Inorganic network systems

In the present work, we have reviewed results on molecular glass formers, but it is not clear to what extent the observed relaxation features are also found in more complex systems, such as polymers and inorganic network glasses. Susceptibility spectra covering, say, more than 10 decades in frequency are still rare for the case of more complex systems. For example, how does the manifestation of the dynamic crossover change when going from a molecular liquid to a polymer ... 

To meet the challenges of new material requirements, scientists must strive constantly to develop new systems. One recent approach has been to prepare inorganic-organic hybrid materials by using the sol-gel method common to ceramists. This technique allows a considerable range of chemistry to be used and may lead to the development of a whole array of systems that have potential applications (structural, optical, etc.). This chapter provides an overview of the general status of this approach, with emphasis on the work that comes from our laboratory. The chemistry discussed in this chapter involves the use of silicon-containing species in the preparation of polymeric network systems. 

Owing to the computational simplicity of force-field calculations, very large systems can be examined in short periods of time. These are the methods of choice for studying the structure of synthetic polymers, proteins, nucleic acids, and inorganic networks such as zeolites. Force-fields are also used to provide the energies in molecular dynamics calculations, in which the time evolution of structures can be examined. 

Fig. 1. Hybrid organic-inorganic polymer systems can be devised for all structural paradigms of polymer chemistry including (a) homopolymer, (b) block copolymer, (c) copolymer, (d) graft copolymer, and (e) interpenetrating polymer networks, including, shown as geometrical abstractions, (f) true and (g) semi-interpenetrating versions, where crosslinks are depicted as junctions of horizontal and vertical lines.

Fig. 11. Automotive finishes such as that on the Honda Civic have depth, luster and environmental resistance that is the result of a complex mixture of hybrid organic-inorganic materials cured into mixed graft interpenetrating polymer network systems.

Only newer technologies can improve on the best we have. We would therefore like to show how improvements can be achieved in coatings by integrating an Si-O-Si (inorganic) network into the coating system. 

FIGURE 5.2.3 Classification of soft shape-memory materials from the viewpoint of nanoaivhitectonics. (a-c) Structures and (d) molecular mechanism, (a) Chemically cross-linked polymer network, (b) supramolecular network with clay nanosheets [29], and (c) inorganic/polymer composite network system, and their shape-memory profiles [30]. (d) The nanoscale molecular mechanism for one-way and two-way SME of a cross-linked semicrystalline polymer system. 

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