Hollow‐particle latexes: Preparation and properties

Abstract

Hollow‐particle latexes were prepared according to the following stages: (1) the preparation of the methyl methacrylate–methacrylic acid (MAA)–ethylene glycol dimethacrylate copolymer (I) latex, (2) the preparation of a shell (II) based on polystyrene or styrene–acrylonitrile–divinyl benzene copolymer polymerized onto copolymer (I) particles, and (3) the neutralization of the core (I) carboxyl groups with a base (NH4OH or NaOH) at temperatures close to the glass‐transition temperature of the polymer (II). The neutralization resulted in the expansion of the particles and formed water‐filled hollow particles. The microspheres had an overall diameter of 460–650 nm and a hollow diameter of 300–450 nm. Rheological studies and particle size measurements by transmission electron microscopy and dynamic light scattering of the copolymer (I) latex indicate that the maximum particle swelling occurred at an approximately equimolar MAA/base ratio. It was found that even without the neutralization of the MAA units, a small hollow formation in the latex particles occurred during stage 2 because one volume of the copolymer (I) retained about 8 volume parts of water. It was also discovered that the final hollow‐particle geometry after neutralization depends on the shell copolymer thickness and type as well as on the conditions during stage 3, that is, the time, temperature, base type, and concentration. The opacifying ability of the synthesized hollow particles was investigated in latex coatings. The opacifying ability values were generally in agreement with the hollow‐particle geometry. The only exception was related to the copolymer (I)/copolymer (II) ratio. The maximum hollow volume was obtained at this value equal to 1/8, whereas the highest opacifying ability was observed at 1/10. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1435–1449, 2001

Instability of hollow polymeric microspheres upon swelling

“…Note that deformed spheres having a shape similar to that shown in Fig. 2 were observed in experiment [2]. The instability can be avoided if the polymer shell is made of a material whose deformation diagrams have no descending regions or if we can exclude the system passage to such a descending region.…”

New Possibilities for Controlling the Morphology of Core-Shell Latex Particles During Emulsion Polymerization

“…We succeeded in solving this problem by enhancing the hydrophilicity of the shell copolymer through introduction of acrylonitrile (AN) units into its composition [14]. The desired effect is achieved by introducing no less than 25 wt % AN units into the copolymer.…”

Microgranules and Nanoparticles on Their Surfaces

“…Microgranules in the form of hollow spheres are of interest primarily as capsules for the storage and delivery of liquids and gases, the fundamental building blocks of photonic crystals, high-porosity materials for catalysis and sound insulation, low-loss dielectric materials, and supports for immobilization of nanoparticles on their outer and/or inner surfaces. The most widely used process for the preparation of hollow spheres is the fabrication of core/shell nanoparticles and subsequent removal of the core by calcination or dissolution, depending on the core composition [110][111][112][113].…”