Absence Of Sodium Dodecyl Sulfate Research Articles

A bifunctional Zn(II) coordination polymer for fluorescence recognition towards hazardous matters and its high adsorption removal of dye pollutant

In this work, a novel Zn(II) coordination polymer (denoted as Zn-CP) was constructed by the mixed ligands of 6-(3′,4′-Dicarboxy phenoxy)isophthalic acid (H4L) and 4,4′-bis(imidazolyl)biphenyl (bib) under solvothermal method. And based on the Zn-CP, the surfactant agent sodium dodecyl sulfate (SDS) was further introduced into the structure, thus obtaining the Zn-CP(S) which possessed the same phase but a smaller size compared with the Zn-CP. Interestingly, the Zn-CP(S) presented a significantly ameliorated fluorescent intensity, about 4.36 times higher than that of the Zn-CP prepared in the absence of SDS. Taking advantage of the improved fluorescence trait of the Zn-CP(S), a fluorescence recognition towards hazardous matters was further carried out. The results showed that Zn-CP(S) could simultaneously recognized for Hg2+, Cr2O72− and a broad range of hazard nitroaromatic explosives with the satisfactory limits of detection (LODs). In addition, Zn-CP could also be used as a recyclable adsorbent to remove methyl orange (MO) in aqueous medium. The maximum equilibrium adsorption capacity of Zn-CP for MO was 61.01 mg/g, and the adsorption mechanism could be attributed to the weak inter-molecular interaction involved π-π stacking and hydrogen bonding between Zn-CP and the MO molecule. Therefore, the bifunctional material has potential application prospects in fluorescence recognition and adsorption.

Oxidation of Ethanolamine by Potassium Permanganate in the Presence and Absence of Sodium Dodecyl Sulphate: A Kinetic Study in an Acidic Medium

Oxidation of Ethanolamine by Potassium Permanganate in the Presence and Absence of Sodium Dodecyl Sulphate: A Kinetic Study in an Acidic Medium

Antiviral peptides inhibiting the main protease of SARS-CoV-2 investigated by computational screening and in vitro protease assay.

The main protease (Mpro) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) plays an important role in viral replication and transcription and received great attention as a vital target for drug/peptide development. Therapeutic agents such as small-molecule drugs or peptides that interact with the Cys-His present in the catalytic site of Mpro are an efficient way to inhibit the protease. Although several emergency-approved vaccines showed good efficacy and drastically dropped the infection rate, evolving variants are still infecting and killing millions of people globally. While a small-molecule drug (Paxlovid) received emergency approval, small-molecule drugs have low target specificity and higher toxicity. Besides small-molecule drugs, peptide therapeutics are thus gaining increasing popularity as they are easy to synthesize and highly selective and have limited side effects. In this study, we investigated the therapeutic value of 67 peptides targeting Mpro using molecular docking. Subsequently, molecular dynamics (MD) simulations were implemented on eight protein-peptide complexes to obtain molecular-level information on the interaction between these peptides and the Mpro active site, which revealed that temporin L, indolicidin, and lymphocytic choriomeningitis virus (LCMV) GP1 are the best candidates in terms of stability, interaction, and structural compactness. These peptides were synthesized using the solid-phase peptide synthesis protocol, purified by reversed-phase high-performance liquid chromatography (RP-HPLC), and authenticated by mass spectrometry (MS). The in vitro fluorometric Mpro activity assay was used to validate the computational results, where temporin L and indolicidin were observed to be very active against SARS-CoV-2 Mpro with IC50 values of 38.80 and 87.23 μM, respectively. A liquid chromatography-MS (LC-MS) assay was developed, and the IC50 value of temporin L was measured at 23.8 μM. The solution-state nuclear magnetic resonance (NMR) structure of temporin L was determined in the absence of sodium dodecyl sulfate (SDS) micelles and was compared to previous temporin structures. This combined investigation provides critical insights and assists us to further develop peptide inhibitors of SARS-CoV-2 Mpro through structural guided investigation.

Effect of Drinking Water Salt Content on the Interaction between Surfactants and Bacteria.

