Nonionic latices in aqueous media part 1. Preparation and characterization of polystyrene latices

A series of non-ionic polystyrene latices in aqueous media containing particles with a narrow size distribution have been prepared using a nonyl phenol poly(ehylene glycol) condensate as the surfactant, methoxy poly(ethylene glycol methacrylate) as the comonomer/stabilizer, and ascorbic acid/hydrogen peroxide as the initiator system. As a control synthesis for comparison with the above latex, a charge stabilized polystyrene latex was prepared, using an anionic surfactant and potassium persulphate as the initiator. Latices employing a combination of charge plus steric stabilization mechanisms were also prepared, in order to investigate the effect of the non-ionic surfactant and the comonomer/stabilizer. The particle size of the latices was measured by transmission electron microscopy, the surface charge density by conductimetric titration and the glass transition temperature of the polymer by differential scanning calorimetry. The latex prepared using non-ionic ingredients, showed no titratable charge and exhibited a profound lowering of the glass transition temperature, with respect to the charge stabilized latex. On the basis of these results, schematic models for the polymerization mechanism and the morphology of the latex particles are proposed.     

Nonionic latices in aqueous media

The rate of conversion of styrene into polystyrene by emulsion polymerisation has been investigated in the absence and in the presence of methoxy-polyethyleneglycol methacrylate, MeOPEGMA. The effect of adding MeOPEGMA at different stages of the polymerisation was also investigated. Additions at the beginning of the polymerisation and at the early stages gave a bimodal particle size distribution whereas late additions gave small particle size, monodisperse latices which were electrosterically stabilised. The latter materials were found to be colloidally stable to the addition of high concentrations of electrolyte and to freeze-thaw conditions.Part 3: Brit. Polymer J., 1987, 19:435     

非离子型表面活性剂对聚硅氧烷阴离子型乳液的耐电解质稳定性的影响

本文研究了非离子型表面活性剂对聚硅氧烷阴离子型乳液的耐电解质稳定性的影响。十二烷基聚氧乙烯醚C12H25(OCH2CH2)nOH(n=6.3,C12E6.3)能提高乳液的氯化镁临界凝聚浓度。乳液的表面化学性质和乳液粒子表面上表面活性剂的组成表明C12E6.3与十二烷基苯磺酸之间存在着协同作用,组成了混合界面膜。根据DLVO理论对C12E6.3提高乳液耐电解质凝聚稳定性进行了解释。     

Synthesis of Nonionic Aroxylsulfonyl Carbamates

Novel aroxylsulfonyl carbamates containing polar head or core type were synthesized from the action of aroxysulfonylisocyanate on oligooxyethylmonomethylated ethers or glycols without solvent. At room temperature the reaction occurs rapidly with satisfactory yields. The synthetic pathway of isocyanate derivatives is achieved in a one-pot reaction in order to use low price commercially available compounds such as phenolic derivatives and chlorosulfonylisocyanate as starting materials. This new class of nonionic compounds contains one aromatic part and one polar part. All these compounds are monodisperse, that is, they include a perfectly defined number of oxyethylene units. The synthesis and characterization of these new series of carbamates are described.     

Studies of particle-particle interactions using polystyrene latices and time-average light scattering

Dilute dispersions of monodisperse negatively-charged polystyrene latex particles, radii 161 Å, have been examined by time-average light scattering at various latex volume fractions and electrolyte concentrations. The latter were varied from the low value produced by maintaining mixed bed ion-exchange resin beads in the systems (ca. 10^–5 mol dm^–3) to the value of 5×10^–3 mol dm^–3 obtained by the addition of sodium chloride. From angular scattering measurements determinations of the structure factors were made; these were produced as a consequence of the particle-particle interactions in the system. By extrapolation of the structure factor to zero scattering angle, values were obtained for the osmotic compressibility and hence the osmotic pressure of the systems as a function of the latex volume fraction. It was found that the experimental data obtained could be interpreted in terms of a hard-sphere model for the particle-particle interaction. Good agreement was obtained provided that the particles were assigned a hard-sphere radius which was determined by the electrostatic repulsion between the particles.     

