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.     

Localization of carboxyl groups at surface layer of carboxylated polymer emulsion particles by alkali treatment

For the purpose of localizing carboxyl groups from inside to particle surface, styrene — butyl acrylate — methacrylic acid (74.3/17.0/8.7, mol ratio) terpolymer emulsion was kept under pH 9 at different temperatures. The amount of carboxyl groups at the particle surface, As, was remarkably increased by the alkali-treatment above 35 °C. On the other hand, As value of the alkalitreated emulsion was decreased by keeping under ph 3 above 45 °C, although in the case of the original emulsion without the alkalitreatment, it was not changed by the acid-treatment. These results suggest that a part of polymer segments which have ionized carboxyl groups is dragged out at the surface by an increase in the affinity of the groups against water, and the dragged segments turn back into the inside again when the carboxyl groups are deionized.Part 97 of the series Studies on Suspension and Emulsion.     

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     

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.     

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.     

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.     

The effect of pH on emulsion polymerization of styrene in the presence of an amphoteric emulsifier

An emulsion polymerization of styrene in the presence of an amphoteric emulsifier of the betaine type; N,N-dimethyl-n-laurylbetaine (LNB), has been studied at various pH values. The relationships between the physicochemical properties of LNB aqueous solutions, the emulsion polymerization process and the characteristics of the synthesized latex particles were studied under various pH conditions. The polymerization rate and the particle number concentration decreased with increasing pH of LNB aqueous solution and changed in shape at both ca. pH 4 and pH 8–10. The properties of LNB aqueous solution also changed with the pH and changed in shape at the same pH as that of the emulsion polymerization. These pH values were in good agreement with the pH at which the LNB molecule changed its ionic form. The number of synthesized latex particles was proportional to the number of LNB micelles in the solution, below pH 10. The particle size of the synthesized latex particles and the molecular weight of the latex polymers also changed with the properties of LNB aqueous solutions, accompanying the change of the ionic form of LNB molecules.     

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.     

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     

XPS analysis (ESCA) of the surface composition of poly(styrene/2-hydroxyethyl methacrylate) microspheres produced by emulsifier-free emulsion polymerization

Polymer microspheres composed of various compositions of styrene and 2-hydroxyethyl methacrylate (HEMA) were produced by batch emulsifier-free emulsion polymerization. The HEMA content at the surface, [HEMA] _s , of the microspheres powdered by freeze-drying was determined by both quantitativeC ^1s /O ^1s analysis andC ^1s peak shape analysis of the x-ray photoelectron spectroscopic spectra. When the HEMA content in the microsphere, [HEMA] _p , was less than about 5 mole%, the [HEMA] _s values determined by the two different methods showed good agreement. At [HEMA]_p above 5 mole %, [HEMA]_s values determined by the first method were about 15 mole % greater than those determined by the second. They both showed a similar tendency with the [HEMA] _s being higher than the [HEMA] _p , e.g., when [HEMA] _p was 1 mole %, [HEMA] _s was 11 mole %. The intensity of the satellite peak due to the ^* transition of the benzene ring of the styrene component decreased with an increase in [HEMA] _p , to zero at 5 mole % of [HEMA] _p . These results indicate that the HEMA component is localized at the surface.Part CVIII of the series Studies on Suspension and Emulsion.     

Formation of monodisperse poly(1-methacryloxybenzotriazole) particles by radiation-induced dispersion polymerization

Radiation-induced dispersion polymerization of 1-methacryloxybenzotriazole (MABt) in ethyl propionate starts as homogeneous mixture and the resulting polymer precipitates as spherical particles. Formation, size, and shape of polymer particles are strongly dependent on the initial monomer concentration. Three regions can be distinguished: formation of deformed particles at concentrations of 15 w/v-% MABt; formation of spherical particles at concentrations from 18 to 35 w/v-% MABt; no precipitation of polymer at concentrations of 40 w/v-% MABt. The spherical particles at 20 w/v-% MABt had a diameter of 0.54 ± 0.31 m for 3 kGy irradiation and 2.93±0.68 m for 30 kGy. The number distribution of the microspheres shows that the spherical particles with small sizes formed at low irradiation dose (low conversion) disappears with increasing irradiation dose because of multi-coating by newly produced polymer.     

An isotachophoresis for the microdetermination of potassium persulphate as initiator in emulsion polymerization

An isotachophoresis (IP) was applied to determine the decomposition rate of potassium persulphate (KPS) as initiator in emulsion polymerization, in comparison with conventional iodometry and ferrometry. For the exact determination, the latter methods needed several milliliters of the emulsion pipetted from the polymerization system, whereas IP did only a few microliters. Moreover, the amount of sulphuric acid produced as the decomposition by-product was simultaneously determined by IP, which is impossible for iodometry and ferrometry.Part CIV 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.     

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.     

Asphalt-polyolefin emulsion breakdown

An analysis of factors controlling the stability of asphalt-polyolefin emulsions is given. From flocculation kinetics and changes in particle size distributions, it is concluded that the major cause of instability is due to Brownian coalescence followed by gravitational flocculation and creaming. A cyclical change in the particle size distribution, indicative of simultaneous flocculation and creaming, is observed only in the final stages of the emulsion breakdown.     

Aggregation phenomena in the suspension polymerization of VCM

In the suspension polymerization of VCM, insoluble polymer particles are formed inside the monomer droplets. The growth and aggregation of these particles are responsible for important polymer properties, such as porosity. It is well established that the most characteristic polymer particles, the primary particles, are of a narrow distribution with a size (diameter) ranging from 0.10–0.20 m. This work studied the formation of primary particles based on the aggregation phenomena that take place inside a monomer droplet. This was done by formulating a population balance equation, which was based on the following considerations: a) polymerization occurs in both the monomer and the polymer phases; b) there is continuous formation of the basic particles in the monomer phase; c) the growth of the polymer particles occurs as a result of both polymerization in the polymer phase and aggregation of the particles; d) the colloidal properties of the particles that are responsible for the aggregation phenomena were considered to be the net result of attraction and repulsion energies.It was shown that for particles carrying a constant charge it was not possible to predict the formation of primary particles of size 0.10–0.20 m. The particle size distribution had a mode diameter equal to the diameter of the basic particles. Consequently, the particle charge was allowed to vary in a way proportional to the particle radius raised to a power coefficient. For values of the coefficient greater than zero, i. e., when the particle charge increased during polymerization, the aggregation of the basic particles was efficient enough to result in the formation of large primary particles.     

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.     

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.     

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.