Highly Filled Polystyrene/Laponite Hybrid Nanoparticles Prepared Using the Ad‐miniemulsion Polymerisation Technique

Abstract

The preparation of highly filled polystyrene/Laponite (PS/Lap) hybrid nanoparticles by the ad‐miniemulsion polymerisation technique, using conventional free‐radical polymerisation, is described. Laponite (Lap) is first modified with a polymerisable cationic surfactant. Then, using a second surfactant dispersions are prepared under sonication. A stable hybrid miniemulsion is obtained after mixing and co‐sonicating both miniemulsions. The polymerisation is conducted using an oil‐soluble initiator to obtain hybrid nanoparticles. PS/Lap hybrid nanoparticles are effectively prepared with clay contents as high as 50 wt%. TEM reveals that the highly filled hybrid latexes (≥30 wt%) exhibit encapsulated morphology with homogeneously distributed clay platelets.

Polymer Encapsulation of Single Clay Platelets by Emulsion Polymerization Approaches, Thermodynamic, and Kinetic Factors

“…In this way, successful encapsulation of clay was achieved. The group of Hartmann and Pasch uses a somewhat different approach where the monomer and the clay are in separate miniemulsions and then are co‐sonicated (ad‐miniemulsion polymerization technique) to achieve highly filled polymer clay nanoparticles . The process can be described as a polymerization in an adsorbed monomer layer created and stabilized as a miniemulsion.…”

“…As in polymer–polymer core shell particle formation, the interplay of thermodynamic and kinetic factors is also operating in clay encapsulation through (mini)emulsion polymerization. Looking from the starting point of miniemulsion polymerization, thermodynamically the clay has to be modified hydrophobically to make it miscible with the monomer initially . But the interfacial tensions change during the polymerization and the resulting morphology can still be armored latex particles.…”

“…After formation of a hemimicelle, the monomer (and sometimes also the initiator) is added under starved feed, keeping the viscosity of the particle as high as possible so as to prevent the thermodynamically most favorable morphology from forming, especially in the case of unmodified or partially modified clay. The same strategy is followed in the two‐step miniemulsion polymerization approach after creating seed particles with miniemulsion polymerization . In the case of unmodified clay platelets, the question is how in the initial stage of the polymerization a hydrophobic layer of polymer is created around the clay platelet .…”

Design and Preparation of Highly Filled Water‐Borne Polymer–Gibbsite Nanocomposites

“…Polymer–clay nanocomposites with a solids content as high as 50 wt% have been reported in the literature, but most of them were obtained with a relatively low filler content (≤3 wt%); only a limited number of publications were dedicated to the preparation of highly filled polymer–clay particles . These studies indicated that the compounds used for hydrophobization of clay and the size of the clay platelets can affect the maximum filler content and that the use of larger amounts of clay platelets may result in less colloidal stability because of an increase in ionic strength of the water phase . It has also been observed that the morphology of the resulting nanocomposites was affected by the filler amount .…”

“…These studies indicated that the compounds used for hydrophobization of clay and the size of the clay platelets can affect the maximum filler content and that the use of larger amounts of clay platelets may result in less colloidal stability because of an increase in ionic strength of the water phase . It has also been observed that the morphology of the resulting nanocomposites was affected by the filler amount . Overall, it can safely be concluded that the synthesis of highly filled polymer–clay nanocomposites with a controlled morphology still remains a challenge.…”