensional stability, chemical resistance, thermal stability, mechanical properties, and lower water uptake than that of WPNC prepared by using single surfactant-modified clay and MMA/GMA system.     

A Study on Dispersion and Antibacterial Activity of Functionalizing Multi‐walled Carbon Nanotubes with Mixed Surfactant

The dispersibility in aqueous phase and antibacterial activity of multi‐walled carbon nanotubes (MWNT) with mixed surfactant functionalization has been studied. The ratio of 3:7 between hexadecyltrimethylammonium bromide and octylphenol ethoxylate (TX100) showed the highest dispersing power for MWNT. The use of mixed surfactants formed stable MWNT dispersions at lower total surfactant concentration compared to their concentrations when used alone. UV–Vis spectroscopy, transmission electron microscopy and Fourier transform infrared spectroscopy were employed to characterize the dispersion of MWNT in the aqueous phase. The result indicated that the surfactant molecules had been successfully adsorbed onto the surface of the MWNT. Bacterial toxicity assay showed that the mixed surfactant‐functionalized MWNT had a strong antibacterial activity and concentration dependence to Staphylococcus aureus. Based on the consideration of the cost and environmental impact, the use of mixed surfactant (CTAB‐TX100) should be more favorable for the stable dispersion of MWNT and the improvement of antibacterial activity than that of an individual surfactant. These observations suggested that the mixed surfactant‐functionalized MWNT might be a promising antibacterial agent for removal and inactivation of biological contaminants in water treatment applications.     

Wetting and adsorption properties of cetyltrimethylammonium bromide and Triton X-100 mixture with short-chain alcohol in polymer–solution–air system

Measurements of the contact angle of the aqueous solutions of Triton X-100 (TX-100) and cetyltrimethylammonium bromide (CTAB) mixture with methanol or propanol on the polytetrafluoroethylene (PTFE) and nylon-6 surfaces were made. On the basis of the obtained results, the Gibbs surface excess concentration of alcohol and TX-100 + CTAB mixture at the polymer–solution and polymer–air interfaces was calculated and compared to that at the solution–air one. The standard Gibbs free energy of alcohol adsorption was determined by different methods. For TX-100 and CTAB mixture, this energy was calculated using the values of critical micelle concentration (CMC) of that mixture, the surface tension and contact angle of aqueous solution of alcohol as well as the surface tension and contact angle of the aqueous solution of TX-100 and CTAB mixture with alcohol at CMC. The polymer–solution interfacial tension, the adhesion tension, and the adhesion work of the studied solutions to the polymer surface were also determined. From the obtained data, it results that the studied solutions can wet completely only the nylon-6 surface and that below alcohol critical aggregation concentration the adsorption of surfactants and alcohols at the polymer–water and water–air interfaces is similar for PTFE and different for nylon-6.     

Effects of three surfactant types of anionic, cationic and non-ionic on tensile properties and fracture surface morphology of epoxy/MWCNT nanocomposites

Three types of surfactants were used to enhance the dispersion of multi-wall carbon nanotubes (MWCNTs) in the epoxy matrix. MWCNTs were separately treated with non-ionic (polyoxyethylene octyl phenyl ether, Triton X-100), cationic (hexadecyl-trimethyl-ammonium bromide, CTAB) and anionic (sodium dodecyl sulfate, SDS) surfactants and their effects were evaluated on the dispersion state and surface chemistry, as well as on the tensile properties and tensile fracture surface morphology of MWCNTs/epoxy nanocomposites. The active surfaces of the carbon nanotubes were characterized by FTIR. The non-ionic surfactant, Triton X-100, had the best effect on dispersion of the MWCNT in the epoxy matrix, thus, positively affecting the tensile parameters of the corresponding nanocomposites which were attributed to the ??bridging?? effects between the MWCNT and epoxy, introduced by the hydrophobic and hydrophilic heads of the corresponding surfactant. Presence of MWCNTs as reinforcing agent increased the elastic modulus of nanocomposites, indicating the improved interfacial adhesion between CNTs and polymer matrix. The regions of nucleation and propagation of cracks were clearly seen in the SEM micrographs of the tensile fracture surface of the nanocomposites. The cracks deviated on reaching the carbon nanotubes. The dispersing aiding capabilities of the three surfactants used in the present study were as follows: cationic?<?anionic?<?non-ionic.     

