Micellisation and gelation of block-copoly(oxyethylene/oxybutylene/oxyethylene) E58 B17 E58

A triblock-copoly(oxybutylene/oxyethylene), denoted E₅₈ B₁₇ E₅₈ (80 wt-% E), was prepared by sequential anionic copolymerisation and its micellar and gelation properties in aqueous solution were determined. The oxybutylene/oxyethylene copolymer had the advantage over comparable oxypropylene/oxyethylene copolymers of greater uniformity of composition and chain length. The methods generally used were surface tension, light scattering intensity, photon correlation spectroscopy, together with observation of gelation. Measurements were made at 30°, 40° and 55° C over a full concentration range from dilute solution into the gel (>200 g dm^–3) and at specified concentrations, including the gel, over the temperature range from 10° to 70° C. The lower and upper temperature boundaries of the gel region were identified, and the occurrence of syneresis was noted. The properties investigated and discussed include critical micelle and gel concentrations, micellar weights and sizes, and structures and mobilities in the gel.     

用SAXS/WAXS研究聚氧乙烯/聚氧丁烯嵌段共聚物在n-己烷中的结晶性球形胶束结构

嵌段共聚物在选择性溶剂中能够自组装形成胶束,胶束的不同形状与嵌段共聚物的结构、溶剂和浓度有关．无定形嵌段共聚物通常形成球形胶束,在某些情况下也可以形成其它形状的胶束,关于结晶性嵌段共聚物在无定形链段选择性溶剂中的胶束结构和形状的报道非常少．由于结晶和相似相溶两种作用力的竞争,使得这类胶束的形状丰富多变．通常结晶作用较强时,结晶性嵌段共聚物形成片状的胶束,当结晶组分比较少时,可形成棒状胶束,尽管理论上已经指出存在球形胶束,但尚无关于这方面的报道。     

Raman spectroscopic study of temperature dependence of water structure in aqueous solutions of a poly(oxyethylene) surfactant

The temperature dependence of the water structure in aqueous solutions of a poly(oxyethylene) surfactant C₁₂E₅ was examined at concentrations 0, 20, 30, 45, 70 and 90 wt% by Raman spectroscopy of the O–H stretching band. The ratio of the intensities of the component around 3200 cm⁻¹ (the collective in-phase O–H stretching vibrations of bonded aggregates) to the component around 3400 cm⁻¹ (the O–H stretches in which the phase relations are lost) was monitored in the temperature range from 0 to 39 °C. The results show that the speed of the thermal destruction of the H-bond network increases as the concentration increases from 0 to 45 wt%. This change is attributed to the existence of a substantial amount of water in the system that takes part in the hydrophobic hydration of the poly(oxyethylene) headgroups, despite their predominantly hydrophilic character. The conclusion that this kind of water, which is known to have restricted mobility, plays an important role in the surfactant–water systems is consistent with the high viscosity of the liquid crystalline phases.     

PEG/(NH4)2SO4双水相体系萃取甘草中的有效成分

甘草的主要有效成份甘草酸具有消炎解毒、抗氧自由基、调节机体免疫力等作用,目前已被广泛应用于食品、饮料、化妆品、医药、卷烟等行业。工业上广泛应用的是水提法,该法操作容易、设备简单、溶剂价廉,但提取效率不高,易造成资源浪费。双水相萃取技术(Two-aqueous phase extraction,简称．ATPS),是近年出现的新型生物化工分离技术。由于双水相萃取分离过程条件温和、可调节因素多、易于放大和操作,不存在有机溶剂残留问题,特别适用于生物物质及天然资源中有效成分的分离和提纯。     

Amphiphilic Comb‐Like Poly(oxyethylene) and Its Complexes with LiClO4: Synthesis and Mesomorphic Behavior

Summary: We prepared an amphiphilic, comb‐like poly(oxyethylene) containing decyl‐tri(oxyethylene) amphiphiles in the side chain using a polymer analogous reaction to obtain a novel nonionic amphiphilic polymeric system with high molecular weight. The amphiphilic comb‐like poly(oxyethylene) itself only showed a side‐chain crystalline phase below its melting temperature of −31 °C. When the polymer was mixed with lithium perchlorate, a smectic liquid‐crystalline phase appeared. The ordered phases of the polymer and the polymer mixture were studied by differential scanning calorimetry, polarized optical microscopy, and X‐ray diffraction.

