Functionalization laponite clay

N. Negrete-Herrera, J.-M. Letoffe, J.-L. Putaux, L. David, E. Bourgeat-Lami, Aqueous dispersions of silane-functionalized laponite clay platelets. A first step toward the elaboration of water-based polymer/clay nanocomposites, Langmuir 2004, 20,1564-1571. 

Vaccari (1983,1999) has given a state-of-the-art account of the preparation and catalytic properties of cationic and anionic clays. Some examples of industrial importance have also been reported. Clays exhibit many desirable features, such as low cost, wide range of preparation variables, ease of set-up and wOrk-up, high selectivity, and environmental friendliness. Cationic clays are widespread in nature, whereas anionic clays are rarely found in nature, but they can be synthesized cheaply. Cationic clays are prepared from the minerals but industrial anionic clays are generally synthetic. Smectite clays exhibit both Brpnsted and Lewis acid sites on the edges of the crystals. Hammet s acidity function values are as follows Na -montmorillonite (M), -3 to t- 1.5 NH4VM -3 to 1.5 H M -8.2 to -5.6 acid activated clay less than -8.2. Laporte also has a synthetic version of cationic clays, Laponite. The acid... 

Laponite, a synthetic hectorite clay, when suspended in water, forms disclike particles with a thickness of 1 nm, a diameter of about 25 nm, and a negative surface charge density stabilizing dispersions in water. Formation of a cross-linked polymer network using a small amount of Laponite indicates that these nanoparticles act as a multifunctional cross-linker with a large effective functionality (Okay and Oppermann 2007). 

Cool et al. (80,81) performed a templated synthesis of Zr-pillared laponite using ethylenediamine in an amount exceeding the CEC of laponite. Here, the amines not only have a positive influence on the pillar distribution, but also favor the parallel orientation of the clay sheets, resulting in a more homogeneously pillared structure with increased microporosity. Thus, on laponite, the main function of the template is not to block exchange sites, but to influence the stacking of clay layers. The porosity and adsorption characteristics of the different pillared clays are summarized in Table 6. 

In Figure 10.4, smaller clay was considered in the simulation in order to take into account smaller clay types (e.g. Laponite) and to discard just entropic effects on the clay location. The structure of the clay-monomer nanodroplets as a function of the clay hydrophobicity or hydrophilicity is fairly similar to that discussed above, i.e. in most cases the clay is located at the water/monomer interface (unless a very hydrophilic, unmodified, clay is used as in the case in the... 

---