Preparation of asymmetric polymer film by emulsion blend technique

Two kinds of anionic polymer emulsions, of which particle sizes were greatly different, were blended and then cast on a release-paper at 30 °C. One was poly(butyl acrylate) emulsion, 0.46n in diameter, produced by emulsifier-free emulsion polymerization, and the other was ethyl acrylate-methyl methacrylate (1/1, mole ratio) copolymer emulsion, 0.02m in diameter, produced by emulsifier-containing emulsion polymerization. The film produced had asymmetric surface properties: the air-side surface was nontacky and the bottom-side surface was tacky. The forming mechanism is discussed.     

Non-ionic emulsion polymerisation

A process, similar to conventional emulsion polymerisation, is described by which sterically stabilised polymer dispersions are made in water alone. Ionic initiators and surfactants are replaced by non-ionic species, and a copolymerisable stabilising macromonomer is also used. The dispersions have good stability to solvent addition, high shear rates and freeze-thaw cycling; however, the effectiveness of stabilisation depends on the nature of both the monomers and the macromonomers.     

The acceleration of decomposition of potassium persulfate in the presence of sodium dodecyl sulfate and polymer particles as a model of emulsion polymerization system

The decomposition rates of potassium persulfate (KPS) in aqueous solutions containing sodium dodecyl sulfate (SDS) in the presence of polystyrene or poly(methyl methacrylate) particles as models of emulsion polymerization systems were measured by isotachophoresis. Free SDS molecules dispersed in the monomolecular state had an ability to accelerate the KPS decomposition, but SDS molecules adsorbed onto the polymer particles did not accelerate it.Part CXX of the series of Studies on Suspension and Emulsion     

Production of anomalous polymer microspheres having uneven surfaces by “stepwise” heterocoagulation technique

Anomalous polymer microspheres having uneven surfaces were produced by stepwise heterocoagulation technique of small polymer particles (SPs) onto large polymer particles (LPs).SPs andLPs have surface charges opposite to each other in the emulsion states.SPs were produced by emulsion copolymerization of styrene and methacryloyloxyethyltrimethylammonium chloride, andLPs by emulsion terpolymerization of styrene, butyl acrylate and methacrylic acid, with nonionic emulsifier being used in both cases. Maximum covering ofLP bySPs was obtained under the conditions that both emulsions were blended without the coagulation at pH 3 at room temperature and then left stand to coagulate with each other at 70 °C for 4 h at pH 9.Part CXI of the series Studies on Suspension and Emulsion.     

Analysis of ″stepwise″ heterocoagulation process of small cationic polymer particles onto large anionic polymer particles using dynamic light scattering

In order to clarify in detail the process of the stepwise heterocoagulation of small polymer particles (SP) onto large polymer particles (LP), which we proposed to prepare anomalous polymer particles, the particle-size distribution in each step was estimated using dynamic light scattering.SP andLP have surface charges opposite to each other in emulsion states.SP were produced by emulsion copolymerization of styrene and methacryloyloxyethyltrimethylammonium chloride, andLP by emulsion terpolymerization of styrene, butyl acrylate, and methacrylic acid. Both emulsions in which nonionic emulsifier had been added were blended without coagulation and then the heterocoagulation was carried out by adjusting of the pH and heating.Part CXVII of the series Studies on Suspension and Emulsion.     

Distribution of emulsified monomers with different water solubility

The location and distribution of acrylic acid and styrene in emulsions made with a cationic surfactant, cetyltrimethylammonium bromide (CTAB), or an anionic surfactant, sodium dodecylsulfate (SDS), were determined with ultra-violet spectroscopy, conductivity, and potentiometry. In these systems, the acrylic acid remains in the aqueous phase near the micelle surface, whereas the styrene is located in the micelles or in emulsified droplets. In the absence of acrylic acid, some of the styrene is solubilized in the micelle interior and some is adsorbed at the micelle inner surface. Upon addition of acrylic acid, all the styrene is displaced to the center of the micelles. The interaction between acrylic acid and CTAB micelles is stronger than that between acrylic acid and SDS micelles. With CTAB, acrylic acid is adsorbed at the micelle surface, whereas with SDS, acrylic acid remains in the intermicellar solution. These differences can account for the differences reported in the emulsion copolymerization of acrylic acid and styrene using CTAB or SDS.     