POM image (200 X) of D3OTP1 at room temperature.     

硫酸铯/聚乙二醇双水相体系在298.15K的相平衡

水溶性高聚物的双水相体系可用于纯化一些无机盐,获得高纯晶体。由于高聚物的存在会减小盐在溶液中的溶解度,从而可能析出晶体。本文采用自制的相平衡装置,测定了硫酸铯／聚乙二醇(PEG1000,4000,10000)双水相体系在298．15K时的等温平衡溶解度。     

Star-graft copolymers. Synthesis of amphiphilic graft copolymers with star-branched poly(oxyethylene) side chains

The synthesis of novel amphiphilic star-graft (SG) copolymers containing hydrophilic poly(oxyethylene) (PEO) side chains attached to a hydrophobic backbone by multifunctional entity is reported. In a first step poly(phthalimidoacrylate-co-styrene) was converted into polymers containing different number of multifunctional branching cites distributed along the main chain by partial aminolysis of the phthalimidoacrylate units with tris(hydroxymethyl)aminomethane. In the second step, these reactive copolymers yielded SG copolymers with different number of star-shaped PEO side groups by reaction with isocyanato terminated methoxy–PEO. The copolymers were characterized by size-exclusion chromatography, IR-, and NMR-spectroscopy. Their thermal properties were examined by thermal gravimetric analysis and differential scanning calorimetry. The studies indicate that the grafting degree and hydrogen bonding determine to a great extent the behavior of the SG copolymers in solid state and in solution. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 673–679, 1997     

A rheological investigation of aqueous solutions of poly (vinyl alcohol) during aging. Part IV: Repeated aging of concentrated solutions

Aging of aqueous solutions of poly (vinyl alcohol) obtained by melting of gels, formed in the aging process from solutions prepared by the dissolution of the polymer in hot water, was investigated using non-Newtonian viscometry and normal stress measurement. It was shown that, if the gels undergo melting at the same temperature at which the original solutions were prepared, aging of such solutions proceeds in the same way as in the case of the original solutions. If melting occurred due to heating at lower temperature, the resulting solutions aged more quickly.     

Cd(II) determination in the presence of aqueous micellar solutions

The equilibrium constants and molar absorptivities for the fast formation of a 1:3 complex between cadmium(II) (Cd(II)) and dithizonate anion, in the presence of cationic and non-ionic surfactants, allowed a simple and fast spectrophotometric determination of total cadmium. Indeed, the molar absorptivities of the Cd(II)-dithizone (Dz) complex formed in the presence of the neutral Triton X-100 and cationic cetyltrimethylammonium bromide (CTAB) surfactants are almost twice the value observed in the standard method and the maxima of absorption are shifted by about 40 nm when compared with the standard method. Clearly, the use of neutral and cationic surfactants promotes a higher value of the molar absorptivities of the complex, resulting in an increase in the sensitivity of the method. Application of the method to the desorption of Cd(II) ions from clays is illustrated.     

