Polymeric materials polycarbonates

Just as many small-molecule materials, polymers also form glasses [4]. Actually, most polymeric materials of everyday use are made of polymer glasses, polystyrene (PS) cups or compact discs made of polycarbonates, for instance. In many respects polymer glasses are very similar to small-molecule glasses, and there is nothing special about them. However, on the other hand, the special aspects of polymer materials allow specific studies beyond characteristic studies on small-molecule glasses. 

Membranes used for the pressure driven separation processes, microfiltration (MF), ultrafiltration (UF) and reverse osmosis (RO), as well as those used for dialysis, are most commonly made of polymeric materials. Initially most such membranes were cellulosic in nature. These ate now being replaced by polyamide, polysulphone, polycarbonate and several other advanced polymers. These synthetic polymers have improved chemical stability and better resistance to microbial degradation. Membranes have most commonly been produced by a form of phase inversion known as immersion precipitation.11 This process has four main steps ... 

Whereas the tensile strength was not a sensitive function of the monomer structure, the tensile modulus (Young s Modulus) was clearly related to the monomer structure. This is expected since the tensile modulus is a measure of the polymer s resistance to deformation and is related to the "stiffness" of a polymeric material. The highest tensile modulus (22,000 kg/cm2,2.2 GPa) was measured for poly(BPA iminocarbonate). Replacement of BPA by Dat-Tyr-Hex reduced the tensile modulus significantly. This observation can possibly be attributed to the presence of the long hexyl ester pendent chain in Dat-Tyr-Hex. Generally, the polyiminocarbonates were somewhat "stiffer" than the corresponding polycarbonates. Thus, the tensile moduli of poly(Dat-Tyr-Hex iminocarbonate) and poly(Dat-Tyr-Hex carbonate) were 16,300 kg/cm2 (1.6 GPa) and 13,900 kg/cm2 (1.3 GPa) respectively. 

In the first stage in order to test the process of various types of polymer films were surface-fluorinated. From 1990 to 1994 it was shown that XeF2 could be used effectively for surface fluorination of a variety of plastics. Polyethylene film and plates,18 aromatic polysulfone,19 polyvinyltrimethylsilane,20 and polycarbonate,21 among other polymeric materials, were fluorinated successfully. 

Processors Some companies manufacture their own polymeric materials for subsequent processing, but the majority purchases the necessary polymeric materials from other companies. Processors may specialize in the use of selected polymers, such as nylons and polycarbonates, or focus on particular techniques of processing, such as coatings, films, sheets, laminates, and bulk molded and reinforced plastics. 

Ulmer II CW, Smith DA, Sumpter BG et al. (1998) Computational neural networks and the rational design of polymeric materials the next generation polycarbonates. Comput Theor Polym Sci 8 311-321... 

Abstract This chapter focuses on well-defined metal complexes that serve as homogeneous catalysts for the production of polycarbonates from epoxides or oxetanes and carbon dioxide. Emphasis is placed on the use of salen metal complexes, mainly derived from the transition metals chromium and cobalt, in the presence of onium salts as catalysts for the coupling of carbon dioxide with these cyclic ethers. Special considerations are given to the mechanistic pathways involved in these processes for the production of these important polymeric materials. 

Carbon dioxide is a widely available, inexpensive, and renewable resource. Hence, its utilization as a source of chemical carbon or as a solvent in chemical synthesis can lead to less of an impact on the environment than alternative processes. The preparation of aliphatic polycarbonates via the coupling of epoxides or oxetanes with CO2 illustrates processes where carbon dioxide can serve in both capacities, i.e., as a monomer and as a solvent. The reactions represented in (1) and (2) are two of the most well-studied instances of using carbon dioxide in chemical synthesis of polymeric materials, and represent environmentally benign routes to these biodegradable polymers. We and others have comprehensively reviewed this important area of chemistry fairly recently. Nevertheless, because of the intense interest and activity in this discipline, regular updates are warranted. 

Segal, D., Chemical Synthesis of Advanced Ceramic Materials, Cambridge Univ. Press, New York, 1991. Sehanobish K., H. T. Pham, and C. P. Bosnyak, Polycarbonates (Overview), in Polymeric Materials Encyclopedia, J. C. Salamone, ed., CRC Press, Boca Raton, FL, 1996. 

The following listing of common polymers provides respective structured The reader should note that the name of the polymer often provides the key to its representative structure. There are, however, names such as polycarbonate that can represent a variety of polymeric materials. f j... 

The density or its reciprocal, the specific volume, is a commonly used property for polymeric materials. The specific volume is often plotted as a function of pressure and temperature in what is known as a pvT diagram. A typical pvT diagram for an unfilled and filled amorphous polymer is shown, using polycarbonate as an example, in Figs. 2.10 and 2.11 The two slopes in the curves represent the specific volume of the melt and of the glassy amorphous polycarbonate, separated by the glass transition temperature. 

Because of the high functionality of glycerol it is not surprising that a significant amount of research has focused on new polymeric materials that incorporate glycerol (Fig. 8.4). This includes polyesters, poly ethers, and polycarbonates (Ray and Grinstaff, 2003 Fu et al., 2003). In addition to the linear and network polymers, dendritic or hyperbranched structures have been investigated extensively (Malmstrom et al., 1995 Hawker et al., 1997 Jayaraman and Frechet, 1998 Bosnian et al., 1999 Sunder et al., 1999, 2000 ... 

Several compounds with the formula C Sj, are known (Fig. 7-10). Most of them are molecular compounds, but a few polymeric materials such as (CS2), (CS) , and (C3S5), have also been described. Polycarbon sulfide displays high electrical conductivity. 

It has been shown that it is possible to effectively reduce the flammability of many polymeric materials by using metal compounds in very low concentrations. Metals and their compounds may be included in the polymeric macrochains, either coordi-natively bonded to functional groups of the polymer or used as additives. For example optically transparent, low-flammability polycarbonates have been obtained by adding as little as 0.001 to 2 % by weight of alkali or alkaline earth metal sulfonates... 

Other polymeric materials (Figure 3.7) including polystyrene, polyvinylchloride (PVC), polytetrafluoroethylene (PTFE), polyvinylenedifluorate (PVDF), polyacrylonitrile (PAN), polycarbonates, polyacrylates and polymethacrylates, polyetherur-ethane, as well as various inorganic materials have been used as chromatographic supports. 

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