Preparation of hemispherical poly(4‐vinylpyridine‐co‐butyl acrylate)/poly(styrene‐co‐butyl acrylate) composite microspheres by seeded preswelling emulsion polymerization

Abstract

ABSTRACT:Seeded preswelling emulsion polymerization was carried out by using monodispersed poly(4-vinylpyridine-co-butyl acrylate) [P(4VP-BA)] particles as the seed, and styrene and butyl acrylate as the second-stage monomers under different polymerization conditions, to obtain hemispherical polystyrene (PST)-rich-P4VP-rich microspheres. Prior to polymerization, toluene was added into the preswelling system together with the second-stage monomers. It was found that, with the increase of the amount of toluene, the particle morphology showed a tendency toward desirable hemispherical structure, and the colloidal stability of composite latex was improved. When the weight ratio of toluene/seed latex was increased up to 7.5/40 (g/g), the stable hemispherical latex could be obtained. However, when toluene was not added, the coagulum formed on the wall of the reactor during polymerization, and the composite particles with multiple surface domains (such as sandwich-like, popcorn-like) were formed. In addition, the final morphology of composite particles was influenced by the polarity of the seed crosslinker and the hydrophilicity of the second-stage initiator, which could affect the mobility of poly(styrene-co-butyl acrylate) [P(ST-BA)] chains. The morphology development during the polymerization was investigated in detail, and a schematic model was derived to depict the formation mechanism of hemispherical P(4VP-BA)/P(ST-BA) composite microspheres. The results revealed that the mobility of the P(ST-BA) chains influenced the diffusion of the P(ST-BA) domains on the surface of the P(4VP-BA) matrix. When the mobility of the P(ST-BA) chains allowed small-size P(ST-BA) domains to coalesce into one larger domain, complete phase-separated morphology (hemisphere) could be achieved.

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“…Phase separation of two or three different polymers in one spherical particles from emulsion polymerization has been used for other polymeric hemispheres. Du et al16,17 and Han et al18 prepared micron and submicron‐sized polymer particles with different morphologies by seeded dispersion or emulsion polymerization. The produced latex exhibited a wide variety of particle morphologies such as core‐shell, hemispherical, and inverted core‐shell structures.…”

Monodisperse polystyrene microspheres prepared by dispersion polymerization with microwave irradiation

“…In the last decades, monodisperse microspheres have been used in a variety of applications in biomedical treatment, instrument calibration, chromatography, and other areas 1, 2. Many preparation methods for monodisperse polymer microspheres have been studied,3–9 such as emulsifier‐free emulsion polymerization, successive seed emulsion polymerization, multistage swollen emulsion polymerization, and dispersion polymerization. For nearly monodisperse particles in the range of 200–500 nm, excellent results can be obtained through conventional emulsion polymerization and through emulsifier‐free emulsion polymerization.…”

Preparation and characterization of biotinylated and enzyme‐immobilized heterobifunctional latex particles as nanobio devices

“…Depending on the hydrophilic or hydrophobic nature of the monomers, as well as the monomer conversion rate, a range of morphologies can be developed with this approach. The hemispherical poly(4‐vinylpyridine‐ co ‐butyl acrylate)/poly(sty rene‐ co ‐butyl acrylate) composite latex particles18 and, furthermore, the hemispherical poly(2‐hydroxylethyl mathacrylate‐ co ‐methyl methacrylate)/poly(styrene‐ co ‐glycidyl methacrylate) composite latex particles with bifunctional groups19 were successfully prepared by the addition of an organic solvent together with a secondary monomer before the seeded polymerization stage. The addition of an organic solvent is supposed to decrease the polymerization locus viscosity and enhance the mobility of the polymer chain, leading to the desired latex particles with a thermodynamically favorable structure.…”