Surfactant-Induced Wettability Alteration of Oil-Wet Sandstone Surface: Mechanisms and Its Effect on Oil Recovery

Different analytical methods were utilized to investigate the mechanisms for wettability alteration of oil-wet sandstone surfaces induced by different surfactants and the effect of reservoir wettability on oil recovery. The cationic surfactant cetyltrimethylammonium bromide (CTAB) is more effective than the nonionic surfactant octylphenol ethoxylate (TX-100) and the anionic surfactant sodium laureth sulfate (POE(1)) in altering the wettability of oil-wet sandstone surfaces. The cationic surfactant CTAB was able to desorb negatively charged carboxylates of crude oil from the solid surface in an irreversible way by the formation of ion pairs. For the nonionic surfactant TX-100 and the anionic surfactant POE(1), the wettability of oil-wet sandstone surfaces is changed by the adsorption of surfactants on the solid surface. The different surfactants were added into water to vary the core surface wettability, while maintaining a constant interfacial tension. The more water-wet core showed a higher oil recovery by spontaneous imbibition. The neutral wetting micromodel showed the highest oil recovery by waterflooding and the oil-wet model showed the maximum residual oil saturation among all the models.     

Effect of surfactants on the thermodynamic properties of Methyl Orange dye in buffered solutions

The apparent thermodynamic parameters of ionisation and the association constants of the two forms of Methyl Orange were evaluated in the presence of different surfactants (TX-100 as nonionic, CTAB as cationic and SDS as anionic). The enthalpy of ionisation of the dye in aqueous solution and at different surfactant concentrations is obtained from a novel thermochromic method and is found to decrease in aqueous medium in CTAB and TX-100 micelles and to increase in the case of SDS micelles. The apparent ionisation constant of the dye is evaluated spectrophotometrically for each surfactant concentration and type. The apparent Gibbs free energy, entropy of ionisation and association constants are also calculated. The results are discussed in light of the stabilisation of the two forms of the dye in the micellar core of the different surfactants and their effect on properties of the bulk solution is examined.     

Bordeaux-R interactions with surfactants: thermochromic investigations of proton ionisation in cationic, nonionic and anionic surfactant solutions

Apparent thermodynamic parameters for the hydroxy proton ionisation of Bordeaux-R were obtained in micellar solutions using the thermochromic method. The effect of addition of the surfactants CTAB, TX-100 and SDS was investigated in buffered solutions in the pH range of 6–13. Ionisation constants in water and in the presence of surfactants were determined spectrophotometrically and the p K ' of Bordeaux-R in water was found to be 10.90 in the absence of surfactant. However, at concentrations above critical micelle concentration, p K ' dropped to 10.14 with CTAB, increased to 11.29 with TX-100 but was insensitive to SDS addition. Standard enthalpies and entropies of ionisation were obtained using the thermochromic method. This method, in conjunction with p K and spectral measurements and comparison with different azo dyes, has been shown to provide detailed information on the mechanism of dye–surfactant interaction.     

不同因素对CTAB/TX-100微乳液相图的影响

用ε-β"鱼状"相图法研究了阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)与非离子表面活性剂辛基苯酚聚氧乙烯(10)醚(TX-100)以不同摩尔比复配形成的CTAB/TX-100/醇/油/NaCl水溶液微乳液体系的相行为和增溶性能.结果表明,随着醇浓度的增加,体系由水包油型(O/W)(winsor Ⅰ or (2-)...     