Sodium dodecyl sulfate (SDS) is a common surfactant used in various hygienic products. Its interactions with bacteria were studied previously, but the three-way interaction between surfactants, bacteria, and dissolved salts in the context of bacterial adhesion has not been studied. Here, we examined the combined effects of SDS (at concentrations typical of everyday hygienic activities) and salts, sodium chloride, and calcium chloride (at concentrations typically found in tap water) on the adhesion behavior of the common opportunistic pathogen Pseudomonas aeruginosa. We found that bacterial adhesion in the absence of SDS was dependent on the cation concentration rather than the total ionic strength and that combined treatment with several millimolar NaCl and SDS can increase bacterial adhesion. The addition of low concentrations of SDS (2 mM) to tens to hundreds millimolar concentrations of NaCl, typical of systems that suffer seawater incursion, reduced bacterial adhesion dramatically. Combined treatment with Ca+2 (in concentrations typical of those found in hard water) and SDS produced a small increase in total adhesion but a dramatic increase in the strength of adhesion. We conclude that the type and concentration of salts in water can have a considerable effect on the efficacy of soap in reducing bacterial adhesion and should be taken under consideration in critical applications. IMPORTANCE Surface-adhering bacteria are a reoccurring problem in many settings, including households, municipal water systems, food production facilities, and hospitals. Surfactants, and specifically sodium dodecyl sulfate (also known as SDS/SLS), are commonly used to remove bacterial contamination, but data regarding the interaction of SDS with bacteria and especially the effects of water-dissolved salts on this interaction are lacking. Here, we show that calcium and sodium ions can dramatically affect the efficacy of SDS on bacterial adhesion behavior and conclude that salt concentrations and ion species in the water supply should be considered in SDS applications.

SDS-induced hexameric oligomerization of myotoxin-II from Bothrops asper assessed by sedimentation velocity and nuclear magnetic resonance.

We report the solution behavior, oligomerization state, and structural details of myotoxin-II purified from the venom of Bothrops asper in the presence and absence of sodium dodecyl sulfate (SDS) and multiple lipids, as examined by analytical ultracentrifugation and nuclear magnetic resonance. Molecular functional and structural details of the myotoxic mechanism of group II Lys-49 phospholipase A2 homologues have been only partially elucidated so far, and conflicting observations have been reported in the literature regarding the monomeric vs. oligomeric state of these toxins in solution. We observed the formation of a stable and discrete, hexameric form of myotoxin-II, but only in the presence of small amounts of SDS. In SDS-free medium, myotoxin-II was insensitive to mass action and remained monomeric at all concentrations examined (up to 3mg/ml, 218.2μM). At SDS concentrations above the critical micelle concentration, only dimers and trimers were observed, and at intermediate SDS concentrations, aggregates larger than hexamers were observed. We found that the amount of SDS required to form a stable hexamer varies with protein concentration, suggesting the need for a precise stoichiometry of free SDS molecules. The discovery of a stable hexameric species in the presence of a phospholipid mimetic suggests a possible physiological role for this oligomeric form, and may shed light on the poorly understood membrane-disrupting mechanism of this myotoxic protein class.

Time-Resolved Small-Angle X-ray Scattering Studies during the Aqueous Emulsion Polymerization of Methyl Methacrylate.

Recently, we reported time-resolved synchrotron small-angle X-ray scattering (TR-SAXS) studies during aqueous emulsion polymerization using a bespoke stirrable reaction cell (J. Am. Chem. Soc. 2021, 143, 1474-1484). This proof-of-concept study utilized a semifluorinated specialty monomer (2,2,2-trifluoroethyl methacrylate) to ensure high X-ray contrast relative to water. Herein, we extend this approach to emulsion polymerization of methyl methacrylate (MMA) in the presence or absence of sodium dodecyl sulfate (SDS) at 70 °C. Solution conductivity measurements for this anionic surfactant indicated a critical micelle concentration (CMC) of 10.9 mM at this temperature. Thus, SDS was employed at either 1.0 or 20.0 mM, which corresponds to well below or well above its CMC. Postmortem analysis by 1H NMR spectroscopy indicated MMA conversions of 93-95% for these three formulations. We demonstrate that the X-ray contrast between water and PMMA is sufficiently large to produce high-quality scattering patterns during TR-SAXS experiments. Such patterns were fitted using a hard-sphere scattering model to monitor the evolution in particle diameter. This enabled (i) determination of the time point for the onset of nucleation and (ii) the evolution in particle size to be monitored during the MMA polymerization. The final particle diameters obtained from such TR-SAXS studies were consistent with postmortem DLS analyses, while TEM studies confirmed that near-monodisperse latex particles were formed. Micellar nucleation occurs within just 2 min when the SDS concentration is well above its CMC, resulting in a high particle number concentration and relatively small latex particles. In contrast, when SDS is either absent or present below its CMC, particle nuclei are formed by homogeneous nucleation over significantly longer time scales (14-15 min). In the latter case, adsorption of SDS onto nascent particles reduces their coagulation, giving rise to a larger number of smaller particles compared to the surfactant-free polymerization. However, the characteristic time required for the onset of nucleation is barely affected because this is mainly controlled by the kinetics of homogeneous polymerization of the relatively water-soluble MMA monomer within the aqueous phase. These results suggest that the aqueous emulsion polymerization of several other (meth)acrylic monomers, and perhaps also vinyl acetate, may be amenable to TR-SAXS studies.

