Nanocomposite exfoliated

Exfoliated nanocomposites Exfoliated nanocomposites are those where the degree of intercalation is so high that distance between the layers increases to a great extent and they no longer remain as stacked strucmre (Figure 2.6b). 

There are four main concepts involved in the synthesis and processing of nanocomposites exfoliation, orientation, compatibility and re-aggregation. 

Z. Wang and T.J. Pinnavaia, Hybrid organic-inorganic nanocomposites Exfoliation of magadiite mono-layers in an elastomeric epoxy polymer, Chem. Mater., 1998, 10 1820-1826. 

Z. Wang, T.J. Pinnavaiaand, Hybrid organic - inorganic nanocomposites exfoliation of magadiite nanolayers in an elastomeric epoxy polymer. Chemical Materials 10 (1998) 1820-1826. 

X. Fu, S. Qutubuddin (2001) Polymer-clay nanocomposites exfoliation of otgano-philic montmorillonite nanolayers in polystyrene. Polymer 42, 807. 

To prepare polymer/graphite nanocomposites, exfoliated or expanded... 

Pu X and Qutubuddin S (2001), Polymerclay nanocomposites exfoliation of organophilic montmorillonite nanolayers in polystyrene . Polymer, 42, 807. 

Maiti and Bhowmick reported exciting results that a polar matrix like fluoroelastomer (Viton B-50) was able to exfoliate unmodified clay (Cloisite NA ) as well as the modified one (Cloisite 20A) [93]. They studied morphology, mechanical, dynamic mechanical and swelling properties of fluoroelastomer nanocomposites. The unmodified-clay-filled systems showed better properties than the modified ones (Table 2.3). 

When a solvent diffuses across a neat polymer, it must travel the thickness of the sample (do). When the same solvent diffuses through a nanocomposite film with nanoclays, its path length is increased by the distance it must travel around each clay layer it strikes. According to Lan et al. [99] the path length of a gas molecule diffusing through an exfoliated nanocomposite is... 

Novel room-temperature-vulcanized silicone mbber-organo-MMT nanocomposites were prepared by a solution intercalation process by Wang et al. [104]. A new strategy was developed by Ma et al. [105] to prepare disorderly exfoliated nanocomposites, in which a soft siloxane surfactant with a weight-average molecular weight of 1900 was adopted to modify the clay. 

This is a highly polar polymer and crystalline due to the presence of amide linkages. To achieve effective intercalation and exfoliation, the nanoclay has to be modified with some functional polar group. Most commonly, amino acid treatment is done for the nanoclays. Nanocomposites have been prepared using in situ polymerization [85] and melt-intercalation methods [113-117]. Crystallization behavior [118-122], mechanical [123,124], thermal, and barrier properties, and kinetic study [125,126] have been carried out. Nylon-based nanocomposites are now being produced commercially. 

FIG. 10 Compressive (a) yield strength and (b) moduli for the pristine epoxy polymer and the exfoliated epoxy-clay nanocomposites prepared from three different kinds of organomontmorillonites. (From Ref. 40.)... 

Polyimide-clay nanocomposites constitute another example of the synthesis of nanocomposite from polymer solution [70-76]. Polyimide-clay nanocomposite films were produced via polymerization of 4,4 -diaminodiphenyl ether and pyromellitic dianhydride in dimethylacetamide (DMAC) solvent, followed by mixing of the poly(amic acid) solution with organoclay dispersed in DMAC. Synthetic mica and MMT produced primarily exfoliated nanocomposites, while saponite and hectorite led to only monolayer intercalation in the clay galleries [71]. Dramatic improvements in barrier properties, thermal stability, and modulus were observed for these nanocomposites. Polyimide-clay nanocomposites containing only a small fraction of clay exhibited a several-fold reduction in the... 

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