Polymer Definition
Polymer define as a large molecule built up by the repetition of small, simple chemical units. Polymers are formed by polymerization process. In some cases the repetition is linear, much as chain is built up from its links. In other cases the chains are branched or interconnected to three dimensional networks. The repeat units of the polymer is usually equivalent or nearly equivalent to the monomer, or starting material from which the polymer is formed. Thus the repeat unit of polyvinyl chloride is -CH2CHCl -; its monomer is vinyl chloride, CH2=CHC.
The length of the of the polymer chain is specified by the number of repeat units in the chain. This is called the degree of polymerization (DP). The molecular weight of the polymer is the product of the molecular weight of the repeat unit and the DP. Using poly (vinyl chloride) as an example, a polymer of DP 1000 has a molecular weight of 63 x 1000 = 63,000. Most high polymers useful for plastics, rubbers, of fibers have molecular weights between 10,000 and 1,000,000.
Unlike many product whose structure and reactions were well known before their industrial application, some polymers were produced on an industrial scale long before their chemistry of physics was studied. Empiricism in recipes, processes, and control tests was usual.
Gradually the study of polymer properties began. Almost all were first called anomalous because they were so different from the properties of low molecular weight compounds. It was soon realized, however, that polymer molecules are many times larger than those of ordinary substances. The presumably anomalous properties of polymers were shown to be normal for such materials, as the consequences of their size were included in the theoretical treatments of their properties.
The length of the of the polymer chain is specified by the number of repeat units in the chain. This is called the degree of polymerization (DP). The molecular weight of the polymer is the product of the molecular weight of the repeat unit and the DP. Using poly (vinyl chloride) as an example, a polymer of DP 1000 has a molecular weight of 63 x 1000 = 63,000. Most high polymers useful for plastics, rubbers, of fibers have molecular weights between 10,000 and 1,000,000.
Unlike many product whose structure and reactions were well known before their industrial application, some polymers were produced on an industrial scale long before their chemistry of physics was studied. Empiricism in recipes, processes, and control tests was usual.
Gradually the study of polymer properties began. Almost all were first called anomalous because they were so different from the properties of low molecular weight compounds. It was soon realized, however, that polymer molecules are many times larger than those of ordinary substances. The presumably anomalous properties of polymers were shown to be normal for such materials, as the consequences of their size were included in the theoretical treatments of their properties.
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