Types of Inorganic Polymers

Specifically, the greatest emphasis in the following chapters is placed on polyphosphazenes (1.9), polysiloxanes (1.10), and polysilanes (1.11). Chapters 6 and 7 introduce a wide variety of other polymers that contain elements such as phosphorus, germanium, sulfur, boron, aluminum, and tin, and a variety of transition metals. These polymers are expected to provide the basis for many of the new advances of the future. Chapter 8 

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As already stressed in the Introduction to this article, the use of organic plastics as biomaterials is expected to evolve in a natural way towards the utilization of increasingly higher quantities of inorganic polymers, because of the limitations inherently present in the first class of materials which seem to be absent or reduced in the second type of macromolecules. 

The last of these is perhaps the best criterion for metallic characteristics. Most other types of inorganic substance are effectively insulators, or semiconductors whose conductivity increases with temperature. Semiconductors constitute a borderline area some lie between metals and three-dimensional polymers (e.g. GaAs, isoelectronic and isostructural with elemental germanium), while others have structures which could be described as ionic (e.g. PbS, which has the NaCl structure). 

Polysilanes have proved to be an intriguing class of inorganic polymers with many versatile applications in ceramics, photoelectronics, photoresistors, and nonlinear optics.8,9 The unusual optoelectronic properties of polysilanes are attributed to sigma-conjugation of the silicon atoms in the polymer backbone chain, depending on the molecular weight, conformation, and substituents of the polymer.10a Wurtz-type... 

The first truly synthetic resin was developed by Baekeland in 1911 (phenol-formaldehyde). This was soon followed by a petroleum-derived product called coumarone-indene, which did indeed have the properties of a resin. The first synthetic elastomer was polychloroprene (1931) originated by Nieuwland and later called neoprene. Since then many new types of synthetic polymers have been synthesized, perhaps the most sophisticated of which are nylon and its congeners (polyamides, by Carothers), and the inorganic silicone group (Kipping). Other important types are alkyds, acrylics, aminoplasts, polyvinyl halides, polyester, epoxies, and polyolefins. 

As the adduced above data have shown, the polymer nanocomposites with three main types of inorganic nanofiller and also polymer-polymeric nanocomposites melt viscosity caimot be described adequately within the fiamework of models, developed for the description of microcomposites melt viscosity. This task can be solved successfully within the framework of the fractal model of viscous liquid flow, if in it the used nanofiller special feature is taken into account correctly. Let us note that unlike microcomposites nanofiller cotents enhancement does not result in melt viscosity increase, but, on the contrary, reduces it. It is obvious, that this aspect is very important from the practical point of view. 

Thus, particles with a very narrow distribution were observed - in the case of a second generation dendrimer, nanoparticles with a monodisperse nucleus of 2.4 0.2 nm. It is important that not only individual dendrimers can be used for metallopolymer preparation, but also their dispersed mixtures with polymer matrices, which form new types of polymer-inorganic nanomaterials. For example, the highest poly(amidoamide) generations in water were put in swollen polymeric patterns of poly(2-hydroxyethylmethacrylate) Cu, Au or ions of a complex bound to dendrimer [90] were added to such a composition. Reduction of the metal ions resulted in new types of inorganic hybrid materials. 

R 514 R. Micura and C. Hoebartner, On Secondary Structure Rearrangements and Equilibria of Small RNAs , ChemBioChem, 2003,4,984 R 515 V. N. Mitkin, Types of Inorganic Fluorocarbon Polymer Materials and Structure-Property Correlation Problems , J. Struct. Chem., 2003,44,82 R 516 S. Miyahara and K. Ueda, Theory of the Orthogonal Dimer Heisenberg... 

An alternative approach to immobilize organic compounds such as MPC to metal substrates is the use of mussel-inspired chemistry. Mussels can rapidly and permanently adhere to all types of inorganic and organic surfaces in aqueous environments. Such adhesive properties rely on repeats of the 3,4-dihydro)q7-L-phenylalanine (DOPA) motif found in the foot protein of mussels. Although the exact mechanism of adhesion is not fully understood, it has been widely speculated that the 3,4-dihydro)qq3henyl (DHP) group of DOPA is responsible for the adhesion. When a polymer with DHP groups was placed in contact with a metal substrate, a thin polymer film was observed to spontaneously deposit on the surface. Functionalization of such a polymer was then able to impart new characteristics to the metal substrate. 

Schaefer et al. (19) studied the interphase microstructure of ternary polymer composites consisting of polypropylene, ethylene-propylene-diene-terpolymer (EPDM), and different types of inorganic fillers (e.g., kaolin clay and barium sulfate). They used extraction and dynamic mechanical methods to relate the thickness of absorbed polymer coatings on filler particles to mechanical properties. The extraction of composite samples with xylene solvent for prolonged periods of time indicated that the bound polymer around filler particles increased from 3 to 12 nm thick between kaolin to barium sulfate filler types. Solid-state Nuclear Magnetic Resonance (NMR) analyses of the bound polymer layers indicated that EPDM was the main constituent adsorbed to the filler particles. Without doubt, the existence of an interphase microstructure was shown to exist and have a rather sizable thickness. They proceeded to use this interphase model to fit a modified van der Poel equation to compute the storage modulus G (T) and loss modulus G"(T) properties. 

This section has discussed a diverse range of self-assembled synthetic macromolecules such as block copolymers and elastm-like polymers for template-directed assembly of different types of inorganic nanoparticles into anisotropic ID nanostructures. In the next section, we introduce a simple and cost-effective approach for directing the assembly of gold nanoparticles into ID structures via self-assembly of a short commercially available surfactant. 

Thus, inorganic polymers have a unique and distinct place in the family of polymers and they have the potential to fimction as unique materials. In this book we will examine some of the prominent members of inorganic polymers. There are many polymer types where sufficient examples do not exist or whose synthesis has not yet been shown to be general. Some of these polymers have been alluded to in this Chapter. However, they will not be covered elsewhere in this book. Dendrimeric materials, which are not linear polymers, are also not considered here. 

Polyphosphazenes, [N=PR2]n, are the largest family of inorganic polymers. Over 800 different types of polyphosphazenes are known [16, 21-23]. The common feature of all of these polymers is the backbone which is made up of alternate nitrogen and phosphorus atoms. While the nitrogen is trivalent and dicoordinate, phosphorus is pentavalent and tetracoordinate. Thus, nitrogen does not contain any substituents. Phosphorus, on the other hand, is attached to two substituents. Thus, the basic sfructural feature of the repeat unit of polyphosphazenes is exactly similar to what is found in cyclophosphazenes. 

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