Effect of sodium dodecyl sulfate on shape‐memory properties of side‐chain crystalline hydrogel via micellar copolymerization

AbstractA chemical shape‐memory hydrogel containing crystalline structure is prepared via micellar copolymerization of hydrophilic monomer acrylamide (AM) and hydrophobic monomer octadecyl acrylate (C18) in a sodium dodecyl sulfate (SDS) solution. The influence of SDS on the shape‐memory behavior of hydrogel investigated by differential scanning calorimetry (DSC) and Temperature‐dependent X‐ray indicate that the melting and crystallization peaks derived from the thermal properties of C18 units is different from peaks corresponding to the pure SDS. In addition, the microstructure evolution information of hydrogels dose not change upon heating process, regardless of the presence or absence of SDS. Therefore, only the hydrophobic associations formed by C18 blocks play a decisive role in the shape memory function of hydrogel system. The difference between the transition process (from temporary shape to permanent shape) of hydrogel with and without SDS at different temperature is because that the hydrophobic region of side chain crystallization of SDS‐free hydrogel may escape the restriction of SDS and become more sensitive to temperature, they can preferentially return to their initial shape under the same time and temperature than SDS‐containing gels. Whether SDS exists only affect the speed of shape memory behavior, but not the microstructure evolution of hydrogel system.

Electrochemical deposition of leaf stalk-shaped polyaniline doped with sodium dodecyl sulfate on aluminum and its use as a novel type of current collector in lithium ion batteries

A cyclic voltammetry (CV) method employing a solution containing H2SO4, aniline and sodium dodecyl sulfate (SDS) as the electrolyte solution was utilized to prepare a SDS-doped polyaniline (PANI) film onto the surface of the commercial aluminum (Al) foil at room temperature generating a novel current collector of SDS-PANI coated Al (denoted as SP/Al). The SDS-doped PANI films prepared in the presence of 2 mM, 5 mM and 10 mM SDS were, respectively, nominated as film SP-2, SP-5 and SP-10. As shown by the SEM images, many irregular particles covered with numerous protuberances were prepared in the absence of SDS, and very interestingly, in the presence of SDS, leaf stalk-shaped particles were fabricated on the surface of the commercial Al foil. As indicated by XRD and FTIR results, the main component of the leaf stalk-shaped particles was PANI. Most important of all, the initial discharge capacities of the commercial LiFePO4 (abbreviated as LFP) on the novel current collectors of SP/Al at 0.2 C were all remarkably higher than that of LFP on the commercial Al foil. Particularly, even at 5 C after 10 cycles, the average discharge capacity of LFP on SP-5/Al (65 mA h g−1) was still about 30% larger than that on the traditional Al foil (50 mA h g−1). Presenting the fact, that using the SDS-doped PANI film coated Al foil to replace the conventional Al foil was a feasible way to promote the electrochemical performance of LFP, is the main dedication of this preliminary work.

Deciphering the Kinetic Study of Sodium Dodecyl Sulfate on Ag Nanoparticle Synthesis Using Cassia siamea Flower Extract as a Reducing Agent.

