Microemulsion polymerization of acrylamide and styrene: Effect of the structures of reaction media

Isothermal phase diagrams of the system cetyltrimethylammonium bromide (CTAB)/n‐butanol/n‐octane/water were constructed, and the effect of the oil (n‐octane) contents on the microemulsions was studied at 40 °C. We determined the microemulsion structures of two systems, CTAB/n‐butanol/10% n‐octane/water and sodium dodecyl sulfonate (As)/n‐butanol/20% styrene/water, by conductivity measurements to investigate the polymerization of acrylamide and styrene in the two microemulsion systems. The polymerization kinetics of the water‐soluble monomer acrylamide in CTAB micelles and the different CTAB/n‐butanol/10% n‐octane/water microemulsion media [water‐in‐oil (W/O), bicontinuous (BC), and oil‐in‐water (O/W)] were studied with water‐soluble sodium bisulfite as the initiator. The maximum polymerization rate in CTAB micelles was found at the second critical micelle concentration. A mechanism of polyacrylamide formation and growth was proposed. A connection between the structures of the microemulsions and the polymerization rates was observed; the maximum polymerization rate occurred at two transition points, from W/O to BC and from BC to O/W, and the polyacrylamide molecular weights, which depended on the structures of the microemulsions, were also found. A square‐root dependence of the polymerization rates on the initiator concentrations was obtained in CTAB micelles and O/W microemulsion media. The polymerization of the oil‐soluble monomer styrene in different As/n‐butanol/20% styrene/water microemulsion media (W/O, BC, and O/W) was also investigated with different initiators: water‐soluble potassium persulfate and oil‐soluble azobisisobutyronitrile. A similar connection between the structures of the microemulsions and the conversions of styrene in CTAB/n‐butanol/10% n‐octane/water for the polymerization of acrylamide was observed again. The structures of the microemulsions had an important role in the molecular weights and sizes of polystyrene. The polystyrene particles were 10–20 nm in diameter in BC microemulsion media and 30–60 nm in diameter in O/W microemulsion media according to transmission electron microscopy. We determined the solubilization site of styrene in O/W microemulsion drops by ¹H NMR spectra to analyze the results of the microemulsion polymerization of styrene. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3320–3334, 2001     

Microemulsion copolymerization of styrene and acrylonitrile with n‐butanol as the cosurfactant

The microemulsion copolymerization of styrene and acrylonitrile in an n‐butanol/cetyltrimethylammonium bromide/oil/water microemulsion system was studied. The solubilization sites of the two monomers were determined with an NMR technique. The results showed that the solubilization behaviors of the two monomers were quite different. Most of the styrene was solubilized in the palisade layer of the microemulsion, whereas the acrylonitrile had an equilibrium distribution in the aqueous phase and palisade layer of the microemulsion. The reactivity ratios of styrene and acrylonitrile in the microemulsion system were different from those in other media. The effect of the monomer feed composition on the copolymerization kinetics was investigated, and the mechanism of nucleation of the latex particles was examined. The experimental results showed that the copolymerization loci were changed from the microemulsion droplets to the aqueous phase when the concentration of acrylonitrile in the monomer feed reached approximately 80%; this could be further proved by the effect of the monomer feed composition on the copolymerization kinetics. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 203–216, 2005     

Hydrolytic Cleavage of Paraoxon by Octanohydroxamate Ion in Cationic Microemulsions

The hydrolysis reaction of O,O‐diethyl O‐p‐nitrophenylphosphate (Paraoxon) with the octanohydroxamate ion (OHA^?) was studied in a cationic oil‐in‐water (O/W) microemulsion system over a pH range 7.5–12.0 at 300 K. The O/W systems are stabilized by using cationic surfactant, cetyltrimethylammonium bromide (CTAB), and n‐butanol as cosurfactants. In a microemulsion, the rate enhancement by OHA^? is greater toward the cleavage of paraoxon than its spontaneous (2.1 × 10⁷ s^?1) hydrolysis. The k_obs values for the reaction of paraoxon with OHA^? were determined in different microemulsion compositions with varying chain length of alcohols (n‐butanol, n‐pentanol, n‐octanol, and n‐dodecanol) and alkanes (n‐hexane, n‐heptane, and n‐decane). The effects of water content, pH, and size of the oil pool have been discussed.     

