Monomers, synthetic

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Polymers are made by chemically joining together many small molecules into one giant molecule, or macromolecule. The small molecules used to synthesize polymers are called monomers. Synthetic polymers can be classified as addition polymers, made by monomer units directly joined together, or condensation polymers, made by monomer units combining so that a small molecule, usually water, is split out between them. 

Dendrimers are hyper-branched nano-structures, made by a large number of (one or more types) substructures called monomers, synthetically joined within a rigorously tailored architecture (TomaUa et al. 1990 Newkome et al. 2(X)1 Diudea and Katona 1999). They can be functionalized at terminal branches, thus finding a broad pallet of applications in chemistry, medicine, etc. 

Polymer. A high molecular weight organic compound, natural or synthetic, whose structure can be represented by a repeated small unit, the monomer. Synthetic polymers are formed by addition or condensation polymerization of monomers. When two or more monomers are involved, the product is called a copolymer. 

A few examples of catalytic two-phase processes are given in Table 5.1. As can be seen in the table, the processes introduced are, first and foremost, reactions in the inorganic bulk chemical industry such as the manufacture of ammonia, sulfuric acid, nitric acid, and reactions in the petrochemical industry such as the manufacture of monomers, synthetic fuels, hydrogenations, dehydrogenations, dearomatizing reactions, and so on. 

Because these materials are polymerized at acid pH to ensure incorporation of the acidic monomer, synthetic surfactants such as dode-cylbenzene sulfonic acid are used. Normally the pH of the system is raised with alkali at the end of reaction and the product is sold in the range of pH 6-10 depending on manufacturing process and grade. 

Acrilan A brand name for a synthetic fibre, based on a copolymer of acrylonitrile with minor proportions of other unspecified vinyl monomers. See also propenenitrile. 

A polymer is a macromolecule that is constructed by chemically linking together a sequent of molecular fragments. In simple synthetic polymers such as polyethylene or polystyrer all of the molecular fragments comprise the same basic unit (or monomer). Other poly me contain mixtures of monomers. Proteins, for example, are polypeptide chains in which eac unit is one of the twenty amino acids. Cross-linking between different chains gives rise to j-further variations in the constitution and structure of a polymer. All of these features me affect the overall properties of the molecule, sometimes in a dramatic way. Moreover, or... 

Di- and trinucleotides may be used as units instead of the monomers. This convergent synthetic strategy simplifies the purification of products, since they are differentiated by a much higher jump in molecular mass and functionality from the educls than in monomer additions, and it raises the yield. We can illustrate the latter effect with an imaginary sequence of seven synthetic steps, c.g. nucleotide condensations, where the yield is 80% in each step. In a converging seven-step synthesis an octanucleotide would be obtained in 0.8 x 100 = 51% yield, compared with a 0.8 x 100 = 21% yield in a linear synthesis. 

Just as it is not necessary for polymer chains to be linear, it is also not necessary for all repeat units to be the same. We have already mentioned molecules like proteins where a wide variety of different repeat units are present. Among synthetic polymers, those in which a single kind of repeat unit are involved are called homopolymers, and those containing more than one kind of repeat unit are copolymers. Note that these definitions are based on the repeat unit, not the monomer. An ordinary polyester is not a copolymer, even though two different monomers, acids and alcohols, are its monomers. By contrast, copolymers result when different monomers bond together in the same way to produce a chain in which each kind of monomer retains its respective substituents in the polymer molecule. The unmodified term copolymer is generally used to designate the case where two different repeat units are involved. Where three kinds of repeat units are present, the system is called a terpolymer where there are more than three, the system is called a multicomponent copolymer. The copolymers we discuss in this book will be primarily two-component molecules. We shall discuss copolymers in Chap. 7, so the present remarks are simply for purposes of orientation. 

Uses. Furfuryl alcohol is widely used as a monomer in manufacturing furfuryl alcohol resins, and as a reactive solvent in a variety of synthetic resins and appHcations. Resins derived from furfuryl alcohol are the most important appHcation for furfuryl alcohol in both utihty and volume. The final cross-linked products display outstanding chemical, thermal, and mechanical properties. They are also heat-stable and remarkably resistant to acids, alkaUes, and solvents. Many commercial resins of various compositions and properties have been prepared by polymerization of furfuryl alcohol and other co-reactants such as furfural, formaldehyde, glyoxal, resorcinol, phenoHc compounds and urea. In 1992, domestic furfuryl alcohol consumption was estimated at 47 million pounds (38). 

Methyl mbber, obtained by polymerization of this monomer, was expensive and had inferior properties, and its manufacture was discontinued at the end of Wodd War 1. By the time Wodd War 11 again shut off access to natural mbber, Germany had developed better synthetic mbbers based upon butadiene... 

Acroleiu, iu lARC Monographs on the Evaluation of Carcinogenic Risk of Chemicals to Humans. Some Monomers, Plastics and Synthetic Elastomers andMcrolein, Vol. 19, International Agency for Research on Cancer, Lyon, France, 1979, pp. 479—494. 

Synthetic emulsion polymers account for approximately 70% of the U.S. consumption of acrylate monomers. Major end uses for these latex polymers are coatings (32%), textiles (17%), adhesives (7%), paper (5%), and floor poHshes (3%). The U.S. producers of acryflc copolymer emulsions include Rohm and Haas, Reichhold, National Starch, Union Carbide, Air Products, Unocal, B. F. Goodrich, and H. B. Fuller. 

Uses. Vinyhdene fluoride is used for the manufacture of PVDF and for copolymerization with many fluorinated monomers. One commercially significant use is the manufacture of high performance fluoroelastomers that include copolymers of VDF with hexafluoropropylene (HFP) (62) or chlorotrifluoroethylene (CTFE) (63) and terpolymers with HEP and tetrafluoroethylene (TEE) (64) (see Elastomers, synthetic-fluorocarbon elastomers). There is intense commercial interest in thermoplastic copolymers of VDE with HEP (65,66), CTEE (67), or TEE (68). Less common are copolymers with trifluoroethene (69), 3,3,3-trifluoro-2-trifluoromethylpropene (70), or hexafluoroacetone (71). Thermoplastic terpolymers of VDE, HEP, and TEE are also of interest as coatings and film. A thermoplastic elastomer that has an elastomeric VDE copolymer chain as backbone and a grafted PVDE side chain has been developed (72). 

Polyols. Several important polyhydric alcohols or polyols are made from formaldehyde. The principal ones include pentaerythritol, made from acetaldehyde and formaldehyde trimethylolpropane, made from -butyraldehyde and formaldehyde and neopentyl glycol, made from isobutyraldehyde and formaldehyde. These polyols find use in the alkyd resin (qv) and synthetic lubricants markets. Pentaerythritol [115-77-5] is also used to produce rosin/tall oil esters and explosives (pentaerythritol tetranitrate). Trimethylolpropane [77-99-6] is also used in urethane coatings, polyurethane foams, and multiftmctional monomers. Neopentyl glycol [126-30-7] finds use in plastics produced from unsaturated polyester resins and in coatings based on saturated polyesters. 

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