A DSC study of PVAC-PMMA two-stage emulsion polymers

Core-shell polymer colloids were produced by a two-stage emulsion polymerization technique. The polymers thus formed were investigated by means of differential scanning calorimetry (DSC). The DSC thermograms show two separate glass transition regions of the core and the shell component with positions unchanged regardless of chemical composition. Increases in specific heat capacity at the glass transition temperature of both components are lower than theoretical values calculated from the net chemical composition. From these results, it is possible to estimate i) the chemical composition of the interfacial layer and ii) the interfacial layer thickness. This interfacial layer thickness is in the order of 2–7 nm.Part 7 of Polymerizations in the Presence of Seeds     

SAXS experiments on gel-spun polyethylene fibers

The properties of gel-spun polyethylene fibers hot-drawn to the maximum draw ratio depend on the spinning conditions. Different spinning conditions result in two types of structure in the paraffin oil containing fibers: an isotropic lamellar structure or a shish-kebab structure. Meridional SAXS experiments can identify the structure present. After extraction, these structures are still present but can be detected only in a more indirect way by SAXS experiments because of an excessive contribution of void scattering. During hot-drawing both structures are transformed into a more fibrillar structure. The shish-kebab structures can be drawn only to relatively low hot-draw ratios with an incomplete transformation of the lamellar overgrowth into the fibrils, as demonstrated by the presence of a meridional SAXS maximum/shoulder. This leads to relatively weak fibers. Lamellar structures can be drawn to high draw ratios by chain unfolding. A nearly complete transformation of the lamellae into fibrils is obtained and the fibers have excellent properties. The information about the morphology obtained by SAXS, DSC, WAXS, and SEM can be used to establish a relation between morphology and properties.     

Some aspects of polymer colloids I. Preparation and properties of different types of latex particles

The boundary region separating a latex particle from the surrounding medium has a great influence on the properties of latex dispersions. Four types of polystyrene and polystyrene/comonomer latices differing greatly in the structure of the boundary region were prepared. The first part of a series of papers reports on the preparation of the various latex dispersions. Mean particle sizes were obtained from simple turbidity measurements, quasi-elastic light scattering, and electron micrographs. The behavior of the particles in the centrifugal force field is a simple tool for detecting aggregation tendencies that are not directly related to salt stability. The BET-surface area agrees with the area calculated from the mean particle size when a sharp boundary and smooth surface is developed between the particle and the surrounding medium. In the case of particles with extended boundary regions (core/shell particles or particles with hairy envelopes), film formation reduces the specific surface area. Removal of soluble oligomers and polymers from the boundary region during subsequent treatments (purification and centrifugation before freeze-drying) can increase the surface area considerably.     

Polymer coatings onto anodized aluminum plate by anodic electrodeposition from alkali-swollen carboxylated acrylic emulsion

Polymer coating of an anodized aluminum plate was carried out by anodic electrodeposition from alkali-swollen ethyl acrylate-methyl methacrylate-methacrylic acid (45/45/10, mole ratio) terpolymer emulsion with dimethyl aminoethanol. The alkali-swollen state was controlled by heating time at 60°C prior to the elctrodeposition. The similar complicated behaviors were observed in the relationships between the alkali-swollen state and the primary current density, the current density after 2 min, the quantity of electricity, and the amount of polymer deposited. The appearance of coatings changed correspondingly with such behaviors. These results indicate that the properties of the coatings are complicatedly affected by the degree of alkali-swollen state.Part CXII of the series Studies on Suspension and Emulsion.     

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.     

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.     

Solvent-induced phase separation in polycarbonate blends PC/TMPC

Compatibility of the polycarbonates of bisphenol A (PC) and tetramethyl bisphenol A (TMPC) was studied in glassy films cast from CH₂Cl₂ at room temperature, and above the glass-transition temperature. Blends with different compositions and of different molecular weights were analyzed by DSC and small-angle neutron scattering (SANS). Solution studies were made with light scattering and microscopy. Some of the blend films were two-phased when cast at room temperature, but all films were one-phased in equilibrium above the glass transition. The SANS data demonstrated that phase separation in the cast films was not caused by inherent incompatibility of PC and TMPC, but was induced by the solvent CH₂Cl₂. The effect is caused by a closed miscibility gap in the ternary solution system PC/TMPC/CH₂Cl₂.     