Study of antibacterial properties of polypropylene filled with surfactant‐coated silver nanoparticles

Medical applications require, in most cases, antibacterial protection. The use of silver (Ag) gives important antibacterial properties since silver is highly toxic for bacteria. In this research work, we have used silver nanoparticles (Ag NPs) with different surfactants, polyvinyl pyrrolidone (PVP) and oleic acid (OA) to facilitate dispersion. PP‐Ag NPs compounds were prepared by melt mixing, and the effects of the processing conditions on nanoparticles' dispersion were investigated by transmission electron microscopy (TEM). The antibacterial efficiency of PP‐Ag NPs compounds against Staphylococcus aureus ATCC 6538 and Escherichia coli ATCC 8379 was evaluated. Results show that good dispersion is obtained with rotating speeds in the 350–500 rpm range. TEM analysis reveals balanced dispersion and presence of some Ag NPs aggregates. Regarding antimicrobial properties, the use of PVP as surfactant leads to “significant” antimicrobial activity of 1.5 against Staphylococcus aureus and Escherichia coli; on other hand, the use of oleic acid (OA) as surfactant leads to strong protection against Staphylococcus aureus (antimicrobial activity between 2.5 and 3.3) but the overall protection against Escherichia coli is very low (lower than 1). Results show that the use of surfactants for Ag NPs has important effects on antibacterial properties of polypropylene filled with coated Ag NPs. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Effect of non-ionic surfactants on thermomechanical properties of epoxy/multiwall carbon nanotubes composites

Epoxy/multiwall carbon nanotubes (MWCNTs) composites were investigated using three different non-ionic surfactants (BYK-110, Tween-80 and Nonidet-P40) separately as a modifier. The role of surfactants in dispersion of MWCNTs in the epoxy matrix was studied. Among three surfactants used, performance of Nonidet-P40 was found to be the best in improving the thermomechanical properties of the epoxy resin and achieving good dispersion of MWCNTs. The good dispersion of Nonidet-P40 modified MWCNT in the epoxy matrix is a result of the π–π interaction between π electrons of the Nonidet-P40 and π electron clouds of MWCNTs as well as H-bonding interaction between of Nonidet-P40 and the epoxy matrix. This type of interaction does not disturb the π electron clouds of MWCNTs as opposed to chemical functionalization strategy.     

Investigation of Pt Catalysts Supported on Multi-Walled Carbon Nanotubes with Various Diameters and Lengths

Platinum electrocatalysts supported on multi-walled carbon nanotubes (MWCNTs) with various diameters and lengths were studied by using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) and Chronoamperometry. The results indicated that the MWCNTs with smaller diameter generated more amorphous carbon after a sonochemical oxidation treatment. Compared with the long MWCNTs, the short MWCNTs had more open ends, resulting in high-Pt dispersion and electrocatalytic activity towards methanol oxidation. Pt nanoparticles supported on short MWCNTs with a diameter of 30–50 nm exhibited the best Pt dispersion and highest methanol oxidation activity among the catalysts studied. The high activities of the catalysts based on short MWCNTs were due to both the intrinsic high activity of the ends of MWCNTs and a good Pt distribution.     

Antimicrobial and Cytotoxic Properties of Bisquaternary Ammonium Bromides of Different Spacer Length

A group of cationic gemini surfactants (bisquaternary ammonium bromides) with different spacer chain lengths (8–6–8, 8–7–8, 8–8–8, 8–9–8) was investigated, paying special attention to antimicrobial and the cytotoxic properties as well as their antimicrobial activity during long‐term storage. It was shown that the compounds investigated exhibit excellent antimicrobial activity against Gram‐positive bacteria (Staphylococcus aureus) and Gram‐negative bacteria (Pseudomonas aeruginosa) as well as antifungal properties (Candida albicans). The gemini surfactants tested had the differential level of cytotoxicity against normal lymphocytes. It was shown that the spacer chain length plays an important role in antibacterial activity and influences the cytotoxicity. The gemini surfactants with shorter spacer chain length, that had higher critical micelle concentration, showed generally weaker antibacterial properties, but on the other hand, these exhibited lower level of cytotoxicity. Furthermore, the aqueous solution of gemini surfactants exhibited the same antimicrobial activity even after 3 months.     

