Polymer nanocomposites intercalation

Sibold, N., Dufour, C., Gourbilleau, R, Metzner, M. N., Lagreve, C., Le Puart, L., Madec, P. J., and Pham, T. N. 2007. Montmorillonite for clay-polymer nanocomposites Intercalation of tailored compounds based on succinic anhydride, acid and acid salt derivatives A review. Applied Clay Science 38 130-138. 

Intercalated nanocomposites When the polymer chains intercalate into the clay gallery gaps but are unable to break down the layered structure, they are called intercalated nanocomposites (Figure 2.6a). 

Holmstrom, S.C., Patil, A.J., Butler, M. and Mann, S. (2007) Influence of polymer co-intercalation on guest release from aminopropyl-functionalized magnesium phyllosilicate mesolamellar nanocomposites. Journal of Materials Chemistry, 17, 3894—3900. 

In order to understand the thermodynamic issues associated with the nanocomposite formation, Vaia et al. have applied the mean-field statistical lattice model and found that conclusions based on the mean field theory agreed nicely with the experimental results [12,13]. The entropy loss associated with confinement of a polymer melt is not prohibited to nanocomposite formation because an entropy gain associated with the layer separation balances the entropy loss of polymer intercalation, resulting in a net entropy change near to zero. Thus, from the theoretical model, the outcome of nanocomposite formation via polymer melt intercalation depends on energetic factors, which may be determined from the surface energies of the polymer and OMLF. 

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... 

Choudhury et al. [36] in their work on hydrogenated nitrile butadiene rubber (HNBR)-nanoclay systems showed the thermodynamic aspects of nanocomposite formation using the mean-field-lattice-based description of polymer melt intercalation, which was first proposed by Vaia and Giannelis [37]. Briefly, the free... 

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). 

Rheology of various polymer layered-silicate nanocomposites - intercalated, exfoliated and end-tethered exfoliated (prepared by in-situ polymerization from reactive groups tethered to the silicate surface), have been performed in a conventional melt-state rheometer in both oscillatory and steady shear modes. These experimental studies have provided insight into the relaxation of polymer chains when confined by the layers of inorganic silicates, as well as the role of shear in orienting the layered nanocomposites. 

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. 

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. 

Nanocomposites of MMT polymer can be obtained by direct polymer melt intercalation where the polymer chains diffuse into the space between the clay galleries. This process can be carried out through a conventional meltcompounding process [6, 4]. 

M. G. Kanatzidis, C-G. Wu, H. O. Marcy, D. C. DeGroot, and C. R. Kannewurf, Conductive polymer/oxide bronze nanocomposites. Intercalated polythiophene in V2O5 xerogels, Chem. Mater., 2, 222-224 (1990). 

Bousmina, M., Study of intercalation and exfoliation processes in polymer nanocomposites. Macromolecules, 39, 4259-4263 (2006). 

The manufacturing methods for PLA nanocomposites include intercalation of polymer from solution, polymer melt intercalation and intercalation of a suitable monomer and subsequent in situ polymerization. 

Another route is polymer melt intercalation. This method, an environmentally benign one, uses all types of polymers as well as being compatible with practicing polymer industrial processes such as injection molding, being the most popular procedure to prepare nanocomposites for industrial applications. In this method, polymers, and layered hosts are annealed above the softening point of the polymer [73]. 

Botana et al. [50] have prepared polymer nanocomposites, based on a bacterial biodegradable thermoplastic polyester, PHB and two commercial montmorillonites [MMT], unmodified and modified by melt-blending technique at 165°C. PHB/Na and PHB/ C30B were characterized by differential scanning calorimetry [DSC], polarized optical microscopy [POM], X-ray diffraction [XRD], transmission electron microscopy [TEM], mechanical properties, and burning behavior. Intercalation/exfoliation observed by TEM and XRD was more pronounced for PHB30B than PHB/Na,... 

H. Sh. Xia, M. Song, Characteristic length of dynamic glass transition based on polymer/clay intercalated nanocomposites. Thermo. Acta 2005, 429, 1. 

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