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     

Deposition of polymer latices on grafted Nylon 6 fiber

Deposition of polymer latices on a grafted Nylon 6 fiber was studied as a function of pH and the degree of grafting. The latices were polystyrene (PS), styrene/acrylamide copolymer (P(St/AAm)) and styrene/acrylic acid copolymer (P(St/AA)). The deposition of the latices on the grafted fiber decreased in every case with increasing pH and no deposition was observed at alkaline pH. The grafting of fiber with acrylic and methacrylic acid reduced the deposition of P(St/AAm) and P(St/AA) latices but had no influence on the deposition of PS latex. The relation between the deposition rates and the interaction energy at acidic pH indicates that the deposition of PS latex on the grafted fiber mainly depends on the electrostatic interaction. These results suggest that the expansion of water-soluble polyelectrolyte layer on the surface of grafted fiber plays an important role on the deposition.     

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     

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.     

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.     

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.     

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.     

SAXS study of core-shell colloids

Polymeric core-shell systems were produced by a two-stage emulsion polymerization technique under fixed conditions: i) monodisperse seed latex with a sufficiently high particle number; ii) starved monomer-II addition; iii) water-soluble initiator; iv) incompatibility of core and shell polymer. From electron micrographs, it is not possible to determine where the second polymer is located within these two-stage emulsion polymers. The internal structure of the particles can be detected by small-angle x-ray scattering. The results indicate that; i) the emulsion polymerization process takes place in a small surface layer region of the seed particles, and ii) a small interfacial layer exists between the core and shell polymer.Part 6 of Polymerizations in the Presence of Seeds     

Film formation with latex particles

The coalescence of latex particles is investigated through small-angle neutron scattering and electron microscopy. The particles are made of a soft polymeric core protected by a hydrophilic membrane, and they are dispersed in water. This dispersion is spread on a substrate, and water is removed to form a dry film. As the membranes of neighboring particles come into contact, they may break up to allow fusion of the particle cores. This is found to occur when the membranes are made of short-chain surfactant molecules; then all hydrophilic material is expelled to the film surface or to large isolated lumps. Alternatively, the membranes may remain until the film is completely dry; this is found to occur when they are made of hydrophilic polymers which are grafted onto the core. Hence, the fusion of particles is controlled by the connectivity of membranes.This work used the neutron beams of ILL in Grenoble and LLB in Saclay     

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.     

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.     

Participation of electrolyte cations in albumin adsorption onto negatively charged polymer latices

The participation of electrolyte cations in the adsorption of bovine serum albumin (BSA) onto polymer latices was investigated. The latices used were hydrophobic polystyrene (PS), and hydrophilic copolymers, i.e., styrene (St)/2-hydroxyethyl methacrylate(HEMA) copolymer [P(St/HEMA)] and styrene/acrylamide (AAm) copolymer [P(St/AAm)]. Three kinds of electrolyte cations (Na⁺, Ca²⁺, Mg²⁺) were used as the chloride. The amount of BSA adsorbed in every cation medium showed a maximum near the isoelectric point (iep, pH about 5) of the protein. The amounts of BSA adsorbed onto copolymer latices (except in the acidic pH region lower than the iep) were considerably smaller than that onto PS latex because of the steric repulsion and the decrease in the hydrophobic interaction between BSA and copolymer latices. In the acidic pH region, there was little difference in the amount of BSA adsorbed in every cation medium. However, in the pH region higher than the iep, the amounts of BSA adsorbed (particularly onto PS latex) in divalent cations (Ca²⁺ and Mg²⁺) media were relatively greater compared with that in a monovalent (Na⁺) one. This result was interpreted on the basis of the differences in such effects of electrolyte cations as dehydration power, suppression of the electrostatic repulsion, and binding affinity to BSA molecule. Ion Chromatographic estimation of the amounts of electrolyte cations captured upon BSA adsorption (in pH > 5) revealed that divalent cations were incorporated into the contact interface between the latex and BSA molecule so as to prevent the accumulation of anion charge and facilitate the protein adsorption.     

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.     

Surfactant-free emulsion polymerization of styrene using crosslinked seed particles

The aim of this research was to prepare a monodisperse polystyrene latex without surfactants adsorbed at the particle surface. Conventional polymerization formulations usually lead to large amounts of oligomers. Furthermore, they are characterized by a low reproducibility with respect to particle size. This was overcome by using a seed latex that was crosslinked in order to overcome dissolution in the monomer phase. By adjusting the seed concentration, any desired particle size in the range 0.5–1.2 m could be obtained. The monodispersity was very good.     

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     

Influence of a magnetic field on radicalic polymerization of butyl methacrylate

Butyl methacrylate polymerization, through various procedures, i.e., bulk, solution and emulsion studies in the presence and absence of a magnetic field was studied. The influence of the magnetic field was observed on the development of the reactions, and also on some properties of the synthesized homopolymers. The behavior of the reaction's occurrence, with and without the magnetic field was compared. The homopolymers obtained were characterized from the viewpoint of their stability.     

Theoretical study of dielectric behavior of microcapsule suspensions with distributed drug release rate

Theoretical consideration is made concerning the dielectric behavior of aqueous suspensions of W/O-type microcapsules containing aqueous electrolyte solutions, especially concerning distribution effects of the electrolyte release rate on the dielectric behavior.It is shown at first that the distribution of the release rate causes electrical conductivity of the capsule interior. Next, it is deduced, in the light of a theory of the interfacial polarization, that the distribution characteristics of the capsule interior's electrical conductivity are closely related to those of the relaxation time for a dielectric relaxation exhibited by the suspensions. Several formulas are derived to describe the relation between the distribution characteristics of the release rate and those of the relaxation time.     

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.     

Estimation of distribution of vinyl groups in micron-sized monodisperse polymer microspheres by bromine titration method

The distribution of vinyl groups in polystyrene/poly(styrene-divinylbenzene) (PS/P(S-DVB)) composite microspheres produced by seeded copolymerization of S and DVB in the presence of 2.1-m monodisperse PS seed particles was estimated from the amount detected with bromine titration method as a function of the reaction time under various conditions.Part CXXIII of the series Studies on Suspension and Emulsion.