Stabilizers In Emulsion Polymerization Research Articles

Synthesis and Characterization of EC / BA / VAc Hybrid Latexes via Pre-Emulsified Semi-Continuous Seed Emulsion Polymerization

Hybrid latexes containing ethyl cellulose (EC), vinyl acetate (VAc) and butyl acrylate (BA) were prepared by pre-emulsified semi-continuous seed emulsion polymerization. Influences of some synthetic parameters on the stability of emulsion polymerization were investigated. The emulsion polymerization is optimum with emulsifier 3 wt%, OP-10/ SDS 1/1 and PVA 0.5 g. The emulsion average particle size increases with EC content increase.TGA and water absorption analysis show that EC/ BA / VAc hybrid latexes films containing more BA display better thermal stability and hydrophobicity. The EC/BA/VAc latex shows good biodegradation, flexility property and is suitable for slow-release material of environmental-friendly coated fertilizer.

Stability of Emulsion Polymerization of New Fluorinated Acrylate Emulsion and Its Characterization

The new fluorinated acrylate emulsion was synthesized by using the intermediate perfluorous nonene and 2-hydroxyethyl methacrylate as the staring reactants via semi-continuous seeded emulsion polymerization. The structures, glass transition temperature, thermal property and water repellency of the fluorinated acrylate emulsion were characterized with FTIR, differential scanning calorimetry, thermal analysis, and contact angle meter. Influences of many factors such as the theoretical solid content, the temperature of the emulsion polymerization on the stability of the emulsion polymerization, the added amount of emulsifiers and the added amount of the initiator were studied. Results show that the stability of the emulsion polymerization is fairly good when the theoretical solid content is below 30% and the reaction temperature is 80°C and the added amount of emulsifiers and the initiator are 6.0–8.0% and 2.0% respectively. In comparison with the acylate emulsion, the thermal stability of the fluorinated acrylate emulsion is decreased but the water repellency of the fluorinated acrylate emulsion is greatly increased.

Molecular Weight and Tacticity of Oligoacrylates by Capillary Electrophoresis - Mass Spectrometry

Oligo(acrylic acid) efficiently stabilizes polymeric particles, especially particles produced by reversible addition–fragmentation chain transfer (RAFT) (as hydrophilic block of an amphiphilic copolymer). Capillary electrophoresis (CE) has a far higher resolution power to separate these oligomers than the commonly used size exclusion chromatography. Coupling CE to electrospray ionization mass spectrometric detection unravels the separation mechanism. CE separates these oligomers, not only according to their degree of polymerization, but also according to their tacticity, in agreement with NMR analysis. Such analysis will provide insight into the role of these oligomers as stabilizers in emulsion polymerization, and into the mechanism of the RAFT polymerization with respect to degree of polymerization and tacticity.

Hybrid emulsifiers enhancing polymerization stabilities and properties of pressure sensitive adhesives

AbstractIn this study, a series of (anionic and nonionic) emulsifiers were investigated to prepare acrylic pressure sensitive adhesives (PSA) with core‐shell structure by semicontinuous emulsion polymerization. The cloud point of different emulsifiers was characterized to explain the emulsifier effects on the emulsification ability. It was interestingly found that the hybrid emulsifiers (anionic coupling with nonionic) with optimized compositions could enhance the stability of emulsion system and improve the properties of PSA compared with the mono‐emulsifier. The stability of emulsion polymerization, the appearance of the emulsion system and the properties of PSA were studied in details by changing the proportion and the content of hybrid emulsifiers. When the ratio of sodium dodecyl sulfate (SDS: anionic emulsifier) to polyoxyethylene alkyl phenyl ether (OP‐10: nonionic emulsifier) reached 2 : 1, the content of hybrid emulsifiers reached 3 wt % and the reaction temperature was around 80°C, a better emulsion system was obtained in terms of comprehensive properties. At this condition, the synthesized PSA demonstrated the good holding power and 180° peel strength properties with fair tacky property, which was promising for industrial applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Sulfonated Amphiphilic Block Copolymers: Synthesis, Self-Assembly in Water, and Application as Stabilizer in Emulsion Polymerization