Colloid-chemical properties of ruthenium dioxide in relation to catalysis of the photochemical generation of hydrogen

A colloid of RuO₂, prepared by thermal decomposition of RuCl₃, was characterized with respect to its colloid-chemical properties and assessed as a catalyst for photochemical production of hydrogen. The RuO₂ proved to be unstable towards coagulation, even under conditions of low electrolyte concentration and in the presence of polymers. The sol manifested the same electric double layer characteristics as many other oxide dispersions. The point of zero charge (p.z.c.) in indifferent electrolyte was positioned at pH 5.75.Adsorption of methylviologen (MV²⁺), a commonly used electron relay in photochemical systems, at the RuO₂/solution interface is mainly a result of attractive coulombic interactions (above the p.z.c. of RuO₂). No indications have been found that it adsorbs on RuO₂ under the operational conditions of hydrogen production. In the hydrogen production system, the mass transfer of methylviologen radicals (MV⁺) is a rate-limiting factor. As a function of the methylviologen concentration, the catalytic production of hydrogen passes through a maximum.Dedicated to Professor Dr. Dr. h. c. Armin Weiss on the occasion of his 60th birthday.     

Chemical deposition coatings from emulsifier-free anionic polymer emulsion onto anodized aluminum plate under stirring conditions

The chemical deposition from an anionic acrylic copolymer emulsion onto an anodized aluminum plate was carried out under various stirring conditions. The amount of polymer deposited was affected by the stirring rate. At higher stirring rates, the surface flatness of the obtained coating decreased, but the transparency (which was affected by the traces of bubbles, due to evolution of hydrogen gas from the surface of the plate in the deposition process) was improved. Under optimum stirring conditions an excellent coating having a flat surface and good transparency was obtained.Part CXVIII of the series Studies on Suspension and Emulsion.     

Drug-carrying latices for prolonged release of drugs

Dichlorophene was used as a model drug. Drug-carrying latex particles were prepared by soap-free emulsion copolymerization of dichlorophene acrylate with some hydrophilic methacrylate comonomers. The comonomers used affected not only the structure and colloidal stability of particles, but also the drug-activity of particles. Preliminary study of the drug activity revealed that highly hydrophilic latex particles were very stable and too inactive to be engulfed by amoebae and kill them. On the contrary, less hydrophilic particles carrying a large amount of drug can be an effective device to release drugs at a moderate rate to fight against extracelluar targets such as parasites.     

Transient adsorption of a tri(ethyleneglycol) polyacrylate on a plasmapheresis membrane

We study the adsorption of polyacrylate of tri(ethyleneglycol) in water on a plasmapheresis membrane, whose main constituent is a copolymer of acrylonitrile and methylmethacrylate. The amount of adsorbed polymer has a strong dependence on pH. Adsorbance is high at low pH and very low at high pH, while in the intermediate range the interfacial concentration is not a monotonic function of the solution concentrationC. Viscosimetry andUV adsorbance measurements in solution suggest the existence of plurimolecular structures, aggregates, or micelles. We propose a kinetic model, where these latter objects act as detergents at highC and, therefore, contribute to decreasing the interfacial concentration when increasingC.     

