Arvid Berge

Swelling of oligomer-polymer particles. New methods of preparation

Abstract The stabilization of polydisperse aqueous emulsions towards degradation by molecular diffusion is discussed. A new method for preparation of stable monomer emulsions by diffusion, based on the physicochemical principles underlying said stabilization, is described. After homogenization of a highly water insoluble compound with water and emulsifier, the dispersed phase is swollen with more than 200 times its own volume of monomer. With stable, finely dispersed monomer emulsions, the monomer droplets may become center for particle initiation even in case one applies a water soluble initiator. The kinetics of the polymerization of such emulsions is discussed in terms of the Smith-Ewart theory, taking into account that the monomer concentration at the reaction center decreases from the start of reaction. Polymer particles consisting of pure polymer are only capable of absorbing 0.5 to 5 times their own volume of low molecular weight compounds. Calculations based upon an extended Flory-Huggins equation predict that if the particles contain a substantial amount of an oligomer which is water insoluble and has a relatively low molecular weight, one may expect an enormous increase in the swelling capacity of such particles for monomer. Methods are described where the polymer particles have been swollen with monomer up to a v/v ratio of > 1000. The principles outlined above have been used to prepare monodisperse particles with very large sizes, including monodisperse, porous particles.

Monodisperse magnetic polymer particles: new biochemical and biomedical applications

The method of activated swelling of polymer particles developed by the authors allows the preparation of monodisperse spherical beads of predictable size from 1 to 100 microns in diameter. The polymer particles may be prepared from a number of different monomeric materials and with various morphologies including macroporous structures. The porous beads form the basis for magnetizable monodisperse polymer particles which have magnetic iron oxides distributed as small grains all through the volume of the beads. The magnetic particles are being used extensively for selective cell separation and for immunomagnetic separation within microbiology and molecular biology. A review of recent work within these fields is given. New methods for positive cell separation are announced.

Hydrophilic Monodisperse Particles as Solid-Phase Material in Immunoassays: Comparison of Shell-and-Core Particles with Compact Particles

Hydrophilic monodisperse shell-and-core particles with a density of 1.07 were superior to heavier compact particles as a solid-phase material for immunoassays. The shell-and-core particles formed a semistable suspension for 24 h and were easily collected by centrifugation. The hydroxyl groups of the particles were activated with two sulfonyl chlorides. The most reactive one, tresyl chloride, gave rapid chemical coupling of antibodies, whereas tosyl chloride favored a rapid hydrophobic adsorption which was followed by slow chemical coupling. The solid-phase sheep antirabbit IgG made was used as a separation agent in several immunoassays and gave solid-phase primary antibodies by immunoadsorption of rabbit antibodies.

Formaldehyde release from particleboard - evaluation of a mathematical model.

The formaldehyde release from particleboard under changing climatic conditions and with varying amounts of exposed particleboard was studied in a large climate chamber. A mathematical model was developed which describes the influence of the various parameters on the formaldehyde concentration in the atmosphere of a room containing particleboards. After determining the formaldehyde concentration under standard conditions by a laboratory method, the formaldehyde concentration under any other climatic conditions can be calculated. The mathematical relations presented in this paper are of model character, therefore, they cannot be transferred uneritically to every board system.ZusammenfassungDie Formaldehydabgabe aus Spanplatten unter wechselnden klimatischen Bedingungen und bei unterschiedlicher Plattenmenge wurde in einer großen Klimakammer untersucht. Es wurde eine mathematisches Modell entwickelt, das es ermöglicht, den Einfluß verschiedener Parameter auf die Formaldehydkonzentration der Raumluft eines mit Spanplatten bestückten Raumes zu erfassen. Hat man die Formaldehydkonzentration mit einem bestimmten Prüfverfahren unter Standardbedingungen festgestellt, so kann sie für beliebige andere Klimata durch Rechnung ermittelt werden. Die hier dargestellten mathematischen Beziehungen haben Modellcharakter; sie lassen sich deshalb nich unkritisch auf jedes beliebige Plattensystem übertragen.

Thermodynamics of Swelling of Polymer, Oligomer and Polymer-Oligomer Particles. Preparation and Application of Monodisperse Polymer Particles.

The treatment of the equilibrium distribution in various polymer-monomer or polymer-mixed solvent systems has most often been based upon the classical Flory-Huggins lattice theory and the extension of this theory by Morton to include the interfacial energy. Further developments of these theories have included the swelling of polymer particles with mixtures of different monomers, systems in which the continuous phase (water in the case of aqueous dispersions) is present in the monomer and polymer phases, and the swelling of oligomer and oligomer-polymer particles. Ugelstad et al. have shown experimentally and theoretically that oligomer particles and oligomerpolymer particles in aqueous dispersions are capable of absorbing monomer to an extent that are orders of magnitude higher than for pure polymer particles. This has led to development of emulsion polymerization procedures which allow preparation of highly monosized large particles in the range of 1–50 μm in diameter. Such particles have up to now found industrial application in liquid chromatography. The particles are furthermore used as standards for blood cell counters. Hydrophilic monosized particles prepared by the new methods are utilized in different immunoassays where they have been found to possess advantageous properties. The monodisperse particles have also founded the basis for the preparation of monosized magnetizable microspheres which have been applied for cell separation.