Silver nanoparticles (Ag NPs) were synthesized using Cassia siamea flower petal extract (CSFE) as a reducing agent for the first time. In its presence and absence, the correlative effects of the anionic surface-active agent sodium dodecyl sulfate (SDS) were studied with respect to the development and texture of Ag NPs. Under different reagent compositions, the Ag NPs were inferred by localized surface plasmon resonance peaks between 419 and 455 nm. In the absence of SDS, there was a small eminence at 290 and around 350 nm, pointing toward the possibility of irregular polytope Ag NPs, which was confirmed in the transmission electron microscopy images. This elevation vanished beyond the cmc of [SDS], resulting in spherical and oval shaped Ag NPs. The effects of reagent concentrations were studied at 25 °C and around 7 and 9 pH in the absence and presence of SDS, respectively. Also, kinetic studies were performed by UV–visible spectrophotometry. Prodigious effects on shape and size were found under different synthesis conditions in terms of hexagonal, rod-, irregular-, and spherical shaped Ag NPs. Furthermore, the antimycotic activity of the synthesized Ag NPs was established on different Candida strains, and best results were found pertaining Candida tropicalis. The ensuing study impels the control of texture and dispersity for Ag NPs by CSFE and SDS, and the resultant polytope Ag NPs could be a future solution for drug-resistant pathogenic fungi.

Bed expansion and gas holdup characteristics of bubble–assisted fluidization of liquid–particle suspensions in a HydroFloat cell

The HydroFloat cells made by Eriez are designed for floating coarse particles using fluidization involving bubble–liquid–particle suspensions. The operational optimization and control of these cells can be a challenging task and require various correlations that are difficult to establish by theory. Here, experiments were performed to study the effect of SDS (sodium dodecyl sulfate) on the liquid–particle and bubble–liquid–particle fluidization processes in a laboratory-scale HydroFloat cell. Air was supplied to a perforated circular tube at the bottom to generate the bubbles while irregular coarse quartz particles were fed to the top by a vibrating plate as the solid phase. In the liquid–particle fluidization, the bed expansion (BE) increased with increasing superficial liquid velocity and agreed with the modified Richardson-Zaki equation (within 4% relative error). BE decreased to 12.5% in the presence of SDS at low concentrations. In the bubble–liquid–particle fluidization, BE was reduced by 8.46 – 2.89% and 15.1% with increasing superficial gas velocity and decreasing superficial liquid velocity in the absence of SDS, respectively. In the presence of SDS, BE increased with increasing superficial gas and liquid velocities. High SDS concentrations generated expanded beds with higher heights. Low SDS concentration (0.2 mM) increased the gas holdups by an average of 20% with increasing superficial gas velocity from 1.1 to 3.4 mm/s. Both BE and gas holdup were compared with the available empirical correlations. The estimated BE showed smaller mean absolute relative errors (MAREs) in the absence of SDS than the presence of SDS, while gas holdups yielded large MAREs. The particle sphericity and bubble Reynolds number were incorporated into the Begovich-Watson and Ramesh-Murugesan equations to estimate the BE and gas holdup, respectively. The modified equations significantly improved the predictions. The empirical correlations developed and investigated here would be useful for the operational optimization of the fluidized bed HydroFloat cells.

Redox-Initiated Reversible Addition-Fragmentation Chain Transfer (RAFT) Miniemulsion Polymerization of Styrene using PPEGMA-Based Macro-RAFT Agent.

Redox-initiated reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerizations are successfully conducted with an employment of trithiocarbonate-based macro-RAFT agents and surfactant. Two macro-RAFT agents-hydrophilic poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMA27 ) and amphiphilic poly(poly(ethylene glycol) methyl ether methacrylate)-b-polystyrene (PPEGMA27 -b-PS33 )- are examined for the miniemulsion polymerization of styrene. The use of PPEGMA27 (in the presence of sodium dodecyl sulfate (SDS)) results in a slow polymerization rate with a broad particle size. In the absence of SDS, the use of PPEGMA27 -b-PS33 results in a broad particle size distribution due to its inability to form uniform initial droplets whereas the same amphiphilic block copolymer in the presence of SDS yields resulting products with a uniform particle size distribution. The latter exhibits a fashion of controlled polymerization with a high consumption of monomer (98% in 100min) and a narrow molecular weight distribution throughout the polymerization. This is attributed to the formation of uniform droplets facilitated by SDS in a miniemulsion. The amphiphilic macro-RAFT agent is able to anchor efficiently on the monomer droplet or particle/water interface and form stabilized particles of well-defined PPEGMA27 -b-PS block copolymer, confirmed using dynamic light scattering and transmission electron micrographs.