Radiation-induced crosslinking: III. Effect on the crystalline and amorphous density fluctuations of polyethylene

Small-angle x-ray scattering (SAXS) was used to determine density fluctuation in radiation-induced crosslinked polyethylene of varying degrees of crystallinity. Density fluctuation FL decreases with increasing crystallinity, while it increases linearly with increasing radiation dose or degree of crosslinking. By means of extrapolation, density fluctuations in the crystalline and the amorphous phasesFL _c andFL _a were obtained. At a given dose,FL _a is greater thanFL _c . The increase inFL _a with radiation is found to be much greater than that ofFL _c compared with the initial values at 0 Mrad,FL _c showing only a negligible increase event at 312 Mrad. The present findings suggest that crosslinks are not introduced within the crystalline phase; they take place primarily in the noncrystalline phase, in agreement with the conclusions reached previously on the basis of changes in crystalline and amorphous densities in irradiated polyethylene.Dedicated to Prof. Dr. W. Pechhold on the occasion of his 60th birthday     

Pecularities of the thermomechanical behaviour of ultra-high molecular weight linear polyethylene and its blends with linear polyethylene of normal molecular weight

Ultra-high molecular weight polyethylene UHMWPE (M _w=4 · 10⁶,I _s=O g/ 10 min), high density polyethylene of normal molecular weight NMWPE (I _s= 4.8 g/10 min) and their blends have been investigated by means of thermomechanical loading in constant and impulse regime. It has been established that after melting, NMWPE passes to a viscous-liquid state. After melting at 138 °C UHMWPE passes to a high-elastic state. The transition of UHMWPE to a viscous-liquid state takes place at temperatures higher than 180 °C and is accompanied by a high-elastic reversible deformation. The blends of UHMWPE with 10 and 20 mass % of NMWPE show a plateau on the thermomechanical curves, corresponding to a high-elastic state, in a shorter temperature range where the deformation is greater. The blends containing the higher percent of NMWPE show thermomechanical curves lacking such a plateau. All blends are characterized by a singular thermomechanically defined temperature of melting, which increases with increase of UHMWPE content. The existence of the high-elastic state in the curves of UHMWPE and its blends containing NMWPE less than 30 mass % above their melting temperatures is explained by the high degree of physical crosslinking of UHMWPE.     

Double percolation effect on the electrical conductivity of conductive particles filled polymer blends

Electrical conductivity of carbon black (CB) filled polymer blends which are incompatible with each other was studied as a function of the polymer's blend ratio. Transmission electron microscope (TEM) analysis shows that CB distributes unevenly in each component of a polymer blend. TEM photographs of phase structure of solvent extracted HDPE/PMMA blend and solvent extraction experiments of PMMA/PP blend detect the blend ratio at which the structural continuity of filler rich phase is formed. The electrical conductivity of polymer blends is found to be determined by two factors. One is the concentration of CB in the filler rich phase and the other is the structural continuity of this phase. This double percolation affects the conductivity of conductive particle filled polymer blends.     

Monolayers of 1,2,3-propanetriol esters at the air-water interface: two-dimensional phases and miscibility

Monolayers of two glycerol esters, 1-monooleoylglycerol and 1-monostearoylglycerol, were studied at the air-water interface in the 15–30C temperature range.From the experimental isotherms (surface pressure vs area and surface potential vs area) the surface phases of the esters were inferred.The miscibility between the two esters was discussed in relationship to the interfacial orientations and distributions and to the surface phases of the esters.The results obtained supported and strengthened the empirical rule on miscibility previously found [1–7], i.e., for non-ionic compounds the same interfacial orientation of the hydrophobic chains is required in order to have bidimensional miscibility between the components.     