Described is the synthesis of diblock copolymers generated via sequential atom transfer radical polymerization (ATRP) of poly(n-butyl acrylate) (PnBA) followed by chain augmentation with either sulfonated poly(2-hydroxyethyl methacrylate) (PHEMA) or poly(2-hydroxyethyl acrylate) (PHEA) blocks. ATRP of PHEMA or PHEA from PnBA macroinitiator was conducted in acetone/methanol 50:50 (v/v) and produced diblock copolymers of low PDI (<1.3). Hydroxyl functional groups were converted to sulfonate through esterification using excess 2-sulfobenzoic acid cyclic anhydride (SBA). TEM images of aqueous block copolymer solutions reveal an array of polymer micelle morphologies including monodisperse spheres, cylinders, and cylinder aggregates. Surface tensions and critical micelle concentrations appear to be dependent more on hydrophile structure as opposed to its length. Application of the synthesized block copolymers as stabilizers for batch emulsion polymerization of n-butyl acrylate showed the polymeric surfactant effectively stabilizes latex particles and produces a lower polydispersity when compared with commonly applied commercial emulsifiers.

ATRP and ROMP: Modular chemical tools for advanced macromolecular engineering

Well-defined graft copolymers were synthesized through the combination of two highly controlled polymerizations, ATRP (Atom Transfer Radical Polymerization) and ROMP (Ring-Opening Metathesis Polymerization). Synthesis of α-cyclobutenyl polystyrene- b-poly( tert-butyl acrylate) macromonomers was first performed by ATRP from an original initiator. ROMP of these macromonomers using Grubb’s generation II catalyst ((IMesH 2)(Cy 3P)RuCl 2(CHPh)) has allowed to synthesize well-defined graft copolymers with a polybutadiene backbone and polystyrene- b-poly( tert-butylacrylate) grafts. α-Cyclobutenyl polystyrene- b-poly(acrylic acid) macromonomers were prepared by acidolysis. An amphiphilic water-soluble α-cyclobutenyl polystyrene- b-poly(acrylic acid) macromonomer has been successfully employed as stabilizer in emulsion polymerization of styrene.

Particle Size Distributions in Electrosterically Stabilized Emulsion Polymerization Systems: Testing the “Mid-Chain-Radical” Hypothesis

It has been found [Thickett, S. C.; Gaborieau, M.; Gilbert, R. G. Macromolecules 2007, 40, 4710-4720] that rate and characterization data on the seeded growth of latex particles electrosterically stabilized by a hairy layer of anchored poly(acrylic acid) (pAA) can be qualitatively and quantitatively explained by mechanistic events involving mid-chain radicals (MCRs). A considerable range of data was found to be consistent with the supposition that these MCRs are formed by abstraction on the pAA during polymerization, and are slow to propagate but quick to terminate, and thus are a cause of radical loss; they may also undergo P-scission leading to secondary particle formation. Results are reported here for four additional types of experiments on the evolution of the particle size distribution (PSD) in these systems; all these experiments have the potential to refute the mechanistic hypothesis. The experiments comprise (i) evolution of the PSD of small particles, (ii) evolution of the PSD in a bimodal system (competitive growth), (iii) growth rates of separate experiments of small and large particles with the same total amount of pAA, and (iv) the amount of secondary nucleation (formation of small particles) with both pAA and also with poly(ethylene oxide) steric stabilizers. In each case, the data are qualitatively and quantitatively consistent with the predictions of the mid-chain-radical mechanisms and thus support the general applicability of this effect.

Particle Formation in ab Initio RAFT Mediated Emulsion Polymerization Systems

Amphiphilic, RAFT-capped, (acrylic acid)x(styrene)y diblock copolymers (x = 10, y ) 10, 5, 0) were synthesized and used as stabilizers in emulsion polymerization. Above the critical micelle concentration (cmc) of the diblocks and under appropriate reaction conditions micelles of the more hydrophobic diblocks were sufficiently nonlabile to be nucleated and act as seed particles for latex particle formation. The key parameters which allow control over the system are diblock hydrophobicity and initiator concentration. A homogeneous nucleation mechanism is most likely to operate below the cmc of the diblocks.