Solution properties of an aqueous poly(methacryl oxyethyl trimethylammonium chloride) and its poly(oxyethylene) grafted analog

Cationic poly(methacryl oxyethyl trimethylammonium chloride), PMOTAC, and its poly(oxyethylene), POE, grafted analog have been synthesised. The molar mass of the POE grafts was M_w = 200 g/mol, and the grafting degrees of the synthesised copolymers were 2, 5, and 15 mol %. The effect of the POE grafts on the solution properties and the conformation of the polycation has been investigated in aqueous NaNO₃ by means of dynamic and static light scattering, viscometry, and Raman spectroscopy. It was found that the polyelectrolyte properties are more pronounced for the homopolymer than for the POE‐grafted copolymers. The increase of the POE‐grafting degree dramatically decreases the hydrodynamic radius of individual macromolecules and causes intermolecular association. It also suppresses the conformational response of the copolymers upon changing the ionic strength with respect to that of the homopolymer. DFT calculations have been used to estimate a possible mechanism of interaction between the POE grafts and the MOTAC repeating units. It has been revealed that the POE grafts are capable of forming intramolecular hydrogen bonds with the MOTAC groups. The latter was confirmed experimentally; addition of free POE chains to a solution of PMOTAC results in formation of intermolecular PMOTAC/POE complexes. Increasing the POE concentration decreases the solution viscosity. At the same time, the bimodal distributions of the hydrodynamic radius, which are typical for polyelectrolytes in salt‐free solutions, become monomodal representing the PMOTAC/POE complexes. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 547–557, 2008     

Darstellung,Ramanspektren und Kristallstrukturen von V2O3(SO4)2, K[VO(SO4)2] und NH4[VO(SO4)2]

Preparation, Raman Spectra, and Crystal Structures of V₂O₃(SO₄)₂, K[VO(SO₄)₂], and NH₄[VO(SO₄)₂] The oxo-sulfato-vanadates(V) V₂O₃(SO₄)₂, K[VO(SO₄)₂], and NH₄[VO(SO₄)₂] have been prepared as crystals suitable for X-ray structure determination. In all structures sulfate acts as an unidentate ligand only toward a single vanadium atom. The structure of V₂O₃(SO₄)₂ consists of a threedimensional network of pairs of cornershared VO₆ octahedra with one terminal oxygen atom each, and SO₄ tetrahedra. All oxygen atoms of the sulfate ions are coordinated. NH₄[VO(SO₄)₂] and K[VO(SO₄)₂] are isostructural. VO₆ octahedra with one terminal oxygen atom and pairs of sulfate tetrahedra form infinite chains by corner sharing. The chains are weakly interlinked to layers. The sulfate ions are distorted towards planar SO₃ molecules and single oxygen atoms attached to vanadium. This structural detail gives an explanation for the mechanism of the reversible reaction K[VO(SO₄)₂] ? K[VO₂(SO₄)] + SO₃ at 400°C. Raman spectra of the compounds have been recorded and interpreted with respect to their structures. Crystal data: V₂O₃(SO₄)₂, monoclinic, space group P2₁/a, a = 947.2(4), b = 891.3(3), c? 989.1(4) pm, β = 104.56(3)°, Z = 4, 878 unique data, R(R_w) = 0.039(0,033); K[VO(SO₄)₂], orthorhombic, space group P2₁2₁2₁, a = 495.3(2), b = 869.6(9), c = 1 627(1)pm, Z = 4, 642 unique data, R(R_w) = 0,11(0,10); NH₄[VO(SO₄)₂], orthorhombic, space group P2₁2₁2₁, a = 495.3(1), b = 870.0(2), c = 1 676.7(4)pm, Z = 4, 768 unique data, R(R_w) = 0.088(0.083).     

Isopiestic determination of the osmotic and activity coefficients of aqueous Lu2(SO4)3 at 25°C

Osmotic coefficients have been measured for aqueous Lu₂(SO₄)₃ solutions from 0.12402 to 0.89631 mol-kg^–1 at 25°C by use of the isopiestic method; these measurements extend into the supersaturated molality region. Since there was a lack of activity data for Lu₂(SO₄)₃ solutions at lower molalities, they were approximated by equating them to results for La₂(SO₄)₃ from freezing temperature depression measurements. The combined osmotic coefficients were then used to derive mean molal activity coefficients for Lu₂(SO₄)₃ solutions. The osmotic coefficients decrease to 0.307 as their minimum value and the mean molal activity coefficients decrease to 0.0069. When these activities were combined with our previously reported solubility of 0.6260±0.0017 mol-kg^–1 for Lu₂(SO₄)₃·8H₂O, a thermodynamic solubility product of 2.3×10^–10 was obtained. This value yields the Gibbs energy of formation G _f ^° (Lu₂(SO₄)₃·8H₂O, cr)=–5518.9±16.4 kJ-mol^–1.     

