Use of inorganic polymers

This so-called polymer route was introduced by Chantrell and Popper [10], who proposed the use of inorganic polymers as starting materials for the preparation of ceramics, opening up the rather ambitious perspective of easily shaping monolithic green bodies via this route. At the end of the 1960s, Winter et al. [11, 12] pioneered such a process for the production of Si/C/N fibers, and developed it to technical feasibility. Following the route developed by Yajima et al. [13, 14], ceramic fibers (SiC, Nicalon) have been available on... 

The use of inorganic polymers as processible ceramic precursors remains a major area of study. In the section on sol-gel chemistry, new systems, property studies, and methods for controlling particle size and porosity are discussed. In the paper by Schmidt (Chapter 15), some potential optic applications and applications as anti-soil or corrosion resistant coatings of several such systems are presented. Livage (Chapter 12) outlines the preparation of mbced metd oxopolymers, while Barron (Chapter 13) and Rees (Chapter 14) report on improved methods for the synthesis of aluminum oxopolymers. Drinker (Chapter 10) reports on the influence of Idnetic effects on ceramic film structures formed by sol-gel methods. 

The use of organic polymers offers several advantages over the use of inorganic coagulants ... 

The apphcation of a high electric field across a thin conjugated polymer film has shown the materials to be electroluminescent (216—218). Until recentiy the development of electroluminescent displays has been confined to the use of inorganic semiconductors and a limited number of small molecule dyes as the emitter materials. Expansion to the broad array of conjugated polymers available gives advantages in control of emission frequency (color) and facihty in device fabrication as a result of the ease of processibiUty of soluble polymers (see Chromogenic materials,electrochromic). 

Casein may be considered to be a conjugated protein, that is the protein is associated in nature with certain non-protein matter known as prosthetic groups. In the case of casein the prosthetic group is phosphoric acid. The protein molecule is also associated in some way with calcium. The presence of these inorganic materials has an important bearing on the processability and subsequent use of casein polymers. 

The approach to standardization used by Haaijman (53) and others (66,67), in which the fluorophor is incorporated within or bound to the surface of a plastic sphere, is more versatile than the use of inorganic ion>doped spheres, since the standard can be tailored exactly to the specifications required by the analyte species. However, this approach increases the uncertainty of the measurement because the photobleaching characteristics of both the standard and the sample must be considered. The ideal approach is to employ both types of standards. The glass microspheres can be used to calibrate instruments and set instrument operating parameters on a day-to-day basis, and the fluorophor-doped polymer materials can be used to determine the concentration-instrument response function. 

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. 

One potential solution to these problems, suggested some 20 years ago by Chantrell and Popper (1), involves the use of inorganic or organo-metallic polymers as precursors to the desired ceramic material. The concept (2) centers on the use of a tractable (soluble, meltable or malleable) inorganic precursor polymer that can be shaped at low temperature (as one shapes organic polymers) into a coating, a fiber or as a matrix (binder) for a ceramic powder. Once the final shape is obtained, the precursor polymer can be pyrolytically transformed into the desired ceramic material. With careful control of the pyrolysis conditions, the final piece will have the appropriate physical and/or electronic properties. 

This is one of the main purposes of inorganic polymer research —the search for new and useful compounds and materials that combine the properties of polymers with those of ceramics and/or metals. 

The use of inorganic additives as extenders in thermoplastic polymers is a long established practice. In recent years, the role of such additives has changed from that of cost-reducing fillers to property enhancing reinforcing agents. This conversion has come about as a result of the comp tibilization of the additive with the thermoplastic polymer, by interaction at the polymer-filler interface. 

Portland cement is the least expensive, most widely used synthetic inorganic polymer. It is employed as the basic nonmetallic, nonwoody material of construction. Concrete highways and streets span our countryside and concrete skyscrapers silhouette the urban skyline. Less spectacular uses are found in everyday life as sidewalks, fence posts, and parking bumpers. 

This chapter initially provides an overview of the considerations associated with the synthesis of inorganic polymers and the reasons why inorganic rings are so important as polymer precursors. The methods commonly used to characterise polymers are then discussed. As in Chapter 3, which describes the techniques used for the characterisation of inorganic rings, this section focuses on utility rather than on theoretical and practical details of the different methods. The reader is referred to a variety of texts for further details about these polymer structural characterisation techniques. ... 

For the purpose of this argument, however, let us say that the biphasic system appears to be needlessly complicated. The reason for this might be the need for precise temperature control, not always possible in the field. Separation of the phases is possible but problematic on a large scale. Contamination by the use of inorganic salts to insolubilize the polymer precludes injecting groundwater back into the ground. 

The polymers which have been used to illustrate problems of inorganic polymer formation have been lieteroatomic. that is, their chains are built from different atoms alternating with each other. The other structure mentioned has been homoatomic—all the atoms in the chain are the same. There aie only a few homoatomic polymers of airy promise. Most elements will form only cyclic materials of low molecular weight if they polymerize at all. In addition to the silane polymers, black phosphorus, a high-pressure modification of the element, forms in polymeric sheets. 

There are several important reasons for wanting to know molecular weights in polymer science. From the viewpoint of inorganic polymers, the main uses are for the interpretation of molecular-weight dependent properties, and for the elucidation of polymerization mechanisms. The latter involves characterization of the molecular weight distribution, which is the subject of the following section. 

A promising approach to improving PMC performance is the use of inorganic barrier coatings to block the interaction of oxygen and oxy-radicals with the polymer surface. The effectiveness and durability of the coatings will depend on the thermal stability, compactness, and uniformity of the coating... 

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