Extended Mechanistic Description of Particle Growth in Electrosterically Stabilized Emulsion Polymerization Systems

Polymeric (steric and electrosteric) stabilizers, based on water-soluble polymers such as poly(acrylic acid) and poly(ethylene oxide), are widely used to make surface coatings by emulsion polymerization and form a hairy layer which provides colloidal stability to the latex particles. It is shown by a combination of NMR and rate studies that the growth of these polymer colloids is dominated by a hitherto unsuspected combination of mechanisms: an abstraction reaction in the hairy layer which results in a radical on the water-soluble polymer which is slow to propagate but quick to terminate (Macromolecules 2006, 39, 6495-6504) and can also undergo beta-scission reactions. Termination with radicals which would otherwise lead to particle growth leads to radical loss, i.e., a slower polymerization rate, while beta-scission leads to radicals which can enter the water phase and cause secondary particle formation. Both of these effects are undesirable from a manufacturing point of view, and the newly discovered mechanism could be used to mitigate these undesirable features.

Preparation of Polystyrene Nanoparticles by Seed Polymerization Using Amphiphilic Random Copolymer Micelles as Seeds

In recent years, with the progress of techniques to prepare monodisperse fine polymer particles, various colloidal polymer particles are being used for practical applications, such as surface coatings, cosmetics, surface modifiers for photo films, and carriers for virus diagnosis. The sizes of the polymer colloidal particles prepared so far lie in the range from 10 nm– 10 mm depending on the method employed, which includes emulsion polymerization, microemulsion polymerization, miniemulsion polymerization, soap-free polymerization, dispersion polymerization, seed polymerization, and suspension polymerization. Among these methods, microemulsion polymerization is the most commonly-used technique to prepare polymer colloids with diameters <100 nm and narrow size distributions. Such small polymer particles are desirable for surface coatings because it takes only a short time for film formation and the particles can penetrate easily into porous substrates producing a film with good optical and mechanical properties. For pharmaceutical applications, colloidal polymer particles are expected to be used as a long-circulating drug delivery vehicle because particles smaller than 100 nm can be prevented from being detected by the human body’s reticuloendothelial system. However, a disadvantage of the microemulsion polymerization is that one has to use a large amount of a surfactant and a cosurfactant, i.e., nearly comparable amounts of a surfactant and a monomer may be necessary to be used. This often creates a problem of the purity of final products. In order to overcome this disadvantage, reactive surfactants are often used. These surfactants have a reactive group being able to react with a growing polymer chain during radical polymerization, resulting in a covalent incorporation of surface active molecules into the polymer chain. Another possibility to surmount this disadvantage is to use polymeric amphiphiles in place of conventional surfactant molecules. Although no covalent bonding is formed between the polymer amphiphile and resulting polymer particle, the polymer amphiphiles are strongly anchored to the surface of resulting particles through hydrophobic interactions. A number of studies using various amphiphilic block copolymers have demonstrated that they act as a powerful stabilizer in emulsion polymerization. In aqueous emulsion polymerization, hydrophobic block sequences can anchor onto the particle surface while the hydrophilic blocks extend into the water-phase and create a hydrophilic shell. Recently, the use of block copolymer micelles as a seed for emulsion polymerization has been proposed. With the seed polymerization, it may be possible to control the final number of the particles, and hence the size of the particles, whereas in the case of emulsion polymerization with use of conventional surfactants, the particle size depends on many parameters and thus the size can not easily be predicted. Comparing to amphiphilic block copolymers, amphiphilic random copolymers are much easier to synthesize, and one can choose a much wider range of monomers for their synthesis. Therefore, it should be worthy testing amphiphilic random copolymers for seed polymerization. There is a general trend for amphiphilic random copolymers to form micelle-like aggregates on the nanometer scale in aqueous solution due to mainly intramolecular hydrophobic associations, the association properties depending strongly

Mechanism of Radical Entry in Electrosterically Stabilized Emulsion Polymerization Systems