Ion dissociation and conduction of Nafion/modified oligo(oxyethylene) composite films

In order to improve the ionic conductivity of solid polymer electrolyte by controlling ion(alkali metal ion)–dipole(ether oxygen) interaction, two kinds of modification were adopted on oligo(oxyethylene) (OOE). One is the capping of terminal hydroxyl groups of OOE with methyl or acetyl groups. The other is the replacement of the center ethylene group of OOE with methylene or propylene group. Ion–dipole interaction was analyzed by measuring the ion dissociation, ion conduction and T_g of Nafion/modified OOE composite films. The modification of the end groups was more effective than that of the center group in increasing ionic conductivity. The methyl group is superior to the acetyl group as the end group of OOE for lithium ion conduction.     

An aqueous thermodynamic model for a high valence 4∶2 electrolyte Th4+−SO 4 2− in the system Na+−K+−Li+−NH 4 + −Th4+−SO 4 2− −HSO 4 − −H2O to high concentration

An aqueous thermodynamic model that is valid from zero to high concentration is proposed for the Na⁺–K⁺–Li⁺–NH ₄ ⁺ –Th⁴⁺–SO ₄ ^2– –HSO ₄ ^– –H₂O system. The model is based on the aqueous ion-interaction model of Pitzer and coworkers. The thorium sulfate complex species Th(SO₄)₂(aq) and Th(SO₄) ₃ ^2– are also included in the model. The final thermodynamic model presented here accurately predicts all reliable thermodynamic data, including solvent extraction and solubility data, for the Na⁺–K⁺–Li⁺–NH ₄ ⁺ –Th⁴⁺–SO ₄ ^2– –HSO ₄ ^– –H₂O system to high concentration. The aqueous thermodynamics of high-valence (3:2, 4:2), electrolytes are complicated by very strong specific ion interactions or ion pairing in dilute solution and by an effective redissociation of aqueous complex species at high concentration. Methods of treating these complications, in terms of valid aqueous thermodynamic models, are discussed in detail for the high-valence Th⁴⁺–SO ₄ ^2– –H₂O system.     

Tandem synthesis of silver nanoparticles and nanorods in the presence of poly(oxyethylene)-amidoacid template

Sequential formation of silver nanoparticles (AgNPs) and nanorods from the reduction of AgNO₃ was affected by a poly(oxyethylene)-amidoacid (POE-amidoacid) in aqueous solution. The requisite POE-amidoacid, consisting of –(CH₂CH₂O)_n– segments with amide and carboxyl groups, was simply prepared via amidation with trimellitic anhydride of a poly(oxyethylene)-monoamine (POE-amine) of molecular weight (M_w) ∼2000 g/mol. The POE-amidoacid afforded AgNPs as small as 5 nm in diameter, which gradually (over a period of months) self-assembled into nanorods that were 10–15 nm in width and 30–50 nm in length. The hierarchical formation of Ag species occurred only at ambient temperature, but Ag aggregates formed above 50 °C. The process could be monitored by UV absorption at 420 and 380 nm for AgNPs and nanorods, respectively, and by transmission electron microscopy (TEM) for the nanorods. Fourier transform infrared (FTIR) and tapping-mode atomic force microscopy (TM-AFM) analyses revealed that the structurally tailored POE-amidoacid was indeed multifunctional: it reduced Ag⁺, stabilized the obtained Ag⁰ species, and served as a template for the tandem formation of AgNPs and nanorods.     