Power law relaxation in an interpenetrating polymer network

Emulsion polymerized interpenetratingpolymer networks (IPN) of polyacrylate and polystyrene exhibit a power law relaxation over a wide frequency range. The response of the material to oscillatory shear, step sheaf strain and a constant stress can be described with a two parameter constitutive equation. The power law behavior was previously found in polymers at their critical state where molecular motions were correlated over large distances without intrinsic size or time scale.The effect of composition and crosslink density on the behavior of the material is studied. The behavior might be explained with the granular structure of the material.     

The effect of carrier solution on the particle size distribution of inorganic colloids measured by steric field-flow fractionation

The number average and the weight average particle diameters for suspended inorganic colloids found by the new technique of steric field-flow fractionation may be successfully used provided that the most suitable carrier solution is selected, in order to minimize the coagulation and adhesion phenomena.In the present work polydisperse, irregular colloidal particles of FePO₄·2H₂O (strengite) were studied. The average particle diameters were found to vary with the electrolyte concentration in the suspending medium. A strong variation of the number and weight average particle diameters was also observed with the quantity of the surfactant added to aquatic medium in order to increase colloidal stability. The influence of the electrokinetic charge of the FePO₄·2H₂O particles in relation to the surface charge of the material of the column employed, on the particle size measured was investigated. The proper carrier solution for minimizing coagulation and adhesion phenomena in the FePO₄·2H₂O colloidal particles was found to contain either 1.5% (v/v) detergent FL-70 and 0.1 MKNO₃ or 0.5% (v/v) detergent FL-70 and 0.033 MNa₂SO₄.     

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.     

Development of new hydrophilic polymer supports based on dimethylacrylamide

A survey of the development of hydrophilic resins based on dimethylacrylamide (DMA) is presented. It describes the preparation of DMA-based resins by suspension copolymerization of DMA and acrylamide-based crosslinking and functional monomers. Swellability data for a number of DMA-based resins are tabulated, demonstrating that the resins swell to approximately the same extent in dichloromethane as they do in water, methanol, dimethylformamide or dimethylsulphoxide, but they swell only slightly or not at all in tetrahydrofuran. Typical chemical reactions employed for quantitative estimation or derivatization of resin-bound functional groups, including those involving intra-resin crosslinking, are discussed. The development of composite polymer supports, in which the DMA-based polymer is supported on kieselguhr particles or an amphiphilic ion exchange polymer is supported on DMA-based resin beads, is also covered briefly.     

X-ray scattering study of molecular order in a liquid crystal-side group polysiloxane

The molecular structure of a polysiloxane with phenyl benzoate mesogenic side groups was investigated in an x-ray scattering study in the partially crystalline, smectic and nematic phase, and in the melt. In the crystalline phase polymer molecules have the form of straight ribbons with a double-comb-conformation. A bilayer structure is built up by regular stacking. Layers are the dominating structure element not only in the crystalline and smectic phase, but also in the nematic phase, and even in the isotropic melt. Layers are planar in the smectic phase and curved in the nematic phase, with an asymmetric distribution of the normal vectors about the director. In the isotropic melt there is evidence for the occurrence of clusters with layer-like short-range order.     

Preparation of micron-size monodisperse polymer microspheres having cationic groups

Micron-size monodisperse crosslinked polymer microspheres having chloromethyl groups were prepared by seeded copolymerization of styrene, divinylbenzene, and chloromethylstyrene in the presence of 2.1- monodisperse polystyrene seed particles produced by dispersion polymerization. The modification reaction of chloromethyl groups on the surfaces with polyamines such as triethylenetetramine and ethylenediamine was carried out. From the measurements of potential and the amount of chloride ion released, the introduction of a large number of cationic groups at the surfaces was confirmed.Part CXXXI of the series Studies on suspension and Emulsion.     

