Effect of electrolytes on the physicochemical behaviour of sodium dodecyl sulphate micelles

The values of the critical micelle concentration (cmc) and the degree of electrolytic micelle dissociation, a, for sodium dodecyl sulphate (SDS) as a function of the concentrations of the electrolytes added, NaCl, KCl, NaF, NaClO₄, NH₄ClO₄, and Mg(ClO₄)₂, have been determined. The values of the SDS cmc have been shown to depend on the kind and concentration of the electrolyte cations. The electrolyte cations cause a decrease of the cmc in the following order: Na⁺4⁺+2+. Moreover, a depends on the kind and concentration of the electrolyte added. The electrolyte anions have a much smaller effect on the values of a than the cations. The anions enhance a in the following order: F^->ClO₄^->Cl^-. The effect of different electrolyte cations on a is observed; moreover the values of a either increase or decrease with the electrolyte concentration. Other micellization parameters of SDS versus the concentration of the electrolytes added have been calculated.     

Synthesis and solution properties of comblike polymers from octadecyl methacrylate and acrylic acid

Amphiphilic polymers consisting of a statistical distribution of octadecyl methacrylate (ODMA) and acrylic acid in respective molar ratios of 83-22 and 17-78 mol% and in a molecular-weight range of 2.35-4.70᎒⁴ gmol^-1 have been synthesized. The series of polymers consisting of various mole fractions of ODMA and acrylic acid are expected to exhibit unique characteristics resembling ionomer to hydrophobically modified polyelectrolytes. The changes in the I₃/I₁ emission intensity ratios of pyrene, occurring in the presence of tetrahydrofuran (THF) solutions of the polymers have been taken as the main basis for inferring solution structures. The polymers are found to form random-coil to collapsed-coil/aggregated structures in THF solvent depending on the copolymer compositions. The polymer consisting of 83 mol% ODMA and 17 mol% acrylic acid behaves as an ionomer, capable of forming collapsed-coil structures at concentrations of 0.02 gml^-1 and above as shown by a very high I₃/I₁ of 1.20 (I₃/I₁ of pyrene in THF is 0.85). In contrast, the poly(octadecyl methacrylate) homopolymer and the sets of copolymers consisting of a very high proportion of acrylic acid to an extent of 73 mol% and above contribute to almost negligible or very small changes in I₃/I₁ similar to the homopolymer, poly(octadecyl methacrylate), suggesting the formation of random-coil structures.     

Inter- and intramolecular N-terminal methyl–side chain interactions in N-acetyl-L-glutamic acid oligomeric benzyl ester solutions. 1H NMR study

Oligomeric N-acetyl-L-glutamic acid benzyl esters with exact residue number (2, 3 or 4) have been synthesized by a stepwise procedure. The aggregational behavior of these oligomeric molecules in dioxane and benzene has been investigated by use of ¹H NMR. In particular, the concentration dependence of the ¹H signals for the N-terminal CH₃ protons has provided evidence that an intermolecular CH₃···? interaction plays a critical role in the formation of aggregates and that an intramolecular CH₃···? interaction occurs in the monomolecular state.     

Chemical deposition of copper sulfide films in the surface of polyamide by the use of higher polythionic acids

Films of copper sulfides of varying composition are formed in a surface matrix of polyamide by a sorption-diffusion method using solutions of higher polythionic acids, H₂S_nO₆ (n>6), as sulfuring agents. A film of nonstoichiometric Cu_xS (x=1.06-1.95) is obtained when the sulfured polyamide is treated with a solution of Cu(I-II) salt. The value of x in Cu_xS decreases with the prolongation of the period of polyamide sulfuration in the H₂S_nO₆ solution and increases with the prolongation of the period of sulfured polyamide interaction with the copper salt solution. The films obtained are formed from two main phases: yarrowite (Cu_1.12S) and anilite (Cu_1.75S). Depending on the polyamide sulfuration and the sulfured polyamide interaction with a solution of Cu(I-II) salt conditions, Cu_xS films on polyamide of different electrical conductivity were obtained. The sulfide with a composition close to CuS has the highest electrical conductivity.     