The kinetics and mechanism for the process of entering latex particles from the aqueous phase (radical entry) in electrosterically stabilized emulsion polymerization particles were studied. Polystyrene particles stabilized with differing lengths of poly(acrylic acid) chains bound to the surface were synthesized using RAFT-controlled radical polymerization techniques to ensure that the hydrophilic block was of low polydispersity; these latexes had been studied previously to examine the exit rate coefficient (k) in such systems via gamma-relaxation experiments. Particles stabilized with poly(acrylic acid) chains were shown to have a significantly lower average number of per particle (n) (and hence reaction rate) than that of equivalent systems stabilized with a conventional surfactant when used in seeded chemically initiated dilatometry experiments with styrene. Assuming that these emulsion systems obey second-order loss kinetics (i.e., an exited radical will re-enter another particle to either propagate or terminate, a phenomenon well accepted for styrene emulsion systems), the calculated entry rate coefficient (F) was significantly lower than that predicted by the control by aqueous phase growth mechanism for radical entry. Excellent agreement with the accepted entry model was found to occur when radical loss was assumed to be a first-order process with respect to (n) over bar (i.e., an exited radical is terminated in the aqueous phase) or if significant amounts of aqueous phase termination is introduced into the evolution equations of initiator-derived oligomers. These results may be explained by rapid transfer of radical activity to a poly(acrylic acid) chain on the surface, forming midchain radicals that increase the likelihood of termination events in the poly(acrylic acid) surface layer.

Rate-Controlling Events for Radical Exit in Electrosterically Stabilized Emulsion Polymerization Systems

The mechanism controlling radical loss by exit (desorption) in electrosterically stabilized emulsion polymerization particles was obtained from kinetic studies. Using RAFT-controlled radical polymerization techniques, polystyrene particles stabilized with differing lengths of poly(acrylic acid) chains bound to the surface were synthesized, with the hydrophilic block of low polydispersity, and of various degrees of polymerization. After removal of the RAFT agent, these latexes were used in seeded emulsion polymerization experiments with styrene, with the radical loss kinetics studied through the use of gamma-radiolysis dilatometry. The size of the particles is such that they follow zero-one kinetics, so the sole rate-determining step for radical loss is by exit. The rate coefficient for exit (k) of these latexes was obtained directly from the non-steady-state relaxation period. A significant decrease in k occurs (by a factor of 10) relative to ionically stabilized latexes of corresponding size, even for particles with very small hydrophilic layers. The value of k was smaller for latexes with greater length of the hydrophilic block, consistent with the hypothesis that exit in electrosterically stabilized systems is bound by a restricted diffusion through the hydrophilic polymeric layer on the surface. Modification of the Smoluchowski treatment for diffusion-control led rate coefficients to allow for diffusion through two different regions provides an expression for the rate coefficient of radical desorption out of a particle in these systems; semiquantitative agreement with experiment was obtained.

Control of Charge Densities for Cationic Latex Particles

We report a systematic investigation, together with a new method, on controlling cationic charge densities of latex particles. A covalently bonded charge density up to 100 μequiv/g was achieved on the basis of copolymers of glycidyl methacrylate (GMA) and butyl methacrylate (BMA) by either surfactant-free or nonionically stabilized emulsion polymerization, followed by the aminolysis of epoxy groups into quaternary ammonium groups. The cationic charge density was successfully controlled by adjusting the ratio between epoxy and amino groups. It was found that the formation of disadvantageous water-soluble polyelectrolytes was negligible. Cationic charges were also introduced to latex particles by using cationic azo initiators and/or copolymerization with cationic or amine-containing comonomers, but colloidal titrations showed that controlled formation of highly charged cationic latex particles without the formation of water-soluble polyelectrolytes was only achievable for the aminolysis approach.

Sterically Stabilized Emulsion Polymerization of Styrene

Batch emulsion polymerizations of styrene initiated by ammonium peroxodisulfate (APS) and 2,2'-azobisizobutyronitrile (AIBN) at a broad monomer concentration range were investigated. The role of the thick emulsifier layerformed by a nonionic emulsifier was investigated in the sterically stabilized emulsion polymerization of styrene. The polymerization rate vs. conversion dependence was characterized by two or three nonstationary rate intervals. The rate of polymerization increases with the monomer concentration and the increase is much more pronounced at lower monomer concentrations. The deviation from the micellar model was ascribed to the high oil-solubility of nonionic emulsifier and the chain transfer and desorption events. The values of desorption rate constant k' d e s for the sterically stabilized emulsion polymerization of styrene are slightly than those for the electrostatically stabilized emulsion polymerization of styrene. The number of polymer particles is nearly independent of the monomer concentration at ca. 20-30 % conversion. The dependence of the final polymer particle number vs. the monomer concentration is described by a curve with a maximum. The primary radical termination decreases the rate of polymerization, the number of polymer particles and the final conversion at the high concentration of both APS and AIBN. In the former APS system the less hydrophobic oligomeric radicals with depressed entry rate into particles appear. In the latter AIBN system the growing radicals are deactivated by primary radicals derived from AIBN. The similar polymerization behavior for both initiators results from the dominant chain transfer and radical exit events. The molecular weight of polystyrene is inversely proportional to the initiator concentration.

