Seeded Emulsion Polymerization Process Research Articles

EFFECT OF THE PHASE STRUCTURE EVOLUTION ON THE PROPERTIES OF FILMS FORMED FROM PBA/P(ST-co-MMA) COMPOSITE LATEX

A group of heterogeneous latexes poly(butyl acrylate)/poly(styrene-co-methyl methacrylate) (PBA/P(St-co-MMA)) were prepared by a semi-continuous seeded emulsion polymerization process under monomer starved conditions. The glass transition temperature (Tg) and the mechanical properties of the film formed from the composite latex changed with the evolution of the particle morphology. A photon transmission method was used to monitor the phase structure evolution of films which were prepared from core-shell PBA/P(St-co-MMA) latex at room temperature and annealed at 383 K above Tg of the polymers. In addition, the changes of the surface of the film formed from the composite latex with time at 383 K were observed by AFM. The evidence illustrated that the film formed from the core-shell latex particles was metastable. The rearrangement of the phases could occur under proper conditions.

Synthesis of hybrid colloidal particles: From snowman-like to raspberry-like morphologies

Colloidal particles with a controlled morphology combining both organic and inorganic parts were synthesized through a seeded emulsion polymerization process. Silica seed particles (from 100 to 400 nm in diameter) were first surface-modified by the adsorption of an oxyethylene-based macromonomer. Then, emulsion polymerization of styrene was carried out in presence of these particles, the formation of polystyrene nodules being highly favored at the silica surface in such conditions. While varying different experimental parameters, we have demonstrated that the ratio between the number of silica seeds and the number of growing nodules is a key parameter to control the morphology of the final hybrid nanoparticles.

Hybrid Dissymmetrical Colloidal Particles

Colloidal particles with a controlled morphology combining both organic and inorganic parts were synthesized through a seeded emulsion polymerization process. Silica seed particles from 50 to 150 nm were first surface-modified by adsorption of an oxyethylene-based macromonomer or covalent grafting of a trialkoxysilane derivative. Then, emulsion polymerization of styrene was carried out in the presence of these particles, the formation of polystyrene nodules being highly favored at the silica surface in such conditions. While varying different experimental parameters, we have demonstrated that the ratio between the number of silica seeds and the number of growing nodules is a key parameter in controlling the morphology of the final hybrid nanoparticles. For instance, in the particular case when this ratio was close to 1, dumbbell-like or snowman-like particles were obtained. Further selective surface modification of their silica moiety was also tested successfully, indicating a potential application of these hybrid particles as original building blocks toward supraparticulate assemblies.

Hydrophilicity of composite latex particles prepared with a particular seeded emulsion polymerization techniques

Various kinds of styrene–(meth)acrylate and (meth)acrylate lattices were prepared by conventional emulsion and seeded emulsion polymerizations as the references for the particular poly(methyl methacrylate-co-methyl acrylate)/poly(dimethylaminoethyl methacrylate-co-styrene) (PMMA-MA/PDM-ST) composite latex prepared by the regulated coagulation process during the seeded polymerization. The contact angle measurement—pendant droplets of distilled-deionized water being dropped on the dried films of these lattices—was performed in order to evaluate the improved hydrophilicity of the PMMA-MA/PDM-ST latex in comparison with those prepared by the conventional processes. The contact angle of the PMMA-MA/PDM-ST film was lower than those of the (meth)acrylate lattices due to the presence of DM-rich domains on the surface. The degree of wetting was controllable by changing the emulsifier content, co-monomer composition and the secondary monomer to seed polymer ratio (M/P). This unique seeded emulsion polymerization process can be applied for productions of outdoor paints.

From Raspberry-like to Dumbbell-like Hybrid Colloids through Surface-assisted Nucleation and Growth of Polystyrene Nodules onto Macromonomer-modified Silica Nanoparticles

ABSTRACTColloidal particles with a controlled morphology combining both organic and inorganic parts were synthesized through a seeded emulsion polymerization process. Silica seed particles (from 50 to 150 nm in diameter) were first surface-modified by the adsorption of an oxyethylene-based macromonomer. Then, emulsion polymerization of styrene was carried out in presence of these particles, the formation of polystyrene nodules being highly favored at the silica surface in such conditions. The ratio between the number of silica seeds and the number of growing polystyrene nodules appeared to be one of the key parameters to control the morphology of the final hybrid nanoparticles. When this ratio is close to 1, original hybrid dumbbell-like nanoparticles were mainly obtained.

Application of Small‐Angle X‐Ray Scattering as a Tool for the Structural Analysis of Industrial Polymer Dispersions

AbstractSmall‐angle X‐ray scattering (SAXS) was applied for the structural analysis of an industrial polymer dispersion in water (synthetic latex). For the preparation of the spherical latex particles under investigation, butadiene, styrene, and acrylic acid were used as monomers in a seeded emulsion polymerization process. The product is widely being used as a film‐forming agent for coatings in the paper‐making industry. It is demonstrated that by measuring the SAXS curves at different contrasts the overall particle size, mass density, polydispersity, and degree of heterogeneity can be estimated with a good accuracy, even without the necessity of a detailed fitting procedure. In particular, one obtains information about the spatial distribution of the various monomer units within the particles. Five isoscattering points could be observed in the contrast variation measurements and the scattering curves at all contrasts could be modeled with a fully consistent set of fit parameters. It is thus safe to conclude that the contrast agent sucrose does not affect the particle structure. A quantitative fitting of the experimental data set revealed that a significant amount of the poly(acrylic acid) is preferentially located in a thin shell of ca. 2 nm thickness around the core of the particles, that is mainly formed by poly(styrene‐co‐butadiene). The obtained results are fully consistent with additional measurements of the particle mass density, of the hydrodynamic particle radius by dynamic light scattering, and of the particle surface charge by potentiometric titration. It is concluded that SAXS is a highly useful tool for characterizing the structure of industrial latexes.SAXS data of a BAYSTAL® latex measured at various contrasts, the weight fraction of sucrose in the dispersion medium is given in the legend.magnified imageSAXS data of a BAYSTAL® latex measured at various contrasts, the weight fraction of sucrose in the dispersion medium is given in the legend.

