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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. How are the pictures of DNA different?
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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.
How are the pictures of DNA different? Identify the trimer of DNA. What are the cross-linkers?
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 • In 1839, American chemist Charles Goodyear discovered that natural rubber could be cross-linked with sulfur. • This process was known as vulcanization.
How are Free Radicals Used in Polymerization? Free-Radical Addition is another type of polymerization reaction. This is when the polymer is induced (started) by an initiator, which is a compound that produces free radicals
What Free Radicals Are NOT Hey, these radicals Are still free! Don’t They need to be Arrested?
What Free Radicals Are NOT Ah, Out from under at last!!! 2 Your math teacher would not approve
What a Free Radical IS • Free-radicals are species that have an unpaired electron.
What does an “unpaired” electron mean? Remember the electron configuration thing? Well, an unpaired electron is when An orbital has only an electron with one spin (either +1/2 or -1/2) Example: 1s2 2s1 Example 1s22s22p5 In a compound an UNPAIRED electron is one that is unbonded
Condensation Polymerization • In condensation polymerization, two functional groups of two different monomer molecules are joined together which produces a small molecule such as water. • The monomers bond 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.