Polymer-clay network structure

The formation of three-dimensional polymer networks during the synthesis process has long been an important subject in polymer chemistry and physics [63-66]. The mechanism of formation of the organic (polymer)-inorganic (clay) network structure of NC gels was elucidated on the basis of changes in viscosity, optical transparency, XRD, and mechanical properties [39]. 

Soft nanohybrid materials with novel organic-inorganic network structures, such as nanohydrogels, soft nanocomposites (solid), and their derivatives are described in the chapter Soft Nanohybrid Materials Consisting of Polymer-Clay Networks. Synthesis of polymer hybrids based on metal-oxide nanoparticles are discussed in Fabrication of Metal Oxide-Polymer Hybrid Nanocomposites. Some properties and applications of these hybrid nanocomposites are also discussed in this chapter. 

Figure 11 Schematic representation of the organic (polymer)/inorganic (clay) network structure of NC-gels. D-k is the interparticle distance of the exfoliated clay platelets./, g, and represent the cross-linked chains, grafted chains, and looped chains, respectively. The surface of a clay platelet is surrounded by a polymer layer with a thickness of 1 nm. Only a small number of polymer chains are depicted for simplicity. Reprinted with permission from Haraguchi, K. Famworth, R. Ohbayashi, A. Takehisa, T. Macromolecules2htt3,36,5732-5741. Copyright 2003 American Chemical Society.

Most of the previous studies on flame retardation of polymer nanocomposites are focused on the relationship between macroscopic morphologies of chars and the flammability properties. Fang et al. studied the relationship between evolution of the microstructure, viscoelasticity and graphitization degree of chars and the flammability of polymers during combustion (68). The flame retar-dancy of ABS/clay /MWNTs nanocomposites was strongly affected by the formation of a network structure. Flammability properties... 

The characterization of the physical and chemical changes that occur in montmorillonite/PDMS nanocomposite elastomers as they are thermally aged is reported. Broadband Dielectric Spectroscopy (BDS) was used to track changes in the physical interaction between the polymer and clay associated with increases in non-oxidative thermal stability (as determined by TGA). The evolution of volatile siloxane species from the elastomers was characterized with Thermal Volatilization Analysis (TVA). Results suggest that the improved thermal stability and the increases in polymer/clay association are a result of significant re-structuring of the polymer network. 

Coagulation structures are formed by pigments and fillers of paints, varnishes and polymers. Spacial networks that form during coagulation of clay suspensions by electrolytes represent a characteristic example of thixotropic systems. Due to their ability to undergo structuring in aqueous media, finely dispersed bentonite and montmorillonite clays are widely used as main components of drilling liquids (see Chapter IX, 3) [32]. 

FIGURE 5.2.3 Classification of soft shape-memory materials from the viewpoint of nanoaivhitectonics. (a-c) Structures and (d) molecular mechanism, (a) Chemically cross-linked polymer network, (b) supramolecular network with clay nanosheets [29], and (c) inorganic/polymer composite network system, and their shape-memory profiles [30]. (d) The nanoscale molecular mechanism for one-way and two-way SME of a cross-linked semicrystalline polymer system. 

Fig. 6 (a) Structural model showing organic (polymer)-inorganic (clay) networks in the NC gel. Dio is the interparticle distance of exfoliated clay sheets. /, gi, and g2 represoit crosslinked chain, grafted chain, and looped chain, respectively. In the model, only a small number of polymer chains are depicted for simplicity [19, 20, 54]. (b) Decorated clay platelet sandwiched by polymer layer [52]. (a) Reprinted from Haraguchi and Li [54], Copyright 2009, with permission of Wiley... 

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