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     

Scattering function and the dynamics of phase separation in polymer mixtures under shear flow

The phenomenological mean-field theory describing concentration fluctuations and spinodal decomposition of binary mixtures of long flexible macromolecules is generalized to mixtures under steady shear flow. This shear flow leads to a partial orientation and stretching of the coils, as well as to an anisotropic deformation of concentration fluctuations. Generalizing the approach of Onuki and Kawasaki, we obtain the collective scattering function describing these concentration fluctuations in the mixture under shear flow. Both the steady-state situation in the one-phase region and the initial stages of spinodal decomposition for concentrations inside of the spinodal curve are considered.Contributed paper delivered at the Tagung der Deutschen Physikalischen Gesellschaft, Fachausschuß Polymerphysik, Berlin, March 30–April 3, 1987.     

A small-angle neutron scattering study on polydisperse silica spheres coated with polyisobutene

Neutron-scattering studies at small angles are performed on dilute dispersions of small, polydisperse silica spheres coated with polyisobutene in mixtures of h₁₂ and d₁₂-cyclohexane. The contrast variation method is applied to reveal the internal structure of the compound particles. For a detailed interpretation of the scattering curves, it is assumed that the particles consist of spherical silica cores with concentric PIB-layers into which solvent molecules can penetrate. Also the polydispersity of the particle cores is taken into account. Model calculations fit the experimental curves fairly well except for the curves near the matching point, and at higher wavevectors, where experimental errors are relatively large due to the smallness of the scattering of the particles compared to that of the background.     

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.     

Preparation of micron-size monodisperse polymer particles having highly crosslinked structures and vinyl groups by seeded polymerization of divinylbenzene using the dynamic swelling method

Micron-size monodisperse polystyrene/polydivinylbenzene (PS/PDVB) composite particles having highly crosslinked structures and vinyl groups were prepared as follows. First, 1.9 m-size monodisperse PS seed particles produced by dispersion polymerization were dispersed in ethanol/water (70/30, w/w) solution which dissolved divinylbenzene (DVB) monomer, benzoyl peroxide as an initiator and poly(vinyl alcohol) as a stabilizer. The PS seed particles were swollen with a large amount of DVB monomers to 4.3 m in diameter while keeping good monodispersity by the dynamic swelling method, where water was slowly added, continuously, with a micro feeder into the dispersion. And then, the seeded polymerization of the absorbed DVB was carried out.Part CXXXV of the series Studies on Suspension and Emulsion     

Light scattering study of solution properties of bovine serum albumin,insulin, and polystyrene under moderate pressure

Brillouin scattering experiments have been performed on very dilute solutions of bovine serum albumin (BSA) in pH=4.7,I=0.1 M NaCl; insulin in pH=7.5,I = 0.1 M NaCl and polystyrene latex suspensions in aqueous medium at room temperatureT = 20₁ °C. The samples were first characterized by quasi-elastic light scattering (QELS) to determine the translational diffusion coefficient (D _T), hydrodynamic radius (R _H), and polydispersity of each of the samples at normal pressure. Subsequently, the samples were subjected to Brillouin scattering studies where the spectrum of the scattered light was analyzed by using a piezo-electric scannend five-pass Fabry-Perot interferometer. The hydrostatic pressure (P) acting on the samples was varied in the range from 1B to 825 B in steps of 100 B each. The pressure dependence of the measured sound velocityV _s (P) could be least square fitted tov _s (P)=A₀ +A ₁ P +A ₂ P ² with experimental error (± 1 %). This data has been interpreted consistent with an earlier work within the framework of modified Tait's equation of state and presumption of linear pressure dependence of the adiabatic bulk modulus in the moderate pressure regime.