Organic/Inorganic Molecular Hybrid Materials From Cubic Silsesquioxanes
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one component has at least one dimension that is < 100 nm. Thus, nanocomposites will be strongly influenced by extensive interfacial interactions between the components, which is one reason that the rule of mixtures fails in predicting properties. Indeed, at the finest scales, interfacial interactions may be the sole source of properties. At this point the interface can be considered to be a material phase in its own right. The term "interphase," has already been used in composite materials studies [1-3]. Given that interfacial interactions are likely to play an exceptional role in nanocomposite materials properties, especially for organic/inorganic materials; the following questions arise:
"*How does one synthesize materials with well defined interphases? "*How does one characterize the architecture of the interphase? "*How does one characterize interphase properties? If these questions can be answered, then in principle, it should be possible to develop synthesisstructure-property relationships that will guide the design and synthesis of new nanocomposite materials, new interphases and control the global properties of these materials. The long term goal of the work presented here is to provide answers to these questions. We have developed a specific strategy that provides answers to these questions in a well defined area of hybrid nanocomposites, but given the breadth of the field, we do not presume to be able provide answers that work for all types of materials. In the following section, we briefly describe the types of nanocomposites that can be made. We then delineate the types of architectures we are exploring and in the following section, we present our results.
Mat. Res. Soc. Symp. Proc. Vol. 576 ©1999 Materials Research Society
BACKGROUND Given that our goal is to develop a detailed understanding of interfaces in organic/inorganic nanocomposites, it is instructive to briefly discuss the various types of nanocomposite architectures, without being completely inclusive, and then to describe the types that we are exploring and our rationale for doing so. In general, one can describe architectures wherein the two (or more) components in the nanocomposite form either continuous or discontinuous phases. Figure 1 depicts a simple example of a discontinuous, inor ihase in a continus oranic hase:
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Figure 1. Illustration of a segregated inorganic phase in a continuous organic phase. Similar systems with an organic minority phase have been made and described in detail [4-7]. In Figure 1, one phase is discontinuous and the other is continuous. Hybrid nanocomposites can also be made that have two continuous and contiguous phases. Two architectures, illustrative of block copolymer microstructures, can also be used to describe mutually continuous segregated phases, as illustrated below [81:
Figure 2 [8]. Gyroid Segregated Phases
Cubic Segregated Phases
Still other types of discontinuous and continuous systems can be described, including lamellar materials as suggested by Figure 3 for a p
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