Effect of natural and synthetic surface coatings on the toxicity of multiwalled carbon nanotubes toward green algae

Ubiquitous dissolved organic matter (DOM) from various sources can interact with discharged multiwalled carbon nanotubes (MWCNTs) and pose distinct effects on the toxicity of MWCNTs to aquatic organisms. This study for the first time compared effects of a natural originated humic acid (HA) and two synthetic surfactants (sodium dodecylbenzenesulfonate – SDBS, octyl phenoxy polyethoxyethanol – TX100) on the toxicity of MWCNTs to a unicellular green alga (Chlorella pyrenoidosa). Algal growth inhibition, cell surface hydrophobicity, oxidative stress, MWCNT-cell agglomeration, and cell morphology change and internalization of MWCNTs were assayed to investigate individual and combined toxicities of MWCNTs and DOMs, and mechanisms underlying different effects of DOMs on the toxicity of MWCNTs were specifically addressed. It is shown that SDBS and TX100 were capable of promoting cell internalization of MWCNTs and triggering higher oxidative stress, and thereby increasing the toxicity of MWCNTs; while HA could alleviate the toxicity of MWCNTs through limiting cell internalization of MWCNTs and reducing oxidative stress. The outcomes of this work shed new light on the assessment of ecological toxicity of discharged nanomaterials.     

Synthesis of mechanically robust antimicrobial nanocomposites by click coupling of hyperbranched polyurethane and carbon nanotubes

This study demonstrates that mechanically robust antimicrobial nanocomposites of multiwalled carbon nanotubes (MWCNTs) and hyperbranched polyurethane (HBPU) can be prepared via a click chemistry reaction. Various compositions of HBPU-functionalized MWCNTs were synthesized from reactions of azide moiety-containing HBPU with alkyne-functionalized MWCNTs. The HBPU-functionalized MWCNTs were characterized morphologically using transmission electron microscopy and field emission scanning electron microscopy and chemically using Fourier transform infrared spectrometry, Raman spectroscopy, and X-ray photoelectron spectroscopy. The functionalized MWCNTs exhibited excellent dispersion in the HBPU matrix, and as a result, superior mechanical and strong antibacterial properties were obtained. The antimicrobial properties were examined by use of gram-negative bacteria Escherichia coli (E. coli). Consequently the click coupled bonding of MWCNTs with HBPU was very efficient for regulating the composite properties and achieving high performance materials.     

Effect of Ionic Head Group on Admicelle Formation by Polymerizable Surfactants

One of the problems of using surfactant-modified adsorbents in a surfactant-based adsorption process is loss of surfactant because of desorption. Recently, polymerizable surfactants have been used to minimize surfactant losses by polymerization of the surfactant admicellar structure to help secure it to the solid oxide surface. In this study, adsorption of polymerizable cationic gemini surfactant was used to form polymerized bilayers on silica. UV light was used to irradiate and initiate the polymerization process. Surfactant adsorption and desorption were evaluated to compare the efficiency of polymerized and non-polymerized surfactants using gemini and conventional surfactants, respectively. Results demonstrate that the increased stability of the polymerized surfactant-modified surface can reduce the desorption of surfactant from the surface, thereby improving operating characteristics of the surfactant-modified media (e.g., maintaining adsolubilization potential, dispersion stability, etc.).     

Effect of Dispersed Multi-Walled Carbon Nanotubes on Mixed Matrix Membrane for O2/N2 Separation

Mixed matrix membranes (MMMs) consisting of multiwalled carbon nanotubes (MWCNTs) embedded within polyetherimide were prepared. Surfactants of different charges were utilized to disperse the nanotubes through a simple non-covalent approach. The characterization results suggest that proper selection of the dispersing agent contributed to better dispersion of nanotubes. The MMMs exhibited improved thermal stability and mechanical strength, which indicate the improvement of dispersion and compatibility within the polymer matrix. The resulting membrane exhibited permeance improvement of O₂ and N₂ as much as 87.7% and 120% respectively compared to that of neat polyetherimide. The results implied that Triton-X100 treated MWCNTs is a promising filler to enhance gas permeability.     