Fluorescence study of chromophore labeled strong polyelectrolyte bound with oppositely charged surfactant

Four strong polyelectrolyte samples of 2-(acrylamido)-2-methylpropanesulfonic acid (AMPS) and N,N-dimethylacrylamide (DMAA) were radically copolymerized with a single label of naphthalene or pyrene, with both labels and without label, containing about 40 mol % AMPS. Fluorescence nonradiative energy transfer (NRET) I_Py/I_Np, anisotropy r, I₁/I₃ and excimer emission I_E/I_M of pyrene labels were observed in dilute aqueous solutions with and without cationic surfactant of cetyltrimethylammonium bromide (CTAB). The overlap concentration was determined as 3 g/L from the appearance of intermolecular excimer. The variation of intra- and intermolecular NRET with total polyelectrolyte concentration showed that the charged chains preferentially interpenetrated each other rather than reduce their coil volume as their concentration beyond the overlap threshold. By binding with CTAB, the polyelectrolyte chain became more coiled as known from the reduced viscosity. The intramolecular NRET was dominant when [CTAB]Д᎒^-5 M and then the intermolecular NRET occurred at higher CTAB concentrations with hydrophobic aggregation between CTAB tails bound on different polyelectrolyte chains. The CTAB concentration corresponding to the maxima of I_Py/I_Np just is equal to the AMPS monomer concentration, indicating the formation of 1:1 binding between surfactant and polyelectrolyte in very dilute solutions. Added salt of NaCl up to 0.1 M hardly affected the intramolecular NRET but affected the I_Py/I_Np value for the intermolecular NRET.     

Aggregational behavior of N-butyloxycarbonyl-L-glutamic acid oligomeric benzyl esters (exact residue numbers 4, 6 and 8) in benzene. SAXS studies

N-Butyloxycarbonyl(BOC)-L-glutamic acid oligomeric benzyl esters with exact residue numbers (BOCN_pZ, N_p=4, 6 and 8) have been synthesized by a stepwise procedure in a liquid phase. The SAXS intensity spectra of the BOCN_pZ-benzene systems have been analyzed on the basis of the rod-like aggregate model, in which the #-sheet monomers are one-dimensionally stacked antiparallel to each other. The extracted parameters (the number-averaged aggregation number, the monomer-monomer bond energies corresponding to hydrogen bonding energies, and the number-averaged molecular weights) for these aggregates have been compared with those for the aggregates formed by N-acetyl-L-glutamic acid oligomeric benzyl esters (AN_pZ, N_p=4, 6 and 8) in benzene (PCCP, 2001, 3, 3140-3149). The results indicate that it is more difficult to form aggregates in the BOCN_pZ systems than in the AN_pZ systems. This difference is due to the bulky BOC group, which hinders the formation of aggregates.     

Strong electric-field effects on the doubly-excited intrashell states of He below the He+(N = 2) threshold

The method of complex-coordinate rotation is used to investigate electric-field effects on the doubly-excited 2s2p ¹P⁰, 2p^{2 1}D^e, 2p^{2 3}P^e and 2s2p ³P⁰ states of He. Strong electric-field strengths up to F=0.02 Ry are used in our present study. Products of Slater orbitals are used to represent the two-electron wave functions, with l_max=8 being employed for the individual electron. Block matrices with up to L_max=5 (H-states) are used to investigate the convergence behavior for the resonance parameters (resonance energy and width). When the external electric field is turned on, "classic" Stark effect is observed for the M=0 and M=ǃ components of the two singlet-spin states and for the M=ǃ components of the triplet-spin states. Comparisons are made with other calculations when available.     

The effect of poly(N,N-dimethylacrylamide) on the lamellar phase of Aerosol OT/water

The effect of a water-soluble uncharged polymer on the stability of the lamellar phase of the Aerosol OT (AOT)/water system is studied. The lamellar phase still exists when water is replaced by an aqueous solution of poly(N,N- dimethylacrylamide) (R_gƼ᎒² Å). Since the coil dimensions are (much) larger than the thickness of the water layers (d_wᅣ Å), the polymer molecules do not enter the lamellar phase. Instead segregation in small domains occurs, and in equilibrium with the AOT-rich phase another separate phase containing the polymer is formed. The polymer-rich phase exerts an osmotic pressure that reduces the water content in the AOT-rich phase, and by compression the repeat distance is reduced.     