Thermomechanical degradation of macromolecules

Extensional flow techniques are used to investigate thermomechanical scission of polymer solutions from ambient temperatures up to 150°C. We report precise central scission of chains beyond a critical fracture strain-rate. These results can be well accounted for by a Thermally Activated Barrier to Scission (TABS) model. We speculate upon the origin of degradation in simple shear flows and report novel results on degradation in porous media and ultrasonic sound fields, which contain dominant extensional components. Finally, we show how the nature and degree of degradation is affected by concentration and polydispersity. In semi-dilute entangled solutions, the degradation rates increase, are much higher for polydisperse solutions and the scission becomes progressively more random along the chain.Dedicated to Professor H. H. Kausch on the occasion of his 60th birthday     

Adhesion of a pair of polyethylene moldings by polyethylene gels

It was found that polyethylene gels in solvents such as benzene, toluene, xylene, decalin, tetralin, tetrachloroethylene, 1,1,2,2-tetrachloroethane, and chlorobenzene are effective for adhesion of a pair of polyethylene plates. In particular, the adhesion strength of polyethylene gels in decalin, tetralin and tetrachloroethylene was strong enough for practical use.Adhesive effect appears due to local dissolution of the surface of polyethylene plate in contact with the gel with increasing temperature, and subsequent recrystallization.     

Thermal and electrical studies of some polychelates

Polychelates of Mn(II), Fe(II), Co(II), Ni(II), and Cu(II) with 4,4′-dihydroxy-3,3′-diacetylbiphenyl-dithioxamide (DDBDO) have been prepared. Their structures were determined by visible reflectance spectroscopy and magnetic measurements in conjunction with thermogravimetric and IR measurements. Elemental analysis indicates a 1∶1 metal-ligand stoichiometry and the association of water molecules with the central metal. The decomposition temperature of the chelates is in the order Ni(II)>Fe(II)>Co(II)>Mn(II)>Cu(II). Thermal activation energies (E _a ), calculated with the help of Freeman-Carroll and Sharp-Wentworth methods, are in agreement with each other. The polychelates were found to be semiconductive, and the activation energy obtained from semiconducting behavior follows the order Co(II)>Ni(II)>Fe(II)>Cu(II)>Mn(II). The probable structure, such as six coordinated octahedral for Mn(II) and Fe(II) polychelates and four coordinated square planar for Co(II), Ni(II), and Cu(II) polychelates, have been suggested.     

Effect of pH on colloidal properties of native ovalbumin aqueous systems

The effect of pH on the molecular shape and dispersed state of native ovalbumin molecules in 20 mM phosphate and acetic acid buffer solutions has been studied using small-angle x-ray scattering (SAXS) and a rheological method The degree of association of the OA molecule at the 0.5% colloid system increases slightly with decreasing pH, i.e., 2.10 at pH 7.0, and 2.88 at pH 4.0, and the radius of the OA molecule decreases slightly with decreasing pH, i.e., 24.5 Å at pH 7.0, and 22.0 Å at pH 4.0.The OA colloid shows apparent yield stress and rigidity which are due to a certain ordered arrangement of the molecules. The yield stress and the rigidity increase abruptly at a pH value near to an isoelectric point (ca. pH 4.4). In the dilute system this increment is attributed to the change in the ordered arrangement or in the interparticle interaction, and not to the change in the association state of the OA molecules. The values of the yield stress and the rigidity remain almost constant over a wide concentration range and this feature (an auto-controlled mechanism) is kept over a certain range of pH.     

Binding of hexadecylammonium surfactants to water-soluble neutral polymers

The binding of hexadecyltrimethylammonium bromide and hexadecyldimethyl-2-hydroxyethylammonium bromide to neutral polymers was measured by a potentiometric titration method using surfactant selective electrodes. Binding to poly(vinyl alcohol) was slightly cooperative, while that to poly(ethylene oxide) lacked the co-operativity. Poly(vinyl pyrrolidone) did not bind them at all. Binding affinity as estimated by a distribution coefficient of the cationic surfactants between the bulk and polymer phases is about 2 orders of magnitude smaller than that of anionic sodium dodecyl sulfate. The heat of binding was estimated from the temperature dependence of the distribution coefficient and found to be endothermic. It is imagined that the cationic surfactants are simply partitioned between the aqueous bulk phase and the polymer coil phase which is regarded as aqueous organic mixed solvent.