微量热法研究非离子型表面活性剂微乳液

用微量热法研究了由正十六烷／正己醇／水／烷基聚氧乙烯醚组成的微乳液中水的状态，对微乳液中水的模式对热效应的影响进行了解释。在微乳液具有异常流变性的水油比范围内，测定了体系在负触变性状态恢复期间的热效应。     

Partially fluorinated thermally responsive latices of linear and crosslinked copolymers

A series of thermally responsive copolymers of N-isopropylacrylamide (NIPAAM) with a fluorinated hydrophobic comonomer, either hexafluoroisopropylmethacrylate (HFIPMA) or 2,2,3,3,4,4-hexafluorobutylmethacrylate (HFBMA) and a hydrophilic comonomer, methacrylic acid (MAA), were synthesized by emulsion polymerization. The chemical structures of the copolymers were studied by the IR technique. Dynamic light scattering (DLS) showed that aqueous latices of the copolymers exhibited swelling–deswelling changes typical to PNIPAAM; the degree of swelling as well as the temperature at which the polymers collapse depended on the chemical structure of the comonomers. Endotherms related to the contraction of the polymers were studied by differential scanning calorimetry (DSC). A combination of DLS and DSC results revealed that the hydrophobic and hydrophilic units in the copolymers strongly affected the swelling behavior, as well as the local environment of the PNIPAAM chains. The comonomer HFIPMA increased the hydrophobicity of NIPAAM, reduced the swelling, and caused coagulation of the copolymer of NIPAAM and HFIPMA at temperatures above the critical temperature. Hydrophobicity of HFIPMA also affected the rheological properties of the latex. The HFBMA comonomer increased the swelling of the latex particles. Methacrylic acid added into the associating copolymers made the copolymers to show polyelectrolyte behavior with an increase of swelling and a decrease of the enthalpy change upon the collapse. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2141–2152, 1998     

非离子表面活性剂浊点的研究进展

综述了非离子表面活性剂浊点的理论模型,介绍了非离子表面活性剂的浓度与外加无机电解质、极性有机物,表面活性剂、聚合物对浊点的影响规律和机理,以及在常压下浊点高于100℃时非离子表面活性剂的浊点估测方法。     

Preparation of polymethylmethacrylate latices in non-polar media

The dispersion polymerization of methylmethacrylate stabilized by poly(12-hydroxy-stearic acid) in hydrocarbon media has been investigated. Unlike earlier results [7] it was found that stable latex particles can be prepared in the initial monomer concentration range 8.5 % to 34 %. To obtain stable particles varying amounts of stabilizer were used.     

Compression studies on aqueous polystyrene latices

An apparatus, that allows simultaneous measurements to be made of excess osmotic pressure and optical diffraction of polymer colloid dispersions, has been constructed. Results are reported for monodisperse polystyrene latices at several salt concentrations. An interesting feature of the results is a clear indication of a co-existence region occurring with particles of 182 nm diameter in sodium chloride concentrations of 10^–4 mol dm^–3     

非离子型微乳状液制备均分散硫化镉

近年来,半导体胶体CdS溶胶或悬浮液已引起人们极大兴趣,其原因在于它的光电性质,特别是它的光化学性质及光催化性质。而上述性质均与CdS胶体粒子的大小和形状密切相关,所以作为光能转换及光催化反应的硫化镉溶胶不仅纯度要求高,而且对粒子的尺寸、形状及均匀性的要求也银严格。目前,主要用水解法、苯硫酚法及用阴离子型表面     

盐类和温度对非离子型表面活性剂溶液粘度的影响

研究在各种盐类存在下,温度对非离子表面活性剂(OP类)溶液粘度的影响,发现相对粘度的对数值与1/T呈线性关系,从直线的斜率可得活化自由能ΔG′。由热力学关系式可计算粘性流体的活化焓ΔII′和活化熵ΔS′。用所得热力学函数对胶束型态的转化进行了讨论。     

Adsorption of lysozyme and α-lactalbumin on poly(styrenesulphonate) latices 2. Proton titrations

A study on the titration behaviour of hen's egg lysozyme (LSZ) and milk α-lactalbumin (LAC) is presented. Titration curves for the proteins in their native state, after exposure to denaturing agents, and adsorbed on poly(styrenesulphonate) (PSS) latices are compared. Titrations of the proteins in the presence of guanidinium hydrochloride and sodium dodecyl sulphate (SDS) show that electrostatic interactions, more than alterations in the chemical environment, affect the dissociation of the charged groups on the protein molecule. The titration of adsorbed (apo)-LAC is similar to that of the SDS-denatured state, independent of the surface coverage. The titration of LSZ depends on the degree of coverage, suggesting different modes of adsorption. The two conformers of LAC, i.e. apo-LAC and Ca-LAC, are compared to test the influence of the structural stability of the protein on the titration behaviour. In solution, the two conformers of LAC titrate differently, but after adsorption on to a PSS latex surface the titration behaviour is practically the same. This points to a similar adsorbed state, with expulsion of the Ca²⁺ ion from the Ca-containing form.     

