Nanocomposites of organo-montmorillonite/polystyrene latex particles via free radical miniemulsion polymerization

TL;DR

This paper describes a new method to encapsulate organo-montmorillonite platelets in polystyrene using miniemulsion polymerization, creating stable nanocomposites with improved thermal properties.

Contribution

A novel approach to encapsulate high-aspect-ratio inorganic particles in polymers, avoiding armored or dumbbell-like morphologies.

Findings

XRD and TEM confirmed exfoliated MMT structures within spherical polystyrene particles.

The nanocomposites showed enhanced thermal stability compared to pure polystyrene.

The method allows encapsulation of high-aspect-ratio nanofillers for controlled-release applications.

Abstract

Encapsulation of high-aspect-ratio inorganic particles by polymeric materials is still a challenge; armored or dumbbell-like morphologies were frequently the outcome. In this paper, through miniemulsion polymerization, organo-montmorillonite (MMT) platelets have been successfully encapsulated by polystyrene (PS). First, MMT was hydrophobized by cation exchange with a polymerizable interlayer spacer (N-allyl-N,N-dimethyloctadecan-1-aminium bromide), which not only widened the interplanar spacing but also facilitated monomer intercalation into the MMT nanogalleries and provided a covalent anchor with PS chains. Then, the swelled modified MMT in the monomer phase was combined with a surfactant, costabilizer, and initiator to obtain stable nanocomposite latexes. Analytical techniques, including FTIR, XRD, SEM, TEM, and TGA, provided comprehensive insights into the structural and thermal properties of these nanocomposites. XRD analyses unveiled an exfoliated structure. Furthermore, the TEM micrographs showed the formation of stable spherical particles with diameters ranging from 250 to 465 nm containing encapsulated MMT. These nanocomposites exhibited significant improvement in thermal stability—decomposing at elevated temperatures compared to virgin PS. This work opens new avenues for encapsulating other high-aspect-ratio nanofillers in a diverse array of polymer types, leading to the synthesis of innovative materials with enhanced properties for broader practical applications. Furthermore, it can be used for controlled-release applications, particularly in drug delivery and agriculture.

Hydrophobization of MMT with a reactive ADM18 molecule and its encapsulation into polystyrene latex particles via miniemulsion polymerization.

Figures