Intercalated polymer nanocomposites

Intercalated polymer nanocomposites are those in which the polymer chains are incorporated into the layers or tubes of the nanomaterial in a regular fashion, regardless of the nanomaterial to polymer ratio. The extended polymer chain is inserted between the layers of nanomaterial, resulting in a well ordered multi-layer with alternating polymer chain and layers of nanomaterial at a repeating distance of a few nanometres (Fig. 11.1a). 

Nevertheless, XRD is a useful tool to study the d-spacing of ordered intercalated polymer nanocomposites, it might not be sufficient for exfoliated nanocomposites with no peak. It is generally accepted that transmission electron microscopy (TEM) is the best direct method to demonstrate the dispersion of nanofillers in a polymer matrix. It has been widely used to investigate the dispersion of day in a PET matrix. Eigure 5.4 shows the TEM study of PET/MMT composites [14]. It can be observed that the dispersion of clay in the composites varies due to different processing procedures. It can be either labeled as nanocomposites or conventional... 

Mohapatra SR, Thakur AK, Choudhary RNP (2009) Effect of nanoscopic confinement on improvement in ion conduction and stability properties of an intercalated polymer nanocomposite electrolyte for energy storage applications. J Power Sources 191 601-613 Napolitano S, Cangialosi D (2013) Interfacial free volume and vitrification rednctiai in Tg in proximity of an adsorbing interface explained by the free volume holes diffusitm model. Macromolecules 46 8051-8053... 

XRD was used to investigate the spacings of silicate layers of montmorillonite (from 1.9 to 4nm) in PP/montmorillonite (MMT) nanocomposites prepared by in situ graft-intercalation in the presence of acrylamide [331]. Similarly, XRD and TEM were used to study the dispersibility of PP/MMT nanocomposites prepared by melt intercalation using organo-montmorillonite and conventional twin screw extrusion [332]. Various delaminated and intercalated polymer (PA6, PA 12, PS,... 

Since the possibility of direct melt intercalation was first demonstrated [11], melt intercalation has become a method of preparation of the intercalated polymer/ layered silicate nanocomposites (PLSNCs). This process involves annealing, statically or under shear, a mixture of the polymer and organically modified layered fillers (OMLFs) above the softening point of the polymer. During annealing, the polymer chains diffused from the bulk polymer melt into the nano-galleries between the layered fillers. 

An additional route consists of using the reconstruction ability of some LDH materials after a moderate thermal treatment. This is a pecuharity of LDH systems called the memory effect the LDH lamellar framework is reconstructed in the presence of the polymer with concomitant intercalation. Finally, a post-synthesis hydrothermal treatment can be applied in all cases, which may improve the inter- and intralamellar organization of the LDH/polymer nanocomposites. 

In situ polymerization is generally a highly suitable method for the ob-tention of LDH/polymer nanocomposites. Various monomers can be intercalated and polymerized within the interlamellar space of LDH and this spatial confinement is believed to increase the degree of polymerization. Yet, the process is limited by two factors [43] ... 

Organic molecules such as aniline, pyrrole and 2,2 -bithiophene have been intercalated and polymerized within the galleries of clay minerals, FeOCl, V2O5 gel and other layered hosts to yield multilayered inorganic/organic polymer nanocomposites... 

R. A. Vaia, B. B. Sauer, O. K. Tse, and E. P. Giannelis, Relaxations of confined chains in polymer nanocomposites Glass transition properties of poly(ethylene oxide) intercalated in montmorillonite, J. Polym. Sci. B Polym. Phys. 35(1), 59-67 (1997). 

Three areas of the intercalation chemistry of clays have received very detailed study and will be described further (a) intercalation of organic cations and neutral organic molecules (b) pillaring reactions and (c) clay polymer nanocomposites. 

Vaia, R.A. Jandt, K.D. Kramer, E.J. Giannelis, E.P. Microstructural evolution of melt intercalated polymer-organically modified layered silicates nanocomposites. Chem. Mater. 1996, 8, 2628-2635. 

The most commonly studied polymer nanocomposites are clay-based nanocomposites, mainly with montmorillonite (MMt) as layered silicate filler (Scheme 15.12). Upon incorporation of organomodihed clays (organoclays) into a polymer matrix, two nanomorphologies (Scheme 15.13) can be obtained, either intercalation of the polymer chain in between the clay platelets keeping the stacking of the sheets, or exfoliation of the clay platelets with a disordered dispersion of the inorganic sheets in the polymer. 

Conducting polymers such as PANl- or PPY-intercalated clay-type minerals are another type of ER particle material. Kim et al. synthesized PPY-intercalated montmorillonite nanocomposites through inverted emulsion pathway polymerization, and characterized its ER effect under an electric field [38]. The nanocomposites showed not only a typical ER behavior under electric fields but also the existence of a critical electrical field when the yield stress was plotted as a function of the electric field. 

Intercalation refers to the inclusion of molecules between the layers. Exfoliation refers to the separation of the layers. In other words, intercalated polymer chains are sandwiched in between clay layers. In exfoliated nanocomposites the individual layers are separated, and somewhat uniformly dispersed in the polymeric matrix. This class of materials has been widely investigated because of their unique properties. The efficiency of PPV-related electroluminescent devices is summarized in Table 3.5. 

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