Fourier transform IR spectroscopic study on phase transitions of copolymers of <Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide and alkyl acrylates in water

Copolymers of N-isopropylacrylamide (IPA) and alkyl acrylates [methyl acrylate (MA), ethyl acrylate, and butyl acrylate] or vinyl acetate have been prepared and their phase transitions in water have been observed by means of IR spectroscopy. The incorporation of these alkyl acrylates into a poly(IPA) (PIPA) chain induces a decrease in the phase-transition temperatures, T_p, and the magnitude increases with increasing size of the alkyl chains. The profiles of the C=O stretching absorption bands of the ester groups [9(C=O)_ester] and the IR bands due to IPA units exhibit critical changes at the T_p of these copolymers. The 9(C=O)_ester bands shift slightly toward higher wavenumbers (blueshift) upon phase transition, while the amide I and amide II bands of the IPA units undergo a blueshift and a redshift, respectively. Analysis of the 9(C=O)_ester band of PIPA-MA by using a curve-fitting method shows that it consists of three components, at 1,703, 1,720, and 1,738 cm^-1. The relative peak area of the largest component (1,720 cm^-1) is almost constant, and those of the 1,703-cm^-1 and 1,738-cm^-1 components increase and decrease with increasing temperature during the phase transition, respectively. However, the changes are rather small, suggesting that changes in hydrogen bonding of the C=O groups of MA units upon phase transition are not significant. The 9(C=O)_ester bands of other comonomers examined here also exhibit similar changes. The situation is consistent with the change in the hydration states of the amide groups of IPA units, most of which associate with water molecules through hydrogen bonds even after the phase separation.     

环烷酸类载体液膜体系对金属离子传输机理的研究

本文先在大块液膜体系中以环已烷甲酸为载体,通过正交设计,系统地研究了各种因素对希土离子输送作用的影响规律。比较了相同条件下RE~(3+)(希土)同Na~+,NH_4~+、Ca~(2+)和Fe~(3+)等离子的输送作用。发现在适当条件下,无皂化的羧酸载体对RE~(3+)离子具有良好的输送效果,同时证实,羧酸输送RE~(3+)离子是通过三个H~+离子与一个RE~(3+)离子的交换,而当载体皂化时,皂化的载体直接与接收相H~+离子发生交换,从而降低了羧酸对RE~(3+)离子的输送和分离效果。 在大块液膜研究的基础上,建立了一个以无皂化的环烷酸为载体的乳状液膜体系,从模拟离子矿的硫酸铵浸出液中萃取希土,通过正交试验确定了最优的液膜萃取条件,希土萃取率达96％以上,富集度30～40倍。     

线性变位极谱法研究 ⅩⅥ.铀(Ⅵ)-5-Br-PADAP-磺基水杨酸的配位吸附波

本文提出了铀(Ⅵ)-5-Br-PADAP-磺基水杨酸三元配合物的极谱配位吸附波。在pH为7.5-8.2的醋酸、三乙醇胺、乙醇底液中,该波的峰电位在-0.6855V(vs.SCE)。在1.00×10^-7-1.00×10^-5mol·dm^-3范围内,铀(Ⅵ)浓度与峰电流呈线性关系。对极谱波的电流、电位性质进行了研究,测定了配合物的组成、表观稳定常数和离解及生成速率常数。     

Cationic ring-opening polymerization of tetrahydrofuran with Keggin-type heteropolycompounds as solid acid catalysts

<正>Three Keggin-type heteropolyanions,namely H_3PMo_(12)O_(40)·13H_2O,(NH_4)_3PMo_(12)O_(40)·4H_2O and H_3PW_(12)O_(40)·13H_2O were prepared and tested in the ring-opening polymerization reaction of tetrahydrofuran.The effects of the counter-cation (H~+,NH_4~+) and the peripheral atoms(Mo,W) on the polymerization were investigated.It has been found that when the protons of H_3PMo_(12)O_(40)·13H_2O were replaced by the ammonium cations the polymerization rate decreased dramatically. Whereas,when the peripheral atoms(Mo) were replaced by their homologous(W),the polymerization rate increased twofold.As for the viscosity average molecular weight(M_v) of polymer products,it was found that the high molecular weight(7930) was obtained by using H_3PW_(12)O_(40)·13H_2O.The molecular weight(M_v) obtained by H_3PMo_(12)O_(40)·13H_2O and (NH_4)_3PMo_(12)O_(40)·4H_2O was 6470 and 6810,respectively.     

