Synthetic polymers physical properties

Synthetic Polymers Physical Properties and Methods of Preparation of Nanoparticles... 

Hadjichristidis, N., H. Iatrou, S. Pispas, andM. Pitsikalis, J. Polym. Sci. Polym. Chem. Ed., 38,3211 (2000). Hadjichristidis, N., M. Pitsikalis, S. Pispas, and H. Iatrou, Chem. Rev., 101, 3747 (2001). Hadjichristidis, N., S. Pispas, and G. Floudas, Block Copolymers Synthetic Strategies, Physical Properties, and Applications, Wiley, New York, 2002. 

Nikos Hadjichristidis has dedicated his career primarily to the synthesis of model polymers with complex macromolecular architectures and has published more than 370 papers and 23 reviews in refereed scientific journals, 6 patents, two books (as editor), and is the author of Block Copolymers Synthetic Strategies, Physical Properties, and Applications (2003). 

Introducing boryl substituents into a polymer not only influences polymer physical properties but also provides a reactive functional group that can undergo further chemical modification. The development of boron-fimctionahzed polymers has been slow compared with that of other ffinc-tionahzation methods of diene polymers due to the hydrolytic and oxidative sensitivity of many boron-containing molecules. However, new synthetic methods developed over the years have made easier the synthesis of boron-containing polymers with better long-term stability. Recently, the unique electronic and photophysical properties and Lewis acidic character of boron-containing polymers have attracted attention for the development of novel optical and sensor materials. " ... 

The level of technical service support provided for a given product generally tracks in large part where the suppHer considers thek product to be located within the spectmm of commodity to specialty chemicals. Technical service support levels for pure chemicals usually provided in large quantities for specific synthetic or processing needs, eg, ammonia (qv), sulfuric acid (see SuLFURic ACID AND SULFURTRIOXIDe), formaldehyde (qv), oxygen (qv), and so forth, are considerably less than for more complex materials or blends of materials provided for multistep downstream processes. Examples of the latter are many polymers, colorants, flocculants, impact modifiers, associative thickeners, etc. For the former materials, providing specifications of purity and physical properties often comprises the full extent of technical service requked or expected by customers. These materials are termed undifferentiated chemicals (9),... 

This article discusses traditional hull ding and construction products, ie, not made from synthetic polymers (see Building materials, plastic), including wood, asphalt, gypsum, glass products, Pordand cement, and bricks. The article presents information about each basic material, the products made from it, the basic processes by which the products or materials are produced, estimates of the quantity or doUar value of the quantities produced or used in the United States, and some pertinent chemical or physical properties related to the material. More detailed chemical and physical property data can be found in articles devoted to the individual materials (see Asphalt Cement Glass Wood). 

Acrylic Resins. The first synthetic polymer denture material, used throughout much of the 20th century, was based on the discovery of vulcanised mbber in 1839. Other polymers explored for denture and other dental uses have included ceUuloid, phenolformaldehyde resins, and vinyl chloride copolymers. Polystyrene, polycarbonates, polyurethanes, and acryHc resins have also been used for dental polymers. Because of the unique combination of properties, eg, aesthetics and ease of fabrication, acryHc resins based on methyl methacrylate and its polymer and/or copolymers have received the most attention since their introduction in 1937. However, deficiencies include excessive polymerization shrinkage and poor abrasion resistance. Polymers used in dental appHcation should have minimal dimensional changes during and subsequent to polymerization exceUent chemical, physical, and color stabiHty processabiHty and biocompatibiHty and the abiHty to blend with contiguous tissues. 

Grafting reactions alter the physical and mechanical properties of the polymer used as a substrate. Grafting differs from normal chemical modification (e.g., functionalization of polymers) in the possibility of tailoring material properties to a specific end use. For example, cellulose derivatization improves various properties of the original cellulose, but these derivatives cannot compete with many of the petrochemically derived synthetic polymers. Thus, in order to provide a better market position for cellulose derivatives, there is little doubt that further chemical modification is required. Accordingly, grafting of vinyl monomers onto cellulose or cellulose derivatives may improve the intrinsic properties of these polymers. 

The chemistry of synthetic polymers is similar to the chemistry of small molecules with the same functional groups, but the physical properties of polymers are greatly affected by size. Polymers can be classified by physical property into four groups thermoplastics, fibers, elastomers, and thermosetting resins. The properties of each group can be accounted for by the structure, the degree of crystallinity, and the amount of cross-Jinking they contain. 

Poly(p-pheny lene)s, PPPs, constitute the prototype of rigid-rod polymers and are currently being intensively investigated [1]. The key role of PPPs follows from their conceptually simple and appealing molecular structure, from their chemical stability, and from their superior physical properties [2], In turn, this is the result of important advances made in aromatic chemistry over the last few years. The following section gives an overview of the most common methods to generate poly(p-phenylene)s via different synthetic approaches. 

This article, while not being intended to provide a full account of poly(arylene)s, emphasises the synthetic aspects. The synthesis of conjugated oligomers and polymers is, however, always part of an interdisciplinaiy approach with their active physical function being a key concern. In that sense the research being reviewed above concentrates on physical properties rather than playing with exotic chemical structures. 

In general. Figure 9-2 b to c show strategies to make conjugated polymers more proeessible but it must be noted that the different synthetic approaches do not only result in different degrees of (a) chemical purity but also alter (b) the physical properties due lo intrinsic differences. Compared to a pure conjugated... 

The application of NMR spectroscopy to tacticity determination of synthetic polymers was pioneered by Bovey and Tiers.9 NMR spectroscopy is the most used method and often the only technique available for directly assessing tacticity of polymer chains. "2 7 8 0JI The chemical shift of a given nucleus in or attached to the chain may be sensitive to the configuration of centers three or more monomer units removed. Other forms of spectroscopy (e.g. TR spectroscopy l2 lJ) are useful with some polymers and various physical properties (e.g. the Kerr effect14) may also be correlated with tacticity. 

Hydrogen sulphide occurs naturally, e.g. in natural gas and petroleum, volcanic gases, and from decaying organic matter. It may be present near oil wells and where petroleum is processed. Commercially it is obtained as a by-product from many chemical reactions including off-gas in the production of some synthetic polymers (e.g. rayon, nylon) from petroleum products, and by the action of dilute mineral acids on metal sulphides. Physical properties are summarized in Table 9.14 and effects of temperature on vapour pressure are shown in Figure 9.5. 

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