The Inhibition of the Hydrolysis of Cephanone by CTAB/n‐C5H11OH/H2O Microemulsion

Abstract

The hydrolysis of cephanone in water, cetyl trimethyl ammonium bromide (CTAB) micelle, and CTAB/n‐C₅H₁₁OH/H₂O O/W microemulsion was studied through UV‐VIS absorption spectroscopy. The mechanism of the hydrolysis and the effects of both the acidity of the media and the composition of O/W microemulsion on the hydrolysis were studied. The results show that the hydrolysis rate of cephanone increases with the acidity. Compared with water, CTAB micelle and CTAB/n‐C₅H₁₁OH/H₂O O/W microemulsion suppress this hydrolysis. The inhibition of the hydrolysis of cephanone by CTAB micelle and CTAB/n‐C₅H₁₁OH/H₂O O/W microemulsion is related to the location of cephanone in the interphases of CTAB micelles and CTAB/n‐C₅H₁₁OH/H₂O O/W microemulsion droplets.     

Formation of ionic liquid submicron particles. 1H and 19F nuclear magnetic resonance spectroscopic studies

We prepared novel ionic liquid submicron particles (ILSPs) in water by emulsifying the ionic liquid (IL) N-(2-methoxyethyl)-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr_12O1TFSI), which is immiscible with water, with the nonionic surfactants Tween 20 and Span 80. The mean particle size and zeta potential of the ILSPs were about 580?nm and ?30?mV, respectively. The ILSPs were characterized using ¹H and ¹⁹F nuclear magnetic resonance (NMR) spectroscopic methods. The chemical shifts of the Pyr_12O1⁺ cation and TFSI^? anion in the ¹H and ¹⁹F NMR spectra of the ILSP suspension were consistent with those corresponding to pure Pyr_12O1TFSI. This indicated that most of the Pyr_12O1TFSI was still in the IL state in the ILSP suspension. In addition, ¹H–¹H nuclear Overhauser effect correlated spectroscopic measurements showed that the ILSP droplets contained Pyr_12O1TFSI in the neat IL steric state even in the ILSP suspension, and Pyr_12O1TFSI species localized in the droplet surfaces interacted with the hydrophobic acyl side chains of the surfactants. These NMR spectroscopic results show that the ILSPs formed an IL-in-water microemulsion in which droplets of neat Pyr_12O1TFSI were surrounded by the two surfactants, that is, Tween 20 and Span 80.     

Hydrotrope and hydrotrope-solubilization action of cephanone in CTAB/<Emphasis Type="Italic">n</Emphasis>-C<Subscript>5</Subscript>H<Subscript>11</Subscript>OH/H<Subscript>2</Subscript>O system

Cephanone is found to show the hydrotrope and hydrotrope-solubilization action in CTAB/n-C₅H₁₁OH/H₂O system. Cephanone can increase the solubilities of cationic surfactant CTAB or n-C₅H₁₁OH in water and water in n-C₅H₁₁OH. It can also increase the solubilization amount of n-C₅H₁₁OH in O/W microemulsion and that of water in W/O microemulsion, which makes the two regions of O/W and W/O microemulsion larger, and even linked together. The mechanism of the hydrotrope-solubilization action of cephanone is related to the location of cephanone in the palisade of microemulsion which causes the stability of O/W and W/O microemulsion to be enhanced and that of lamellar liquid crystal to be reduced. Therefore, the mechanism of hydrotrope-solubilization is the structural transition from lamellar liquid crystal to the bicontinuous structure.     

Hydrotrope‐Solubilization Action of Urea in CTAB/n‐C5H11‐OH/H2O System

Urea can enhance the aqueous solubility of surfactant CTAB (hexadecyltrimethylammonium bromide) when it shows the hydrotrope action. It will show the hydrotrope‐solubilization action when the solubilized amount of n‐C₅H₁₁OH in O/W microemulsion and that of water in W/O microemulsion are increased. The mechanism of the hydrotrope‐solubilization action of urea is the increase of the stability of W/O and O/W microemulsion and structural transition from the lamellar liquid crystalline phase to the bicontinuous structure.     

Dependence on Oil Chain‐Length of the Curvature Elastic Properties of Nonionic Surfactant Films: Droplet Growth from Spheres to a Bicontinuous Network

Using NMR self‐diffusion and ²H‐NMR relaxation experiments, we have investigated growth of oil‐in‐water microemulsion droplets when spontaneous curvature is lowered, starting at emulsification failure boundary. We compare two ternary nonionic microemulsion systems, containing penta‐ethylene glycol dodecyl ether (C₁₂E₅), and decane or hexadecane, at same surfactant‐to‐oil ratio and approximately the same spontaneous curvature. Droplet growth in microemulsions appears in general to be only minor. Quantitative differences between the two systems indicate differences in the curvature elastic constants.     

