Polymer intercalations

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. 

Ternary blends One way to overcome these limitations is the use of ternary polymer blends. This approach makes use of the principle described in section 1.1.2, in which one of the polymer components wets the interface of the other two. By providing a pre-pattemed substrate with surface regions, to which these two polymer segregate, it is possible to form structures in the intercalated polymer with dimensions that are not directly connected to the substrate pattern. 

Moreover the evolution of the XRD during annealing can be modeled to determine the apparent diffusivity, D, of the polymers within the silicate gallery. Namely, the ratio of the amount of intercalated polymer at time t, Q(t), to that at equilibrium Q(°°) is [30] ... 

The presence of cooperative motion of chain segments present in intercalated polymer chains can be examined using various analytical techniques such as Differential Scanning Calorimetry (DSC), thermally stimulated current (TSC) and dielectric spectroscopy. DSC measurements on an intercalated PEO, (Mw= 100,000)/montmorillonite hybrid (20 wt. % polymer), indicated the absence of... 

Fig. 16. DSC measurements of a polystyrene/C18FH intercalated hybrid. For comparison DSC traces for the neat polymer and for a physical mixture of the polymer and the organically modified silicate are also shown. There is an absence of any thermal transition for the intercalated polymer around the bulk Tg [45].

The influence of neutral polymer polyethylene glycol and two surfactants with different charge, anionic sodium dodecylsulfate and cationic cetyltrimethylammonium bromide, on the intercalation of pre-formed Au nanoparticles into a clay matrix under ultrasonic treatment has been investigated. The polymer (surfactant) addition has been used to modify the active surface area of NaLmontmorillonite and to change the interlamellar space between the clay layers. Then, intercalated polymer (surfactant) in clay composites has been successfully replaced by Au nanoparticles under sonication. 

The intercalation of nano-gold into clay layers comprised two steps. The first step was the intercalation of the polymer (surfactant) into clay matrix for increasing the interlamellar space between the clay layers. The second step was the replacement of the intercalated polymer (surfactant) by Au nanoparticles by adding different amounts of nanoparticles to the polymer (surfactant)/clay composite. Both steps were performed by applying ultrasonic irradiation. The solution was sonicated at 20 kHz, 500 W. The intercalation progress was monitored as a function of time. The precipitated nano-Au/intercalated product was separated by centrifugation, washed with water and dried under vacuum overnight. After that samples were calcined in air at 800 °C for 4 h. 

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. 

Recently, Vaia et al. [8] reported a new process for direct polymer intercalation based on a predominantly enthalpic mechanism. By maximization of the number of polymer host interactions, the unfavorable loss of conformational entropy associated with intercalation of the polymer can be overcome leading to new intercalated nanostructures. They also reported that this type of intercalated polymer chain adopted a collapsed, two-dimensional conformation and did not reveal the characteristic bulk glass transition. This behavior was qualitatively different from that exhibited by the bulk polymer and was attributed to the confinement of the polymer chains between the host s layers. These types of materials have important implications not only in the synthesis and property areas, where ultrathin polymer films confined between adsorbed surfaces are involved. These include polymer filler interactions in polymer composites, polymer adhesives, lubricants, and interfacial agents between immiscible phases. 

Using a similar synthetic methodology, other water soluble polymers, such as poly(vinylpyrrolidinone) (PVP), polyfpropylene glycol) (PPG), and methyl cellulose (MCel) were intercalated into V20s.nH20 xerogels [41]. The ratio of intercalated polymer to the layered host could be synthetically manipulated. Similarly to PEO, PVP, PPG, and MCel could also function as solid electrolytes when complexed with lithium salts, and hence their relevance in lithium battery applications. The intercalation of PEO into V20snH20 was also reported by Ruiz-Hitzky et al. [42]. 

VOPO4.2H2O is capable of undergoing in situ intercalation/polymerization with molecules such as aniline [50, 51], substituted anilines [52,53,54], and pyrroles [55]. Evidence of intercalation was obtained from powder X-ray diffraction. As an example, the powder pattern of poly(A-methylaniline) (PMA) intercalated into VOPO4 is illustrated in Figure 6.11. The identity of the intercalated polymer was confirmed by Fourier-transform infrared studies. 

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. 

Hou. S.S. Beyer. F.L. Schmidt-Rohr, K. High-sensitivity multinuclear NMR spectroscopy of a smectite clay and of clay-intercalated polymer. Solid State Nucl. Magn. Reson. 2002. 22. 110-127. 

Vaia RA, Jant KD, Kramer EJ, Giaimelis EP.(1996). Microstructural evaluation of melt-intercalated polymer-organically modified layered silicate nanocomposites. Chem Mater. 8 2628-35. 

Sen, S. and CayU, G. (2010) Synthesis of bio-based polymeric nanocomposites from acrylated epoxidized soybean oil and montmorillonite clay in the presence of a bio-based intercalant. Polymer International, 59(8), 1122-1129. 

LOW-DIMENSIONAL ELECTRICALLY CONDUCTIVE SYSTEMS INTERCALATED POLYMERS IN V2O5 XEROGELS... 

Mallakpour S, Dinar M. Insertion of novel optically active poly(amide-imide) chains containing pyromellitoyl-bis-l-phenylalanine linkages into the nanolayered silicates modified with 1-tyrosine through solution intercalation. Polymer 2011 52(12) 2514-23. 

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). 

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