The counterion releasing effect and the partition coefficient of branched alkanols in ionic micellar solution

In the micellar solution of SDS, the partition coefficient (K_x) of following branched alkanols at infinite dilution was determined by applying a differential conductivity method: the alkanols used were i-C_mH_2m+1OH (m=4-9, i=1-5) in which the position of OH group (i) shifts from an end to the center of a hydrocarbon chain. The method provides two significant quantities, d!/dX_am and dC_sf/dC_af in addition to K_x. The following results have been obtained. (1) The dependence of K_x on i indicates that the hydrophobicity of alkanol is weakened with increasing i, whereas the increase in m strengthens the hydrophobicity. (2) The degree of counterion disossiation of micelles (!) is accelerated by the solubilized alkanols in micelles (mole fraction: X_am) and the acceleration rate, d!/dX_am (=0.17), depends on neither m nor i. (3) In the bulk water, the monomerically dissolved alkanols (concentration: C_af) depresses the concentration of free monomer surfactant (C_sf), and the depressing rate, dC_sf/dC_af, in micellar solution is identical with the corresponding quantity, ((CMC/(C_a)_o at CMC.     

Critical composition of ionic–nonionic mixed micelles for counterion condensation

In the mixed micelles of an ionic surfactant (sodium dodecyl sulfate) with a nonionic surfactant (N-decanoyl-N-methylglucamide, hexaoxyethylene glycol-mono-n-decylether, and hexaoxyethylene glycol-mono-n-dodecylether), the critical mole fraction, X_ic, of the ionic surfactant has been determined, below which the counterion is completely released from the micelles. The values of X_ic are 0.074, 0.11, and 0.11, for the respective nonionic surfactants. The valences, i.e., the aggregation numbers of the ionic surfactant, of the mixed micelles at X_ic are almost close to each other, around 6. At X_ic, the critical surface charge density (about 0.03 Cm^-2) for counterion condensation was tentatively calculated. In the present study, a differential conductivity method was applied.     

大比表面积钛黑颜料的制备和表征

本文首次通过pH值控制沉淀法制备前驱物丁二酸钛肼复盐,并进一步热分解制备大比表面积钛黑颜料-黑色钛氧化物。通过比表面积(BET)、电子能谱(EDS)、X射线光电子能谱分析(XPS)、X射线粉末衍射(XRD)、场发射扫描电子显微镜(HRSEM)、物理吸附仪、激光粒度仪和Color i5型台式分光测色仪对黑色钛氧化物进行了表征,确定了黑色钛氧化物的组成为2TiO2·Ti2O3,其表面积为53.854 4 m2·g-1。并考察了酸源、水合肼用量、酸钛比、反应时间、pH、NaOH浓度和煅烧温度等各种反应参数对黑色钛氧化物的颗粒尺寸、分布均匀性和黑色度的影响。用元素分析仪和等离子体光谱仪测定了前驱物组成,确定其组成为[Ti(C4H4O4)2]0.85·2Ti2O3·6N2H4·3H2O,并探讨了黑色钛氧化物形成机理,为新型混合价材料黑色钛氧化物的制备提供重要参考依据。     

含磷钼酸及2,2’-联吡啶-3,3’-二羧酸配体的铜配位聚合物的合成、晶体结构与电化学性质

在水热条件下合成了一个新的化合物{[Cu4(PMo12O40)(H2O)5(H2bpdc)(Hbpdc)(bpdc)2].6H2O}n(H2bpdc=2,2′-联吡啶-3,3′-二羧酸),并用元素分析、IR、TG和X-射线衍射等手段进行了表征。结果表明本化合物的晶体结构中,最小不对称单元包含1个[Cu4(H2O)5(H2bpdc)(Hbpdc)(bpdc)2]3+阳离子,1个[PMo12O40]3-阴离子和6个结晶水分子。Cu(Ⅱ)与相邻[PMo12O40]3-的桥氧原子配位,形成一维链状结构。电化学研究表明,化合物存在三步氧化还原过程。     

12-钼磷酸的BrÖnsted酸位和Lewis酸位

研究了加热、抽空等预处理对固态12-钼磷酸(PMA)酸位的影响。发现了PMA上除存在B-酸位外,还可生成L-酸位。研究了PMA上L-酸位的成因,水在两类酸位形成过程中的作用,L-酸位与B-酸位的相对强度,以及PMA上酸强度的分布。据此,对Miscno等认为PMA中只存在质子酸和酸强度分布均匀的观点提出了不同的看法。     