Studies on the Middle-phase Microemulsion of Lauric-N-methylglucamide

The phase behaviour of the middle-phase microemulsion for the quaternary system lauric-N-methylglucamide （MEGA-12）/n-butanollalkane/water has been studied with Winsor type, δ-γ, fishlike and novel ε-β fishlike phase diagrams. A series of phase inversions Winsor I （2）→Ⅲ（3）→Ⅱ （ 2 ） were observed for the three kinds of phase diagrams. The phase types, the phase volumes and the range of alcohol concentrations from the beginning to the end of the middle-phase microemulsion were obtained from Winsor phase diagram. From δ-γ, fishlike phase diagram, the physicochemical parameters, such as the mass fraction of n-butanol in the hydrophile-lipophile balanced inteffacial layer, A^s, the coordinates of the start and end points of the middle-phase microemulsion, and the solubilities of MEGA-12 and n-butanol in alkane phase were calculated. The novel ε-β fishlike phase diagram was also presented. From this kind of diagram, the above experimental phenomena were observed and the physicochemical parameters were calculated precisely. The novel fishlike phase diagram has advantages over the Winsor and δ-γ fishlike phase diagrams in the evaluation of the solubilization power of the microemulsion and calculation of the related physicochemical parameters.     

烷基聚葡糖苷C9.6G1.3/n-C4H9OH/n-C6H14/H2O微乳液体系的介电弛豫谱研究

The pseudotertiary phase diagram of the microemulsion system alkyl polyglucoside/n-butanol/n-hexane/water was plotted at （30.0±0.1） ℃. The dielectric measurements, including permittivity, conductivity, relaxation strength, characteristic relaxation time, etc,, were applied to investigate the microstructure of the system. Unique dielectric relaxations were observed over the frequency range of 5-10^7 Hz, taking place possibly through an interracial polarization mechanism. According to the results obtained from dielectric spectroscopy, the structures of the microemulsion O/W, BC and W/O were determined, and some dielectric and phase parameters were calculated.     

Kinetic Study of Radical Polymerization VI. Copolymer Composition and Kinetic Parameters for Coplymerization of Styrene‐Itaconic Acid by On‐Line 1H‐NMR

Free radical solution copolymerization of styrene (St) and itaconic acid (IA) in dimethylsulfoxide‐d₆ (DMSO‐d₆) as the solvent and the use of 2,2′‐azobisisobutyronitrile (AIBN) as the initiator at 78°C was investigated by an on‐line ¹H‐NMR spectroscopy technique. Individual monomer conversion vs. reaction time, which was calculated from the ¹H‐NMR spectra data, was used to study the drift in monomer mixture composition vs. conversion. It was found that in general, both monomers were incorporated almost equally into the copolymer. However, when the mole fraction of IA was low, the tendency of IA toward incorporation into the copolymer chain was somewhat higher than St and by increasing the mole fraction of IA in the reaction mixture, the inverse tendency was observed. Overall monomer conversion as a function of time was calculated from individual monomer conversion data and used for the estimation of k_p /k_t ^0.5 for various monomer mixture compositions. This ratio was decreased with increasing the amount of IA in the initial feed, indicating a decrease in the rate of copolymerization. Changes in the copolymer composition vs. overall monomer conversion were investigated experimentally from the NMR spectra. This was in good agreement with the changes in monomer mixture composition vs. reaction progress. Plotting the copolymer composition vs. initial monomer feed showed tendency of the system toward alternating copolymerization.     

Preparation and in vitro Release Test of Insulin Loaded W/O Microemulsion

A W/O microemulsion of Tween‐80‐Span‐80/n‐butylalcohol/ethyl‐oleate/H₂O to envelop insulin (INS) was prepared. In order to obtain the maximum solved water, the components of microemulsion to envelop INS were chosen with the pseudo‐ternary phase diagram and the influences of temperature, salinity as well as the pH on microemulsion areas also were investigated. To test the properties of the microemulsion, the conductance was used to divide O/W, W/O and BC regions, the dynamic light scattering to evaluate the particle diameters of microemulsion, the ¹²⁵I isotope tracing method to measure the release rate of INS loaded in W/O microemulsion, and the growth inhibitory effect test to appraise the cytotoxicity on human normal cells. Results show that W/O microemulsion forms when water content below 50% in the microemulsion system. The microemulsion region decreases slightly with the increase of temperature, salinity and the decrease of pH. However, the viscosity measurements along certainly selected dilution lines to the microemulsion indicate that no phase invert occurred. Diameter of microemulsion particle increases with the addition of INS, and the increase is sharp in the first 5 days then very slightly at 68.6 nm within a month. The INS loaded W/O microemulsion possesses eminent sustaining release efficiency and the cytostatic as well as cytotoxic assays illustrate that the microemulsion can be used as drug delivery at small dosage.     