The effect of sodium dodecyl sulfate concentration on the aggregation behavior of Aβ (1–42) peptide: Molecular dynamics simulation approach

Beta-amyloid (1–42) is the most effective peptide in the formation of inter-synaptic aggregate structures. These complex structures lead to disruption of the neural network and the development of Alzheimer's disease. Here, the effect of sodium dodecyl sulfate concentration on Aβ (1–42) structure has been investigated by molecular dynamics simulation. The calculations were performed at concentrations lower than and above than the critical micelle concentration. Two single and six peptide systems were used for each concentration. Calculations were also repeated in the absence of sodium dodecyl sulfate. The secondary structure of Aβ (1–42) was calculated in the designed systems. The results showed that the dominant secondary structure in monomeric systems is the helix. Also, the calculation of the Aβ (1–42) secondary structure shows that the behavior of the peptides is heterogeneous in the hexamer systems. The length of the Lys28-Ala42 salt bridge was calculated in different systems as criterion of peptide toxicity. The results showed that the length of the salt bridge is increased at both SDS concentrations. The radial distribution function was used to investigate the interaction of the peptide with SDS. The result revealed that the distribution of SDS molecules around the amyloid-β peptide residues is great in the presence of low SDS concentration. Also, the interaction intensity between the peptide and SDS at low SDS concentrations is higher than that at high SDS concentration.

Effects of additives on the morphology and stability of PbO2 films electrodeposited on nickel substrate for light weight lead-acid battery application

Abstract This work investigated the effects of NaF and sodium dodecyl sulfate (SDS) on the morphology and stability of electrodeposited PbO2 film. The PbO2 electrodeposition was conducted on the Ni-substrate by galvanostatic anodic deposition in acidic Pb(NO3)2 solution to be employed as a positive electrode in the lightweight lead-acid battery. The stability and electrochemical properties of the film were investigated by cyclic voltammetry in 4.7 mol L−1 H2SO4. Phase constituents and microstructures of the deposited PbO2 before and after cycling was characterized using atomic force microscope (AFM), scanning electron microscope (SEM), and X-ray diffraction spectroscopy. Experimental results show that current density and the concentration of Pb(NO3)2 and NaF positively affected the current efficiency for PbO2 deposition. A mixed-phase (ɑ-PbO2 and β-PbO2), relatively less stable (persist up to 80 cycles) and larger-grained deposit with low charge-discharge density was produced in the absence of SDS. The addition of a small amount of SDS in the electrolyte increased the proportion of β-PbO2 having compact and small-grained crystals resulting in the improvement of the stability (persist up to 300 cycles) and charge-discharge density of the PbO2 film in the battery environment. The density functional theory (DFT) calculation confirmed that the higher binding energy of H2O to the defected PbO2 sites caused by high cycling was mainly responsible for enormous oxygen evolution which eventually resulted in the failure of the positive electrode and water loss of the battery during operation.

Features of self-organization of sodium dodecyl sulfate in water-ethanol solutions: Theory and vibrational spectroscopy

In this work, experimental and theoretical studies of the micelle formation processes of sodium dodecyl sulfate in water-ethanol solutions with different ethanol content - 0% by volume, 8% by volume, 15% by volume, 30% by volume were carried out. For the first time, the manifestation in the vibrational spectra of the features of self-organization of sodium dodecyl sulfate (SDS) molecules in water-ethanol solutions was found. In the studied concentration ranges of ethanol and SDS it was found that in the presence of SDS, the strengthening of hydrogen bonds in solutions is observed in a wider range of changes in the concentration of ethanol than in the absence of SDS. The behavior of the band at 1060 cm−1 at low concentrations of ethanol (8%) indicates the dual behavior of ethanol molecules as a co-surfactant and co-solvent in the process of micelle formation. The obtained experimental data are confirmed by theoretical calculations. For the first time, a contactless express method was proposed for determining the critical micelle concentration of SDS in water-ethanol solutions with different ethanol content from Raman spectra. The measured values of SDS critical micelle concentration are in good agreement with the literature data.