Interfacial Dilational Rheology of Sodium Lauryl Glycine and Mixtures with Conventional Surfactants

Amino acid-based surfactants are environmentally friendly surfactants, which have aroused increasing interest. In the application of amino acid-based surfactants, they are often compounded with other kinds of surfactants to obtain formulations that meet certain requirements. Herein, sodium lauroyl glycinate (C12-Gly-Na) was selected as a representative amino acid-based surfactant to compound with an anionic surfactant (sodium dodecyl sulfate [SDS]), a cationic surfactant (dodecyl trimethyl ammonium Bromide), and a nonionic surfactant (Triton X-100: p-octyl polyethylene glycol phenyl ether). Surface tension measurements and interfacial dilational rheological experiments were performed to study the interfacial behaviors of C12-Gly-Na and its mixtures. The results show that mixture systems have better interfacial activity than individual C12-Gly-Na and there is an obvious synergy between C12-Gly-Na and C12TAB under strong electrostatic attraction. Thus, the C12-Gly-Na/C12TAB mixture shows lower critical micelle concentration (CMC) and γ_CMC and higher dilational modulus than the individual surfactants. Besides, the film formed by the C12-Gly-Na/C12TAB mixture has higher viscoelasticity than single C12-Gly-Na and its mixtures with SDS and TX-100. With the increase of bulk concentration, the dilational moduli of C12-Gly-Na, C12-Gly-Na/SDS, and C12-Gly-Na/TX-100 run through two maxima, while, due to stronger electrostatic attraction, only one maximum appears in the C12-Gly-Na/C12TAB system. The study of the interfacial properties of amino acid surfactant and its mixtures with other surfactants provides a theoretical foundation for potential applications in cosmetic, food processing, and daily chemical industries.     

Selection of surfactant-modified lipases for interesterification of triglyceride and fatty acid

Interesterification of tripalmitin and stearic acid inn-hexane was investigated with surfactant-modified lipases. Various kinds of lipases and surfactants were screened for high interesterification activity of the modified lipases. The modified-lipase hydrophile-lipophile balance value and fatty acid group of the surfactants. The modified lipase obtained fromRhizopus japonicus with sorbitan monostearate as surfactant had the highest activity in then-hexane system. The interesterification activity of the selected modified lipase in molten substrates at 75°C without solvents was the same as that in then-hexane system at 40°C.     

纳米Cu分散稳定性能影响因素及作用机理研究

鉴于粉体分散对纳米流体强化传热具有重要意义,通过测定纳米Cu-水悬浮液的Zeta电位和吸光度,探讨了不同pH值、不同分散剂种类及质量分数对纳米Cu-水悬浮液分散稳定性的影响,并分析其作用机理。结果表明:Zeta电位绝对值与吸光度有良好的对应关系,Zeta电位绝对值越高,吸光度越大,则体系分散稳定性越好;pH值、分散剂种类及加入量是影响纳米Cu-水悬浮液分散稳定性的主要因素。pH值为9.5左右时,体系Zeta电位绝对值和吸光度较高,相应分散稳定性较好。CTAB和SDBS能显著提高水溶液中Cu表面Zeta电位绝对值,增大了颗粒间静电排斥力,改善了悬浮液稳定性,而TX-10通过空间位阻在颗粒表面形成良好的水化膜,提高了Cu在水溶液中的分散稳定性。在质量分数为0.1%的纳米Cu-水悬浮液中,TX-10,CTAB,SDBS 3种分散剂加入质量分数分别为0.43%,0.05%,0.07%时,均能得到分散稳定的悬浮液体系。     

Effect of cefoperazone sodium on the physicochemical properties of surfactants

The effects of cefoperazone sodium (CS), a pharmaceutical compound, on the critical micelle concentration (CMC) of surfactants with different charges [cetyl trimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and Triton X-100], the cloud point of Triton X-100, and the Krafft temperatures of SDS and CTAB were studied. The interaction of CS with differently charged surfactants was determined by ultraviolet and fluorescence spectrophotometry. The results show that with increasing CS concentration, the Krafft temperature increases and the CMC decreases in the SDS/H₂O system, whereas the opposite results are obtained in the CTAB/H₂O system. Both the cloud point and the CMC of Triton X-100 increase with the addition of CS. The above results are attributed to the different micellar interactions between CS and surfactants with different charges.