Latexes miniemulsion clay

Bon, Keddy, and coworkers [109] demonstrated that soft armored polymer latex made via Pickering miniemulsion polymerization [i.e., poly(lauryl acrylate) armored with Laponite clay discs] could be used as a nanocomposite additive in standard poly(butyl acrylate-co-acrylic acid) waterborne pressure-sensitive adhesives (PSAs), leading to marked mechanical property enhancements (see Fig. 13). 

Cauvin S, Colver PJ, Bon SAF (2005) Pickering stabriized miniemulsion polymerization preparation of clay armored latexes. Macromolecules 38(19) 7887-7889... 

Inverted raspberry-like morphologies (the mineral particles being located at the surface of the latex spheres) have also been discussed in Sections 4.4.2.2 and 4.4.2.4 about colloidal silica and layered silicates, respectively. These are mainly a consequence of the surfactant-like behavior of the inorganic particles in specific situations. This was clearly illustrated in a recent report by Landfester, who showed that silica or clays can be used as pickering stabilizers of miniemulsion jxjlymer-izations, resulting therefore in the formation of armored latexes, the surface of which was recovered by the small inorganic particles [99,131]. 

B. zu Putlitz, K. Landfester, H. Fischer, M. Antonietti, The generation of armored latexes and hollow inorganic shells made of clay sheets hy templating cationic miniemulsions and latexes, Adv. Mater 2001, 13, 500-503. 

Hatami L, Haddadi-Asl V, Roghani-Mamaqani H, Ahmadian-Alam L, Salami-Kalajahi M (2011) Synthesis and characterization of poly(styrene-co-butyl acrylate)/clay nanocomposite latexes in miniemulsion by AGET ATRP. Polym Comp 32 967-975... 

Many of the papers described emulsion or miniemulsion polymerization in the presence of unmodified or modified clays (often MMT). The modifieation can be surface modification, edge modification or both. lanchis et al. claimed that they obtained both clay platelets (silylated MMT) inside the latex partieles and on the surface of latex particles. Although the elay was not easily visible in the TEM pictures presented, they indirectly inferred the presence of MMT platelets inside the latex particles by looking at the shape of the latex particles. Snowman morphologies were associated with the encapsulated clay. Recently, reversible addition-fragmentation chain transfer (RAFT)-mediated... 

Waterborne acrylic-clay nanocomposite PSAs have been synthesized by suspension polymerization, emulsion polymerization and Pickering miniemulsion polymerization of a soft acrylate monomer in the presence of clay, which was followed by blending the polymer-clay nanocomposite particles with a standard acrylate latex for application as a waterborne PSA. ... 

One of the main goals of academic research is the encapsulation of organically modified clay in miniemulsion droplets and, upon polymerization, in latex particles. In order to achieve this, it is necessary to have only droplet nucleation and to avoid secondary nucleation. There are examples in the literature of encapsulation of inorganic particles via miniemulsion polymerization, but there is no clear evidence of successful encapsulation of clay or only under limited conditions (low solids content, high surfactant loading) in papers devoted to miniemulsion polymerization of waterborne polymer-clay nanocomposites. 

Figure 10.8 TEM images of (left) the miniemulsion latex of PS-PCDBAB-3.6% MMT nanocomposite with 11 % hydrophobe and (right) PS-PCDBAB-3.6% MMX clay nanocomposite film. Reprinted from reference 74 with permission from Wiley.

In the case of polymer-clay latexes prepared by miniemulsion polymerization, it is very problematic to obtain stable latexes at a reasonable solids content. Most of the studies presented up to now had very low (<5% " ), low ( 10% ) or relatively low ( 20% °) solids contents. 

Mechanical Properties of the Latex Films. Figure 13.18 shows a noteworthy effect of the addition of Laponite on the mechanical properties of the nanocomposite film. A remarkable increase in the storage modulus at the rubbery plateau was observed with the addition of only 5 wt% Laponite. This improvement of the mechanical properties of the poly(styrene-co-butyl acry-late)-Laponite film was expected, considering the good dispersion of the clay platelets inside the polymeric matrix and the armored morphology of the hybrid particles. It is worth remembering here that similar results were reported by Ruggerone and co-workers" and Faucheu et al. for PS-Laponite films obtained from latexes prepared by emulsion and miniemulsion polymerization, respectively (see Sections 13.3.2.1 and 13.3.2.2). 

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