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The definition of nanocomposite material has broadened significantly to encompass a large variety of systems such as one-dimensional, two-dimensional, three-dimensional and amorphous materials, made of distinctly dissimilar components and mixed at the nanometer scale.
Classification of Nanocomposites
The general class of nanocomposite organic/inorganic materials is a fast growing area of research. Significant effort is focused on the ability to obtain control of the nanoscale structures via innovative synthetic approaches. The properties of nanocomposite materials depend not only on the properties of their individual parents, but also on their morphology and interfacial characteristics.
The Emergence of New Materials with Novel Properties
This rapidly expanding field is generating many exciting new materials with novel properties. The latter can be derived by combining properties from the parent constituents into a single material. There is also the possibility of new properties which are unknown in the parent constituent materials.
The Different Types of Framework Systems for Inorganic Components
The inorganic components can be three-dimensional framework systems, such as zeolites; two-dimensional layered materials, such as clays, metal oxides, metal phosphates, chalcogenides; and even one-dimensional and zero-dimensional materials, such as (Mo3Se3-)n, chains and clusters.
Industry Applications for Nanocomposites
Experimental work has generally shown that virtually all types and classes of nanocomposite materials lead to new and improved properties, when compared to their macrocomposite counterparts. Therefore, nanocomposites promise new applications in many fields such as mechanically-reinforced lightweight components, non-linear optics, battery cathodes and ionics, nanowires, sensors and other systems.
Organic/Inorganic Nanocomposites and Lamellar Nanocomposites
The general class of organic/inorganic nanocomposites may also be of relevance to issues of bio-ceramics and biomineralization, in which in-situ growth and polymerization of biopolymer and inorganic matrix is occurring. Finally, lamellar nanocomposites represent an extreme case of a composite in which interface interactions between the two phases are maximized.
Benefits of Studying the Interactions of Nanocomposites
Since the remarkable properties of conventional composites are mainly due to interface interactions, the materials dealt with here could provide good model systems in which such interactions can be studied in detail using conventional bulk sample (as opposed to surface) techniques. By judiciously engineering the polymer-host interactions, nanocomposites may be produced with a broad range of properties.
Inorganic Layered Materials - Properties and Uses
Inorganic layered materials exist in great variety. They possess well defined, ordered intralamellar space potentially accessible by foreign species. This ability enables them to act as matrices or hosts for polymers, yielding interesting hybrid nanocomposite materials.
The Two Types of Lamellar Nanocomposites: Intercalated Nanocomposites and Exfoliated Nanocomposites
Lamellar nanocomposites can be divided into two distinct classes, intercalated and exfoliated. In the former, the polymer chains alternate with the inorganic layers in a fixed compositional ratio and have a well defined number of polymer layers in the intralamellar space. In exfoliated nanocomposites, the number of polymer chains between the layers is almost continuously variable and the layers stand >100 Å apart. The intercalated nanocomposites are also more compound-like because of the fixed polymer/layer ratio, and they are interesting for their electronic and charge transport properties. On the other hand, exfoliated nanocomposites are more interesting for their superior mechanical properties.
Studying the Lamellar Class of Intercalated Organic/Inorganic Nanocomposites
Our work focuses on the lamellar class of intercalated organic/inorganic nanocomposites and namely those systems that exhibit electronic properties in at least one of the components. This subclass of nanocomposites offers the possibility of obtaining well ordered systems some of which may lead to unusual electrical and mechanical properties. Selected members of this class may be amenable to direct structural characterization by standard crystallographic methods. An important issue in this area is the few structural details that are available, therefore, any system which can be subjected to such analysis is of interest.
Combining the Diverse Properties of Nanocomposites and Building Heterostructures of Inorganic Layers
Nanocomposites also offer the possibility to combine diverse properties which are impossible within a single material, e.g. flexible mechanical properties and superconducting properties. This work is now in its infancy, and we propose to carry out extensive investigations in the next funding period. Another exciting aspect is the possibility of creating heterostructures composed of different kinds of inorganic layers, which could lead to new multifuntional materials.
Novel Nanocomposites Designed by the Department of Chemistry at Michigan State University
In the past, we have focused our efforts on creating such materials with conjugated and saturated organic macromolecules. We have developed several general synthetic routes for inserting polymer chains into host structures, and have designed many novel nanocomposites.
These include:
• In-situ intercalative polymerization (ISIP) of a monomer using the host itself as the oxidant. The rationale behind intercalative polymerization is that host matrices with high electron affinity can oxidatively polymerize appropriate monomers in their interior.
• Monomer intercalation followed by topotactic intralamellar solid state polymerization. This route creates conjugated polymers inside non-oxidizing hosts.
• Direct precipitative encapsulation of polymer chains by colloidally dispersed single layers of a host. This approach gives access to a large variety of nanocomposites with many kinds of polymers and hosts. |