Sterically stabilized emulsion polymerization of 2-ethylhexyl acrylate

Batch emulsion polymerizations of 2-ethylhexyl acrylate (EHA) initiated by ammonium peroxodisulfate (APS), stabilized by the hydrophilic non-ionic emulsifier Tween-20, were investigated. Two non-stationary rate intervals appear at very high emulsifier concentration and four rate intervals at very low emulsifier concentration. The slight increase in the maximal rate with increasing emulsifier concentration is discussed in terms of the polymer gel formation. The average number of radicals per particle (¯n) mostly observed much below 0.5 is discussed in terms of the polymerization at the particle surface. The desorption rate constant k′des,N (Nomura modul, N-model) for the emulsion polymerization of EHA is ca. one order in magnitude larger than that reported for the emulsion polymerization of styrene. The stronger desorption of radicals suggests the O'Toole/Ugelstad model (k′des,T, T-model). The k′des,T values are one order of magnitude larger than the k′des,N ones. The formation of less stable monomeric (tertiary) radicals and the polymerization in the cross-linked particles (at the particle surface) induce desorption of radicals. The absorption rate of radicals (ρ a) by the particles decreases with increasing weight fraction of emulsifier. The close-packed interfacial layer forms a barrier for entering radicals. This includes the increased chain transfer to the emulsifier followed by the exit of emulsifier transferred emulsifier radicals to the continuous phase.

Sterically stabilized emulsion polymerization of styrene: Pseudo‐semicontinuous approach

AbstractThe sterically stabilized emulsion polymerization of styrene initiated by a water‐soluble initiator at different temperatures has been investigated. The rate of polymerization (Rp) versus conversion curve shows the two non‐stationary‐rate intervals typical for the polymerization proceeding under non‐stationary‐state conditions. The shape of the Rp versus conversion curve results from two opposite effects—the increased number of particles and the decreased monomer concentration at reaction loci as the polymerization advances. At elevated temperatures the monomer emulsion equilibrates to a two‐phase or three‐phase system. The upper phase is transparent (monomer), and the lower one is blue colored, typical for microemulsion. After stirring such a multiphase system and initiation of polymerization, the initial coarse polymer emulsion was formed. The average size of monomer/polymer particles strongly decreased up to about 40% conversion and then leveled off. The initial large particles are assumed to be highly monomer‐swollen particles formed by the heteroagglomeration of unstable polymer particles and monomer droplets. The size of the “highly monomer” swollen particles continuously decreases with conversion, and they merge with the growing particles at about 40–50% conversion. The monomer droplets and/or large highly monomer‐swollen polymer particles also serve as a reservoir of monomer and emulsifier. The continuous release of nonionic (hydrophobic) emulsifier from the monomer phase increases the colloidal stability of primary particles and the number of polymer particles, that is, the particle nucleation is shifted to the higher conversion region. Variations of the square and cube of the mean droplet radius with aging time indicate that neither the coalescence nor the Ostwald ripening is the main driving force for the droplet instability. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 804–820, 2003

Characterization of aqueous micellar solutions of amphiphilic block copolymers of poly(acrylic acid) and polystyrene prepared via ATRP. Toward the control of the number of particles in emulsion polymerization

A series of diblock, triblock and star-block copolymers composed of polystyrene and poly(acrylic acid) were synthesized by ATRP. The structure of the copolymers, the size of the blocks and the composition were varied, keeping however a short polystyrene block and a poly(acrylic acid) content larger than 60 mol% to allow solubility in alkaline water. Their micellization was studied by static and dynamic light scattering and the influence of their structural characteristics on the aggregation number, N agg, was examined at low salt concentration and alkaline pH. It was shown that micelles were in thermodynamic equilibrium and that N agg followed the power law N agg∼ N A −0.9 N S 2 (with N A, the total number of acrylic acid units in the copolymer and N S, the total number of styrene units), that is characteristic of amphiphile micelles formed from strongly segregated block copolymers. Moreover, N agg was independent of salt concentration in the investigated range. The same copolymers were previously used as stabilizers in emulsion polymerization [Macromolecules 34 (2001) 4439]. The final latex particle concentration, N p, was compared with N m, the initial micelle concentration. This enabled us to conclude that among the block copolymers studied, those with high acid content behaved like low molar mass surfactants. In contrast, those with low acid content formed stable micelles that could be directly nucleated to create latex particles, allowing a good control over N p.