Experimental and theoretical approaches on the reaction mechanism and kinetics of dimethyl 2-(6-oxopyridazin-1(6H)-yl)fumarate: Micelle and salt effects

A one-pot diastereospecific reaction between DMAD (dimethyl acetylenedicarboxylate) (1) and 3-(2H) pyridazinone (2) in the presence of AsPh3 (3) as an efficient catalyst was studied kinetically. The effect of different salts was considered on the reaction velocity in methanol. The results highlighted that NaBr and CaCl2 salts – in 5 × 10−2 M and 10−2 M concentrations, respectively – raised the reaction rate near four times. Sodium dodecyl sulfate (SDS) as an anionic micelle was added to the solution, and the reaction rate decreased by half. The first and second steps (k1 and k2) of the reaction mechanism become observable in the UV – Vis spectrum when SDS was added to the reaction medium, this observation creates new information regarding the reaction mechanism. Activation energy and its related parameters were determined for the reaction, hence associative mechanism, chemically and enthalpy-controlled being of the reaction documented. A computational study was carried out (for the reaction in the absence of SDS) employing DFT method at the B3LYP/6-31 + G(2d,p) level of theory and fourth step, approved as RDS (rate determining step). Job’s method was used to determine the stoichiometry ratio among the reactants (1), (2) and (3) and the relevant plot exhibited the 1:1:1 stoichiometric ratio.

Electron beam irradiation synthesis of porous and non-porous pectin based hydrogels for a tetracycline drug delivery system

Electron beam irradiation was used for the synthesize of porous and non-porous pectin based hydrogels through conjugation of pectin with 5-hydroxytryptophan in the presence and absence of sodium dodecyl sulfate, respectively. The hydrogels were characterized by different methods. Tetracycline hydrochloride was loaded on the hydrogels by swelling equilibrium method and its release in different media was studied. The effect of SDS amount and electron beam irradiation dose on the swelling, drug loading, drug release, gel content, and mechanical properties were investigated. The release of drug form both hydrogels followed non-Fickian diffusion mechanism and was best fitted with the Korsmeyer-Peppas model. In vitro, drug release studies revealed that the release of drug from non-porous hydrogel is relatively slow while its release from porous hydrogel occurs with higher amounts and faster rate. Biocompatibility and cytotoxic analysis indicate that the prepared hydrogels dressing are non-thrombogenic, non-hemolytic and non-toxic. Furthermore, acceptable bacteria growth inhibition against Escherichia coli and Staphylococcus aureus were observed for both drug-loaded hydrogels. Thus, these hydrogels are suitable for the application of an antibacterial wound dressing.

Millimolar concentration of sodium dodecyl sulfate inhibit thermal aggregation in hen egg white lysozyme via increased α-helicity

The objective of this study was to assess the effects of sodium dodecyl sulphate (SDS) on the hen egg white lysozyme (HEWL) at pH 9.0. We employed several spectroscopic (light scattering, intrinsic fluorescence, dynamic light scattering (DLS), and circular dichroism (CD)) techniques to evaluate the role of SDS in prevention of aggregation and imparting stability to HEWL. From the spectroscopic measurements, it was observed that the secondary as well as tertiary structures were modified in the presence of SDS. Thermal stability of HEWL with or without SDS was also evaluated. In the absence of SDS, HEWL starts unfolding at transition temperature 54.0 ± 0.22 °C. However, in the presence of 2.0 mM SDS, the HEWL unfolded at slightly higher temperature, and transition temperature was found to be around 59.77 ± 0.27 °C. In this study, we also found that thermal unfolding of HEWL led to simultaneous aggregation at temperatures above 55 °C as confirmed by light scattering measurements but no aggregation was seen in the presence of SDS. In the absence of SDS, the hydrodynamic radii of HEWL increased at higher temperature. However, the hydrodynamic radii remained unchanged in the presence of SDS up to 90 °C. The overall results suggested that SDS provided extra stability to and simultaneously prevented aggregation of HEWL. The possible interactions found in SDS-stabilized HEWL are electrostatic and hydrophobic.