Ion exchange in carboxylated latices — AUC studies using sedimentation and density gradient techniques

Crosslinked highly carboxylated acrylic latices with narrow particle size distributions were prepared by emulsion polymerization and characterized carefully by different AUC techniques (particle size distributions and particle density measurements). The acid form of those latices was neutralized with metal oxides like MgO, CaO, ZnO, or PbO in order to obtain the corresponding salt form of the latices which again were characterized carefully. The kinetics of the ion exchange between latex particles were studied by mixing, for example, the acid and the salt form of the latices monitoring the density distribution of the latex particles by density gradient ultracentrifugation. With all latices the hydrogen-metal ion exchange tends to be a complete one provided this process is given a sufficiently long exchange time. Theoretical models are provided which yield a qualitative explanation of the experimental data.     

Dual-phase solid polymer electrolytes prepared from styrene–butadiene copolymer latices

A new dual-phase solid polymer electrolyte system has been proposed. In this system, a network of ion pathways is formed in a low-polarity, host polymer matrix. A series of electrolytes were prepared from styrene-butadiene copolymer latices with dissolved lithium salts. Polymer films were formed from these latices, and then impregnated with γ-butyrolactone (γ-BL) or γ-butyrolactone/dimethoxyethane mixture (γ-BL/DME), giving latex polymer electrolytes. The ionic conductivity of the polymer electrolyte system increased with increasing solvent content, although a distinct percolation threshold was not measured. Ionic conductivity also increased with the use of DME cosolvent, with the highest conductivity being 1.4 × 10^?4S/cm. Complex impedance diagrams are discussed. The diagrams show significant deviations from the ideal. TEM/SEM observations are consistent with the desired dual-phase morphology. © 1993 John Wiley & Sons, Inc.     

醇对非离子型表面活性剂浊点的影响

研究了醇对非离子型表面活性剂浊点的影响，发现直链醇的碳原子数小于４时随着其在表面活性剂中含量的增加浊点上升；当碳原子数大于４时，则随着醇含量的增加浊点下降。醇的构型对浊点起着重要作用。     

非离子表面活性剂增敏三元离子缔合物光度法测定微量银

研究并建立了非离子表面活性剂聚乙二醇辛基苯基醚(Tx-100)胶束增敏离子缔合物分光光度法测定微量银的分析方法。实验结果表明,在表面活性剂存在下,方法的灵敏度比未增敏体系提高了近5倍,络合物稳定性也大大增加。方法的最佳酸度是pH=4.0,银浓度在0～0.4mg·mL-1符合比耳定律。以EDTA为掩蔽剂,只有Br-、I-、CN-、S2-有干扰。方法用于人工合成样品和显影废液中微量银的分析,准确度和精密度令人满意。     

Small angle and quasi-elastic neutron scattering studies on polymethylmethacrylate latices in nonpolar media

Poly(methylmethacrylate) particles stabilised by poly(12-hydroxystearic acid) in a hydrocarbon medium provide, as a polymer latex, a useful system for investigating the properties of a sterically stabilised concentrated dispersion. In the present work these latices were investigated by small angle coherent neutron scattering and by quasielastic incoherent scattering. The former technique was used to probe the dimensions of the surface layer of poly(12-hydroxystearic acid) and to determine the diameter of the core particle of poly(methylmethacrylate) using dilute dispersions. In concentrated dispersions it was used to determine the structure factor. The latter was compared with that expected for an interacting system of hard spheres and reasonable agreement obtained. The quasielastic technique was used to probe the translational diffusion of the poly(12-hydroxystearic acid) molecules on the surface and the diffusion of the total particles in the concentrated systems.     

Thermodynamic and Dynamic Properties of Micellar Aggregates of Nonionic Surfactants with Short Hydrophobic Tails

The densities and viscosities of binary aqueous mixtures of poly(ethylenoxide)hexanols [C₆H₁₃(OCH₂CH₂)_mOH, C₆E_m] (m= 3, 4, and 5) have been studied in the micellar composition range. For the same surfactants the self-diffusion coefficients in mixtures with heavy water have been determined by the spin-echo pulsed field gradient method. The volumetric data are interpreted by means of the phase separation model, and values of the CMC, volume change, and standard free energy change of micellization are obtained. From the viscosity data the hydration numbers of the surfactant hydrophilic head in the micellar state are computed; they are in agreement with those obtained from HDO self-diffusion data. The surfactant self-diffusion data are used to calculate the apparent micelle radius and the aggregation number. The micellization parameters obtained for the different surfactants are compared and discussed.