New Reactive Block Copolymers as Stabilizers in Emulsion Polymerization

The synthesis and application of partly sulfonated polybutadiene-block-poly(ethylene glycol) copolymers as a new class of stabilizers for emulsion polymerizations is reported. These stabilizers combine all known stabilization mechanisms - electrostatic, steric, and electrosteric - together with the ability to participate in radical polymerization in a single molecule. It was found that the kind of initiator has a strong influence on the latex properties. Due to the polyelectrolyte nature of the new stabilizers, nonionic water-soluble poly(ethylene glycol) azo-initiators lead to smaller particles and less coagulum compared to water-soluble ionic initiators. The investigations surprisingly revealed that the poly(ethylene glycol)- azo-initiators accumulate in the small-particle-size fraction due to side reactions leading to their incorporation. The efficiency of the new stabilizers in a radical emulsion polymerization of styrene is highest if the degree of sulfonation is between 20 and 40%. Compared to low molecular weight stabilizers like sodium dodecylsulfate, the reactive block copolymer stabilizers are much more efficient especially at stabilizer concentrations below 0.1% relative to the mass of monomer. The almost complete covalent binding of the reactive polymeric stabilizers to the particles is proved by a combination of ultrafiltration, elemental analysis, GPC, and FT-IR investigations.

Block Copolymers of Poly(styrene) and Poly(acrylic acid) of Various Molar Masses, Topologies, and Compositions Prepared via Controlled/Living Radical Polymerization. Application as Stabilizers in Emulsion Polymerization

A series of well-defined diblock, triblock, and star-block copolymers composed of polystyrene and poly(acrylic acid) were synthesized by controlled/living radical polymerization and used as stabilizers in emulsion polymerization under alkaline conditions. The structure of the copolymers, the size of the blocks, and the composition were varied and their efficiency as stabilizers was correlated with their structural characteristics. The block length was varied from 10 to 30 units for the polystyrene block and from 13 to 266 units for the poly(acrylic acid) block. The copolymers appeared to be efficient stabilizers down to a block copolymer-to-monomer ratio of less than 0.5 wt %. From the comparison of the effect of the different structures and compositions, it was shown that the diblock copolymers were particularly efficient and that the optimal composition was about 10 styrene units and a maximum of 50 acrylic acid units. The triblock and star-block copolymers with external hydrophilic blocks did not behave much differently than diblock copolymers. In contrast, for the triblock copolymers with an internal hydrophilic segment, the efficiency strongly depended on the respective length of both blocks. The evolution of the number of latex particles, Np, with the concentration of surfactant was also studied and Np was shown to be proportional to [surfactant]α over a wide range of surfactant concentrations. The value of α was a function of the block copolymer composition irrespective of the individual block lengths: it was 1 for block copolymers with a poly(acrylic acid) content lower than 75 mol % and decreased to 0.4 when the hydrophilic content was increased. This trend was correlated with the exchange dynamics of the stabilizer. The results obtained with various initiator concentrations, temperatures, and ionic strengths corroborated the previous observation that the important point to explain the evolution of α with the copolymer composition was the competition between nucleation of the micelles and exchange of the block copolymers between the micelles and the continuously created polymer /water interfaces in the system. The time scale of this exchange (which is very fast for small-molecule surfactants) was on the same order of magnitude as the nucleation step for emulsion polymerizations carried out in the presence of block copolymers.

New reactive polymeric stabilizers for emulsion polymerization

Partly sulfonated polyolefins represent very effective reactive stabilizers for heterophase polymerizations. For instance, under proper chosen conditions, the efficiency of these stabilizers in emulsion polymerization, measured in particle surface area stabilized per gram surfactant, is higher than that for sodium dodecyl sulfate. 'H NMR measurements prove that the stabilizers will be almost completely covalently bound to the latex particles in the course of the polymerization.