NMR studies of molecular motion in tetramethylammonium hydroxide pentahydrate

Polycrystalline (CH₃)₄NOH·5 H₂O (I) and (CH₃)₄NOD·5D₂O (II) have been studied by¹H NMR lineshapes, second moments and spin-lattice relaxation times and by²H NMR lineshapes as a function of temperature. From low temperatures the first motion to occur is reorientation of the internally rigid (CH₃)₄N⁺ ion about a uniqueC ₃ axis (E _ta = 8.37 kJ/mol forI,E _a = 9.00 kJ/mole forII), followed closely by pseudo isotropic reorientation of the whole ion (E _a = 18.10 kJ/mol). Motion of the cage molecules (water and hydroxide ion) occurs at higher temperatures with an apparentE _a = 11.30 kJ/mol. There is some evidence of a phase transition inII but notI in the 220–230 K region.²H NMR lineshapes ofII below 220 K indicate static cage molecules. Some of the²H quadrupole coupling constants derived from these spectra correspond to O·O hydrogen-bond distances which are incompatible with the known room temperature structure ofI. Above the possible transition inII the anisotropic²H lineshapes indicate rapid motion of²H among all possible hydrogen-bond sites via transfer along the bonds and molecular reorientation. This motion persists in the high temperature phase but the lineshape becomes isotropic due to the cubic symmetry of this phase. It is possible that¹H or²H tunnelling plays an important part in the motion of the cage molecules and the different phase behaviour ofI andII.Dedicated to Dr D. W. Davidson in honor of his great contributions to the sciences of inclusion phenomena.     

微乳液中苯乙烯聚合反应的研究

测定了十二烷基磺酸钠(As)/正丁醇/20%苯乙烯/水体系相平衡。用油溶性偶氮二异丁腈(AIBN)和水溶性过二硫酸钾(K~2S~2O~8)为引发剂,研究了油包水(W/O)、双连续(BC)和水包油(O/W)型微乳液介质中苯乙烯的聚合反应。得到了苯乙烯转化率和聚苯乙烯分子量与体系水含量之间的关系,讨论了微乳液结构对聚合作用的影响。并通过电镜观察了聚苯乙烯的形貌,求得了聚苯乙烯的粒径,同时用^1HNMR研究了苯乙烯在微乳液液滴中的增溶位置,分析了聚合作用的实验结果。     

Synthesis, characterization and solution behaviour of phosphoryl complexes of tin tetrafluoride

The preparation and characterization of a series of octahedral complexes [SnF₄L₂] (L = (Me₂N)₃PO (1), L = (R₂N)₂P(O)F; R = Me (2); Et (3) or L = R₂NP(O)F₂; R = Me (4); Et (5)) are described. These new adducts have been characterised by multinuclear (¹⁹F, ³¹P and ¹¹⁹Sn) NMR, IR spectroscopy and elemental analysis. The NMR data particularly the ¹⁹F NMR spectra showed that the complexes exist in solution as mixtures of cis and trans isomers. The solution behaviour of the complexes studied by variable temperature NMR in the presence of excess ligand indicated that, unlike in the SnCl₄ analogues, the ligand exchange at room temperature is slow for 1–3 and fast only for 4 and 5. The metal–ligand exchange barriers in [SnF₄L₂] and [SnCl₄L₂] systems were estimated and compared. The results indicate that in addition to the difference in the Lewis acidity between SnF₄ and SnCl₄ the nature of the substituents (fluorine atoms) on the phosphorus atom of the ligand can contribute considerably to the lability of the complex obtained.     

Phase Behavior of n‐Butanol/n‐Octane/Water/Cationic Gemini Surfactant System

Phase diagrams of the n‐butanol/n‐octane/water/(12‐3‐12,2Br^?1) system were determined, where n‐octane usually represents oil (O), 12‐3‐12,2Br^?1 is a gemini cationic surfactant trimethylene‐1,3‐bis(dodecyldimethyl ammonium bromide) abbreviated as S, and n‐butanol is a co‐surfactant written as A. Effects of the weight ratio of gemini surfactant to cosurfactant, S/A, and of temperature on the phase behavior were studied. The microemulsion structures including O/W, bi‐continuous (B.C.), W/O, and liquid crystal were determined by the conductivity method and polarization measurement. Experimental results show that the gemini surfactant, used facilitates the formation of microemulsions compared with its corresponding monomeric surfactant, n‐dodecyl trimethylammonium bromide (DTAB). When S/A=1/1, and the total concentration of gemini surfactant and alcohol is 20–40%, microemulsions with higher water content can form in a wider region. When the temperature increases, the size and position of each type of microemulsion region changes notably.     

