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Polymerization Reactions. What is Polymerization?. Polymerization is a process in which very small molecules, called monomers, combine chemically with each other to produce a very large chainlike molecule, called a polymer. The First Polymerization.
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What is Polymerization? • Polymerization is a process in which very small molecules, called monomers, combine chemically with each other to produce a very large chainlike molecule, called a polymer.
The First Polymerization • The first synthetic polymer was discovered in 1909 by Leo Backeland, a Belgian-born US Chemist. • It was marketed under the trademark Bakelite, which was made from phenol and formaldehyde. • It became an important plastic and resin for adhesives, and paints.
Polymerization Types • There are two main types of Polymerization reactions: • Addition • Condensation 2 + 2 Think water, although that is not always the case
Addition Polymerization • In Addition Polymerization, monomers form without a by-product, such as water. • The structure has one structural unit, or monomer, that occurs repeatedly. • The monomer molecules may be all alike, or they may represent two, three, or more different compounds. The Addition Reaction involves only double and single bonded compounds.
Addition Polymerization • Through polymerization of ethylene (ethene), CH2CH2, the structure of the polymer can be represented by -(CH2CH2)n- where n can be several thousand. • Example: H H H H H H H H H H H H | | | | | | | | | | | | C=C + C=C + C=C => :C-C:C-C:C-C: | | | | | | | | | | | | H H H H H H H H H H H H ethylene part of polyethylene OR -(CH2CH2)n- • Because of this, polymers have incredible molar masses up to millions of grams per mole.
Addition Polymerization • The elastic property of rubber is due to the flexibility of the long chain molecules. • In 1839, American chemist Charles Goodyear discovered that natural rubber could be cross-linked with sulfur. This would prevent the long chains from slipping. • This process was known as vulcanization. • It paved that way for many practical and commercial usage, including using vulcanized rubber for automobile tires.
Free Radical Polymerization • Free-Radical Addition is another type of polymerization reaction. This is when the polymer is induced by an initiator, which is a compound that produces free radicals. • Free-radicals are species that have an unpaired electron.
Condensation Polymerization • In condensation polymerization, two functional groups of two different monomer molecules are joined together which produces a small molecule such as water. Remember the water? • The monomers bond at where the hydrogen atoms were taken out to produce water. In order to become a condensed polymer, the monomer molecules must have at least two functional groups.
Condensation Polymerization • The reaction between a carboxylic acid and an alcohol creates an ester. • If the carboxylic acid and the alcohol were the monomers of the polymer, during polymerization, they would create polyester, and produce water.
Condensation Polymerization • Example of condensation polymerization: Curing of concrete • There are several types of materials that form by Condensation Polymerization, including nylon, polyesters, rayon, and spandex.