DEVELOPMENT OF A CATALYST FOR SOLUTION OF POLY(VINYL ALCOHOL) IN NON-AQUEOUS MEDIUM

Chloro ethane dimethyl sulfoxide,C_2H_5Cl·DMSO(ECI·DMSO)was prepared by interaction of acrylic acid with conc.Hydrochloric acid in dimethyl sulfoxide(DMSO)and subsequent decarboxylation with H_2O_2 solution.The formation of the compound was confirmed by spectral and analytical methods;the molecular weight was determined by cryoscopic method.The solubility of poly(vinyl alcohol)(PVA)in different solvents or mixed solvents at 40℃,50℃and 60℃temperature in the presence of 0.01% of EC1·-DMSO was determined.It...     

Interactions between synthetic and indigenous naphthenic acids and divalent cations across oil–water interfaces: effects of addition of oil-soluble non-ionic surfactants

Interactions between naphthenic acids and divalent metal cations across model oil–alkaline water interfaces were investigated by correlating changes in dynamic interfacial tension (IFT), to plausible reaction mechanisms. The measurements were carried out by using a CAM 200 optical instrument, which is based on the pendant drop technique. The naphthenic acids used were synthesised model compounds as well as commercial acid mixtures from crude distillation and extracted acid fractions from a North Sea crude oil. The divalent cations involved Ca²⁺, Mg²⁺, Sr²⁺, and Ba²⁺, which are all common in co-produced formation water and naphthenate deposits. The results show that the dynamic IFT strongly depends on naphthenic acid structure, type of divalent cation, and the concentration of the compounds as well as the pH of the aqueous phase. Introducing divalent cations to systems involving saturated naphthenic acids caused mostly a permanent lowering of the IFT. The decline in IFT is due to electrostatic attraction forces across the interface between the cations in the aqueous phase and the carboxylic-groups at the o/w interface, which cause a higher interfacial density of naphthenic acid monomers. The permanent lowering in IFT is likely due to formation of positively charged monoacid complexes, which possess high interfacial activity. On the other hand, in the case of the aromatic model compounds, the cations affected the IFT differently. This is mainly discussed in light of degree of cation hydration and steric conditions. Various oil-soluble non-ionic surfactant mixtures were also introduced to systems involving a model naphthenic acid and Ca²⁺ in order to investigate how the interfacial competition affected the local interactions. Based on the behaviour of dynamic IFT, probable inhibition mechanisms are discussed.Electronic Supplementary Material Supplementary material is available for this article at     

Isolation and Characterization of Naphthenic Acids from a Metal Naphthenate Deposit: Molecular Properties at Oil‐Water and Air‐Water Interfaces

Naphthenic acids from a West African metal naphthenate deposit have been isolated and characterized by infrared (IR), nuclear magnetic resonance (NMR), and Fourier transform ion cyclotron resonance mass spectrometry (FT‐ICR MS). The sample has been shown to comprise a narrow group of 4‐protic naphthenic acids of molecular weight ～1230 Da. The determined mass of 1230.0627 Da suggests a compound with the elemental composition C₈₀H₁₄₂O₈. The NMR data show no sign of carbon‐carbon multiple bonds. Hence, the elemental composition indicates the presence of six saturated hydrocarbon rings. The naphthenic acids have proved to be highly oil‐water (o/w) interfacially active. On elevation of the pH from 5.6 to 9.0, interfacial activity increases gradually due to a higher degree of dissociation of the carboxylic groups. At pH 9.0, the interfacial tension (IFT) between water and toluene‐hexadecane (1–9 vol.) is lowered by ～40 mN/m at concentrations of only 0.0050–0.010 mM naphthenic acid. The time rate of decrease of the IFT (dγ/dt) is also concentration‐dependent, and a well‐defined IFT is attained at long observation periods.

The C₈₀ naphthenic acids form relatively unstable Langmuir monolayers. The stability decreases further with increasing pH as more monomers become dissociated and dissolve into the aqueous phase. The stability is altered upon addition of calcium ions into the subphase due to formation of calcium naphthenate at the surface. In the undissociated state, the acids have a molecular area of ～160 Å²/molecule in the noninteracting region. The high area reflects an extended molecular structure comprising four carboxylic head groups, which are likely to be separated by hydrocarbon chains.