Excess antibody immunoassay for rat glandular kallikrein. Monosized polymer particles as the preferred solid phase material

The development of an excess antibody assay for rat glandular kallikrein is described. This assay permits immunological determination of kallikrein as well as a simultaneous specific measurement of kallikrein enzymatic activity. The assay is based on coupling of immunopurified anti-kallikrein immunoglobulin to a solid phase. In a first incubation step, kallikrein was bound to the immobilized antibody. Determination of kallikrein was subsequently done in a second incubation step; immunologically by addition of iodinated anti-kallikrein antibody, or enzymatically by a kallikrein substrate. Enzymatic quantification could also be followed by immunological measurements on the same sample. Comparison of Sepharose, cellulose, and acrylate based polymer particles proved the latter to be the best matrix in this assay. The main advantage of the polymer particles was the low non-specific binding of labelled antibody.

Characterization of crosslinked, macroporous, monosized polymer particles

Macroporous, monosized poly(meta-divinylbenzene) and poly(para-divinylbenzene) beads have been prepared by the two-step activated swelling method with toluene or 2-ethylhexanoic acid as pore-forming agents. The type of divinylbenzene isomer as well as the type of porogen has a large effect on both physical and chemical properties of the monodisperse beads. Large pores are obtained with 2-ethylhexanoic acid as porogen while beads prepared in the presence of toluene consist of only small pores and exhibit a shrinking behavior upon drying. The beads have considerable amounts of residual vinyl groups at the end of polymerization, as determined by bromination and Fourier transform IR analysis. The morphology and texture of the particles have been investigated by scanning electron microscopy and atomic force microscopy.

Friedel–crafts reactions of pendant vinyl groups in macroporous monosized poly(meta-divinylbenzene) and poly(para-divinylbenzene) particles

Residual vinyl groups in macroporous monosized polymer particles of poly(meta-DVB) and poly(para-DVB) prepared with toluene and 2-EHA as porogens have been reacted with aluminum chloride as Friedel–Crafts catalyst with and without the presence of lauroyl chloride. In the reaction between aluminum chloride and pendant vinyl groups a post-crosslinking by cationic polymerization takes place. A reaction occurring simultaneously is the addition of HCl to the double bonds. The progress of these reactions was studied by characterization of vinyl group conversion, pore size distribution, specific surface area, morphology, and swelling behavior. In the reaction with aluminum chloride the poly(para-DVB) particles showed a substantially higher conversion of pendant vinyl groups than the particles made of poly(meta-DVB) independent of porogen type. The reaction with aluminum chloride led to a reduced swelling in organic solvents and an increased rigidity of the particles prepared with toluene as porogen. This is confirmed by an increase in the total pore volume in the dry state and a change in the pore size distribution of these particles. Also in the reaction with lauroyl chloride poly(para-DVB) particles have shown a higher conversion of pendant vinyl groups than poly(meta-DVB) particles and the acylation was almost complete at the early stage of the reaction. The swelling in organic solvents is reduced as a result of the incorporation of acyl groups into the particles prepared with toluene as porogen.

Biomedical Applications of Monodisperse Magnetic Polymer Particles

The method developed by Ugelstad and coworkers1-3 for preparation of monosized polymer particles allows preparation of particles of any size from 1 to 100 µm with standard deviation in diameter ~ 1%. Also the method allows preparation of particles from a large number of monomers. Particles with highly crosslinked polymer of high mechanical strength, porous macroreticular particles and core and shell particles are prepared. The application of the porous macroreticular particles in fast protein liquid chromatography (FPLC)4 as marketed by Pharmacia is already well established and has in many cases led to very significant improvements in analysis and separation of complex protein mixtures.

Melamine-formaldehyde compounds—I The alkaline decomposition of methylol melamines and methoxymethyl melamines

Abstract The acid catalysed decompositions of trimethylol melamine (TMM), hexamethylol melamine (HMM), methylated trimethylol melamine (TMM-Me) and hexamethoxymethyl melamine (HMM-Me) have been investigated kinetically. The deompositions of TMM and HMM are subject to general acid catalysis. The results suggest that the activation of TMM and HMM takes place by addition of a proton to the N-atom in a side group. The more facile protonation of the N-atom in the triazine ring represents a deactivation. The results with HMM indicate that the hexasubstituted melamine compounds are considerably less basic than the less substituted compounds. The splitting of the ethers to give the corresponding methylols takes place by addition of a proton to the ether oxygen atom in the first step. In this case, also, the protonation at a N-atom in the nucleus represents a deactivation. The splitting of TMM-Me is subject to general acid catalysis. The decomposition of HMM-Me is specifically catalysed by H3O+ ions. The rate of decomposition of TMM-Me approaches an upper constant value as [H3O+] increases beyond 10−3 mole/1, whereas the rate of decomposition of HMM-Me increases markedly up to [H3O+] = 1 mole/1. While in moderately acid solution (pH ⩾ 3) TMM-Me decomposes 45 times faster than HMM-Me, HMM-Me decomposes 30 times faster than TMM-Me in 1 N HCl. The H3O+ catalysed decomposition of the ethers to methylol compounds is much faster than the subsequent decomposition of the methylol compounds to free formaldehyde. The difference in behaviour between the different types of ethers, as regards pH dependence and general acid effects, seems to have been overlooked in previous publications on methods for determination of methylol and ether groups.