Phase Behavior and Dielectric Spectroscopy of the Sodium Dodecyl Trioxyethylene Sulfate／n－Butanol／Water System

Introduction　　Itiswellknownthatsurfactantsinanaqueoussolu tioncouldformmicellesataconcentrationhigherthanthecriticalmicelleconcentration (cmc) .Knowledgeofalcoholsolubilizationinaqueousmicellesolutionsisimportantinunderstandingtheaggregationbehaviorofsuchsystemsandisrelevanttoseveralindustrialprocesses .1Manystudieshavebeenreportedonphasebehaviorofternarysystemsofionicsurfactant,alcohol,andwater.2 7Generally ,inthecaseofshortchainalcohol,atransparent,isotropic ,andlow viscosityphaseappearse…     

Cadmium(II) complexes with phosphine tellurides: synthesis and multinuclear (31P, 125Te,and 113Cd) NMR characterization in solution

New cadmium(II) complexes with phosphine telluride ligands of the type CdX₂(R₃PTe)_n [X?=?ClO₄^?, n?=?4: R?=?n-Bu (1), Me₂?N (2), C₅H₁₀?N (3), C₄H₈?N (4) or OC₄H₈?N (5); X?=?Cl^–, n?=?2: R?=?n-Bu (6), Me₂?N (7), C₅H₁₀?N (8), C₄H₈?N (9) or OC₄H₈?N (10)] have been synthesized and characterized by elemental analyses, IR and multinuclear (³¹P, ¹²⁵Te, and ¹¹³Cd) NMR spectroscopy. In particular, the solution structures of these complexes were confirmed by ¹¹³Cd NMR at low temperature, which displays a quintuplet for each of the perchlorate complexes and a triplet for each of the chloride complexes due to coupling with four and two equivalent phosphorus atoms, respectively, indicating a four-coordinate tetrahedral geometry for the metal center. These multiplet features were further accompanied by one bond Te–Cd couplings, clearly showing that the ligand is coordinated to the metal through tellurium. The results are discussed and compared with those obtained for closely related phosphine chalcogenide analogs.     

Deprotonated Amines Formed Through Coordination to Sulfur/Oxygen-Bridged Incomplete Cubane-Type Molybdenum Clusters

Oxygen/sulfur-bridged incomplete cubane-type molybdenum aqua clusters [Mo₃( ₃-S)(-X)(-S)₂(H₂O)₉]⁴⁺ (X=O, S) in hydrochloric acid react with dien (diethylenetriamine) to give [Mo₃( ₃-S)(-X)(-S)₂(dien^–)(dien)₂]Cl₃·nH₂O [1, X=O, n=3; 2, X=S, n=4; dien^–=NH₂(CH₂)₂NH(CH₂)₂NH^–], respectively, where each cluster has a deprotonated dien. The X-ray structural analysis of 1 revealed proton dissociation from an amino group of one of the three dien ligands: one Mo–N distance [1.987(4) Å] is clearly shorter than the other eight Mo–N distances [2.229(3)–2.276(3) Å]. The ¹H NMR spectra of the Mo–dien clusters 1 and 2 in D₂O show two well-resolved methylene proton signals in the 2.8- to 3.0-ppm region, which indicates that both deprotonated amines in 1 and 2 receive D⁺ ions from solvent D₂O. The factors for the proton dissociation are discussed.     

Effects of isomeric alcohols on the phase behavior and solubilization of the microemulsion systems formed by anionic surfactants

The middle-phase ɛ-β fishlike phase diagrams of the pseudoquaternary microemulsion systems sodium dodecyl sulfate (sodium dodecyl sulfonate, sodium dodecyl benzene sulfonate)/1-butanol (2-butanol, t-butanol)/n-octane/brine (5% NaCl) were plotted. The effect of three isomeric alcohols (1-butanol, 2-butanol, and t-butanol) on the phase behavior and solubilization was investigated. From the ɛ-β fishlike phase diagram, the composition of the interfacial layer, the solubilities of alcohols and the solubilization ability (the solubility parameter SP*, and the middle-phase volume fraction ϕ) of the microemulsion systems were calculated and discussed. The alcohol content in the interfacial layer and the solubilities of alcohols are in the order: 1-butanol < 2-butanol < t-butanol, but the solubilization ability is in the inverse order.