Insights on the interaction between sodium dodecyl sulfate and partially hydrolyzed microblock hydrophobically associating polyacrylamides in different polymer concentration regimes

The partially hydrolyzed microblock hydrophobically associating polyacrylamides (HMBHAPs) with different microblock lengths (NH) and some positive charges were prepared by free radical copolymerization in aqueous solution and the HMBHAPs were characterized by FTIR, 1H-NMR, ion titration, elemental analysis and thermal gravimetric analysis. Moreover, the hydrodynamic size and microtopography of HMBHAPs were also characterized by dynamic light scattering and environment scanning electron microscope. The self-association effect of HMBHAPs and the interaction between HMBHAPs and oppositely charged sodium dodecyl sulfate (SDS) in different polymer concentration regimes were investigated through the measurements involving rheology, fluorescence, conductivity and zeta potential. The results show that HMBHAPs presented different viscosity behaviors in the concentration range concerned that could be divided into three different concentration regimes, where the viscosity contribution made by association effect was significantly discrepant and enhanced with increasing microblock length. Moreover, rheological measurements indicate that, with the addition of SDS, zero-shear viscosity (η0) of HMBHAPs presented different variation trends in three polymer concentration regimes: at lower HMBHAPs concentration, the η0 of HMBHAPs/SDS system was smaller than that in absence of SDS; at moderate HMBHAPs concentration, the system viscosity increased slightly; whereas, the viscosity distinctly increased with increasing SDS concentration at higher HMBHAPs concentration. The I3/I1 and Ie/Im also demonstrated that the aforementioned viscosity behaviors were closely related to the efficiency and number of the associations, as well as the micro-block longer the association effect stronger. In addition, η0 and Ie/Im exhibited a very interesting “double peaks” phenomenon with increasing SDS, which may be interpreted by the simultaneous influence of electrostatic interaction and the association effect between cationic hydrophobic groups and anionic surfactant. The SDS amounts binded by HMBHAPs showed a slightly increasing trend as increasing polymer concentration and decreasing NH. Zeta potentials at n-octane-water interface showed a “charge reversal” phenomenon with increasing HMBHAPs concentration, which appeared earlier for longer microblock. With the addition of SDS, Zeta potential rapidly varied from an initial smaller positive charge to a greater negative charge, and the variation presented earlier with varied polymer concentration regimes and increasing NH. This result may be ascribed to the adsorption of HMBHAPs macromolecules at the oil-water interface and different inter-molecular conformations after interacting with SDS at the interface.

Sodium Dodecyl Sulfate Preferentially Promotes Enclathration of Methane in Mixed Methane-Tetrahydrofuran Hydrates

SummaryMethane storage in mixed hydrates is advantageous due to faster kinetics and added stability. However, capacity needs to be improved. Here we study mixed hydrates of methane (CH4) and tetrahydrofuran (THF), in the presence of sodium dodecyl sulfate (SDS) as a kinetic promoter for hydrate formation. We report the co-existence of pure methane (sI) and mixed CH4-THF hydrates (sII) in the presence of SDS; however, in the absence of SDS, co-existence of pure THF (sII) and mixed CH4-THF hydrates (sII) was observed. Thus the presence of SDS preferentially promotes the enclathration of methane over that of THF. Furthermore, through in situ Raman spectrometry, complemented by high-pressure differential scanning calorimeter, we present temperature-dependent methane occupancy in small and large cages of sI and sII hydrates. Our findings offer new insights for enhancing the methane storage capacity in more stable sII hydrate configuration for large-scale methane storage via solidified natural gas technology.

Organic Surfactants Protect Dissolved Aerosol Components against Heterogeneous Oxidation.

Oxidative aging alters the composition of organic aerosols over time, in turn affecting the ability of aerosols to seed cloud formation and scatter solar radiation. Here we explore the heterogeneous photooxidation of model organic particles with and without a soluble surfactant coating. Tricarballylic acid (TCA), a proxy for α-pinene oxidation products, serves as a representative small organic solute. Sodium dodecyl sulfate (SDS) was selected as the representative soluble surfactant because its surface properties have been extensively characterized. A flow reactor and aerosol mass spectrometer were used to determine the second-order reaction rate constant ( k = (1.9 ± 0.1) × 10-11 cm3 molecule-1 s-1) and reactive uptake coefficient (γ = 3.0) for the heterogeneous photooxidation of uncoated TCA particles by gas-phase OH radicals; such a high uptake coefficient implicates radical chain reactions in the oxidation mechanism. SDS dramatically slows the disappearance of TCA: when the SDS concentration approaches monolayer coverage, the rate of reaction of TCA with OH decreases by ∼60% relative to the rate in the absence of SDS. These results indicate that small concentrations of surface-active molecules on atmospheric particles can protect organic solutes in the bulk from oxidative aging. This effect extends the environmental lifetime of dissolved pollutants.