Synthesis of polymers in aqueous solutions: Polyaddition of bis(oxazolines) with dithiol in aqueous solutions

Polyaddition of bis(4-mercaptophenyl) sulfide ( BMPS ) with m-phenylenebis(2-oxazoline) ( MPBO ) proceeded very smoothly in the mixtures of aprotic ploar solvents such as N-methyl-2-pyrrolidone ( NMP ) with water to produce the corresponding poly(amide–sulfide) with high molecular weights at 90°C under nitrogen. The reaction of BMPS with MPBO , p-phenylenebis(2-oxazoline), and 1,4-butylenebis(2-oxazoline) was also examined in water under the same conditions, and it was found that the reaction proceeds successfully to give the corresponding poly(amide–sulfide)s with high molecular weights. These results mean that water along as well as the mixed solvents of aprotic polar solvents such as NMP with water can be uses as suitable reaction media for the polyaddition of bis(oxazolines) with dithiol to synthesize poly(amide—sulfide)s with high molecular weights. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2711–2717, 1997     

Solute activity coefficients in dilute aqueous electrolyte mixtures. III. The ternary system HClO4+UO2(ClO4)2+H2O at 25°C

Isopiestic vapor pressure comparison measurements were conducted with the three-component system HClO₄+UO₂(ClO₄)₂+H₂O in the concentration range between I=0.05 and 1.9m. Analysis of the mixture composition and concentration dependence of the osmotic coefficients with the Scatchard neutral-electrolyte and ion-component methods and with the Pitzer ioncomponent methods gave equally satisfactory results. Prediction of the observed osmotic coefficients by two-component approximations was satisfactory, and the data agreed well with values estimated with a model based on the osmolal fraction. A fair concordance was also found between predicted solute activity coefficients from simple models and values derived from complete treatments which included interaction terms.     

Stereocomplex Mediated Gelation of PEG-(PLA)2 and PEG-(PLA)8 Block Copolymers

Stereocomplex mediated hydrogels have been prepared by mixing solutions of polymers of opposite chirality of either PEG-(PLA)₂ triblock copolymers or PEG-(PLA)₈ star block copolymers. The critical gel concentrations of the mixed enantiomer solutions were considerably lower compared to polymer solutions containing only the single enantiomer. Moreover, gel-sol transition temperatures were increased and gel regions were expanded due to stereocomplexation. Rheology measurements showed that stereocomplexed hydrogels based on PEG-(PLA)₈ have higher storage moduli compared to those based on PEG-(PLA)₂. Stereocomplexed hydrogels prepared from 13 wt% PEG-(PLA)₂ solutions in PBS showed a storage modulus of 0.9 kPa at 37 °C, while at similar conditions stereocomplexed hydrogels of PEG-(PLA)₈ showed a storage modulus of 1.9 kPa at 10 wt%.     

Study of cryostructurization of polymer systems VII. Structure formation under freezing of poly(vinyl alcohol) aqueous solutions

Rheological properties of the cryogels produced by freezing of concentrated aqueous solutions of poly(vinyl alcohol) have been studied. These properties were shown to depend on the polymer concentration in the initial solution, on PVA molecular weight, cryostructurization duration and temperature. Electron microscopy demonstrates the heterogeneous porous structure of these cryogels and the dependence of the observed pattern on the conditions of formation of the studied objects.     

铟在聚乙二醇-硫酸铵双水相体系中的分配

研究了稀散元素铟在有配合剂PAR（4－（2－吡啶偶氮）－间苯二酚）存在和无PAR存在的聚乙二醇PEG－（NH4）2SO4双水相体系中的分配行为。讨论了酸度、PEG分子量、PEG浓度及温度等因素对铟分配比的影响，发现酸度对分配比的影响最大，随着PEG分子量的增加及温度的上升分配比逐渐增大；随着PEG浓度的增加分配比逐渐减小。