Morphology of poly(butyl acrylate)/poly(styrene‐co‐methyl methacrylate) latex prepared by starved emulsion polymerization: II. Development of particle morphology

AbstractHeterogeneous latexes were prepared by a two‐stage seeded emulsion polymerization process under monomer starved conditions at 80 °C using potassium persulfate as the initiator and sodium dodecyl sulfate as the emulsifier. Poly(butyl acrylate) latexes were used as seeds. The second‐stage polymer was poly(styrene‐co‐methyl methacrylate). By varying the amount of methyl methacrylate (MMA) in the second‐stage copolymer, the polarity of the copolymer phase could be controlled. It was found that the latex particles displayed different morphologies depending on the monomer ratio. The amount of MMA had a significant effect on the evolution of morphology. The morphologies were observed by transmission electron microscopy. In addition, the evolution of the particle morphology was predicted by the mathmatical model for cluster migration. The model gave the same trends as the experimental results.© 2002 Society of Chemical Industry

Morphologies of polybutylacrylate/poly(styrene‐co‐methyl methacrylate) latex prepared by starved emulsion polymerization Part I. Thermodynamics equilibrium morphology

AbstractHeterogeneous latexes were prepared by a semicontinuous seeded emulsion polymerization process under monomer starved conditions at 80 °C using potassium persulfate as the initiator and sodium dodecyl sulfate as the emulsifier. Poly(butyl acrylate) latexes were used as seeds. The second‐stage polymer was poly(styrene‐co‐methyl methacrylate). By varying the amounts of methyl methacrylate (MMA) in the second‐stage copolymer, the polarity of the copolymer phase could be controlled. Phase separation towards the thermodynamic equilibrium morphology was accelerated either by ageing the composite latex at 80 °C or by adding a chain‐transfer agent during polymerization. The morphologies of the latex particles were examined by transmission electron microscopy (TEM). The morphology distributions of latex particles were described by a statistical method. It was found that the latex particles displayed different equilibrium morphologies depending on the composition of the second‐stage copolymers. This series of equilibrium morphologies of [poly(butyl acrylate)/poly(styrene‐co‐methyl methacrylate)] (PBA/P(St‐co‐MMA)) system provides experimental verification for quantitative simulation. Under limiting conditions, the equilibrium morphologies of PBA/P(St‐co‐MMA) were predicted according to the minimum surface free energy change principle. The particle morphology observed by TEM was in good agreement with the predictions of the thermodynamic model. Therefore, the morphology theory for homopolymer/homopolymer composite systems was extended to homopolymer/copolymer systems.© 2002 Society of Chemical Industry

Grafting behavior of n‐butyl acrylate onto poly(butadiene‐co‐styrene) latexes

The radical-induced grafting of n-butyl acrylate (BA) onto poly(butadiene-co-styrene) [(P(Bd-S)] latexes during seeded emulsion polymerization was studied. This P(Bd-S)/PBA rubber/rubber core/shell latex system exhibited unique grafting behavior as compared to other extensively studied rubber/glass core/shell latex systems, such as poly(butadiene-co-styrene)/poly(methyl methacrylate) [P(Bd-S)/PMMA], poly(butadiene-co-styrene)/polystyrene [P(Bd-S)/PS] and poly(butadiene-co-styrene)/poly(acrylonitrile)[P(Bd-S)/PAN]. These composite latexes were characterized by the formation of a highly grafted/crosslinked P(Bd-S)/PBA interphase zone generated during the seeded emulsion polymerization process. Although both of the individual core and shell polymers studied were “soft” themselves, the resulting P(Bd-S)/PBA composite latex particles were found to be rather “hard.” The formation of the interphase zone was studied by using techniques such as solvent extraction, differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:511–523, 1997

Morphology of poly(isoprene-co-styrene-co-methacrylic acid) latex prepared by two-stage seeded emulsion polymerization

Heterogeneous latexes were prepared by a two-stage seeded emulsion polymerization process at 80°C using potassium persulfate as the initiator and sodium dodecyl sulfate as the emulsifier. Poly(styrene-co-methacrylic acid) latexes containing varying amounts of methacrylic acid (MAA) were used as seeds. The second-stage polymer was poly(isoprene-co-styrene-co-methacrylic acid). By using different methods for the addition of the MAA and by varying the amount of MAA, the hydrophilicity of the polymer phases could be controlled. The morphologies and size distributions of the latex particles were examined by transmission electron microscopy. The latexes were in all cases unimodal, and had narrow particle size distributions. The particles displayed different morphologies depending on the polymerization conditions and monomer composition. The hydrophilic properties of the two phases in combination with the internal particle viscosity and crosslinking of the second phase during polymerization were found to be the major factors influencing the particle morphology. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1543–1555, 1997