Intercalated and Exfoliated Nanocomposites

In the area of polymer technology prior to the anergence of nanotechnology, nanoscale dimensions were recognized in some areas  

Phase-separated polymer blends often feature nanoscale phase dimensions  

Block copolymer domain morphology is often at the nanoscopic level  

Asymmetric membranes often have nanoscale void structure  

List of Experiments to Eorm Materials with Predetermined Morphology 

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Su, S., Jiang, D. D., and Wilkie, C. A. Novel polymerically-modified clays permit the preparation of intercalated and exfoliated nanocomposites of styrene and its copolymers by melt blending, Polym. Degrad. Stab. (2004), 83, 333-346. 

Both intercalated and exfoliated nanocomposites, containing 3-5% of nanoparticles (w/w), reportedly show better or comparable flame resistance compared with plastics filled up to 30-50% with traditional flame retardants. Another way to increase flame retardancy is to combine ATH or magnesium hydroxide with organo-clays. It was reported that organoclays and some classical flame retardants, such as brominated compounds, showed a synergism between them [13]. 

Figure 15.2 Schematic representation of intercalated and exfoliated nanocomposite from layered silicate clay filler and polymer.

Incorporation of clay or layered silicates to polymer matrix provides three different stmctures conventional composites, intercalated and exfoliated nanocomposites and these are shown in Fig. 1. It is interdependent on the clay concentration the degree of clay layer separation and distribution in the composites [14]. In conventional composites the particles exist as aggregates with no insertion of polymer matrix. 

Montmorillonite (MMT), a smectite clay, is probably the most extensively studied nanomaterial in terms of mechanical, thermal, fire retardant or crystallization behavior of polylactide, especially when these nanoparticles are organically modified allowing the achievement of intercalated and exfoliated nanocomposites.These nanocomposites show enhanced properties as compared to microcomposites and pristine polymer. However, biodegradation and hydrolytic degradation of PLA in the presence of nanoclays has been investigated to a small extent. 

Fig. 4 Early work in inorganic nanoclay-polymer composites helped define terminology that has persisted in the field. This scheme demonstrates the differences between phase separated, intercalated, and exfoliated nanocomposites, noticeably when the filler exists in thin platelet or rod geometries. Reprinted from Alexandre and Dubois [46], Copyright 2000, with permission from...

What are the differences in morphology of immiscible, intercalated and exfoliated nanocomposites ... 

Based on the interaction between the polymer matrix and layered silicate polymer layered silicate nanocomposites are classified into intercalated and exfoliated nanocomposites [56-58]. Figure 7 represents the intercalated and exfoliated nanocomposites along with the conventionally filled microcomposite. 

The dispersion of nano-sized fillers into polymer matrix creates a tortuous path for the diffusant in comparison to neat polymer having straight diffusive path perpendicular to the film (Figure 3). In case of intercalated and exfoliated nanocomposites, path travelled by diffusant molecule would be greater than that of aggregate micro composite. 

Both intercalated and exfoliated nanocomposites are degraded at higher temperatures as compared to PCL and PCL/clay microcomposites. Furthermore, the resistance to thermal degradation is improved when the... 

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