What is Polymerization? - Definition, Types & Examples

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  • 0:00 Polymer Principles
  • 1:01 Addition Polymerization
  • 1:43 Condensation…
  • 3:26 Variety
  • 4:10 Lesson Summary
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Lesson Transcript
Instructor: Anthony Grattini

Tony has a BA in Biology and has taught secondary Life, Earth, and Physical Science, as well as Honors & AP Chemistry.

In this lesson, learn about the process of polymerization. Explore the two major types, common polymers, and some of the chemistry involved with this biologically and commercially important chemical reaction.

Polymer Principles

'Polymer' comes from the Greek, meaning 'many parts.' A polymer is a long molecule consisting of many identical or similar building blocks linked by covalent bonds - like how a train consists of a chain of cars. Most large molecules, or macromolecules, are polymers. The repeating units that serve as the building blocks of a polymer are small molecules called monomers.

How are these monomers put together? Polymerization is the process of connecting these monomers together and creating large macromolecules of different sizes and shapes. Polymerization is similar to constructing a large building out of the same type of Lego blocks. The blocks can be connected in various ways to create a larger, more intricately shaped structure than the original Lego block on its own.

The two major types of polymerization are addition polymerization and condensation polymerization.

Addition Polymerization

Polymerization that occurs through the coupling of monomers using their multiple bonds is called addition polymerization. The simplest example involves the formation of polyethylene from ethylene molecules. In this reaction, the double bond in each ethylene molecule opens up, and two of the electrons originally in this bond are used to form new carbon-carbon single bonds with two other ethylene molecules.

Some common commercial addition polymers are:

  • Polyethylene - films, packaging, bottles
  • Polypropylene - kitchenware, fibers, appliances
  • Polyvinyl chloride - pipe fittings, clear film for meat packaging

Condensation Polymerization and Hydrolysis

The chemical mechanism that cells use to make and break polymers are basically the same in all cases. Monomers are connected by a reaction in which two molecules are covalently bonded to each other through loss of a water molecule; this is called a condensation polymerization because the lost molecule is water. When a bond forms between two monomers, each monomer contributes part of the water molecule that is lost; one molecule provides a hydroxyl group, while the other provides a hydrogen. To make a polymer, this reaction is repeated as monomers are added to the chain one by one.

Polymers are disassembled to monomers by hydrolysis, a process that is essentially the reverse of the dehydration reaction. 'Hydrolysis,' from Greek, means to 'break with water.' Bonds between monomers are broken by the addition of water molecules, a hydrogen from the water attaching to one monomer and a hydroxyl attaching to the adjacent monomer.

The process of digestion in our bodies is an example of hydrolysis. The bulk of the organic material in our food is in the form of polymers that are much too large to enter our cells. Hydrolysis helps to break these polymers into absorbable bits within the digestive tract.

Some common polymers in life are:

  • Disaccharides and polysaccharides like maltose, sucrose, and glycogen
  • All proteins made from amino acids
  • Nucleic acids, like DNA and RNA, made from nucleotides

Some common commercial condensation polymers are:

  • Polyurethane
  • Polyethylene terephthalate (a polyester)
  • Nylon 6,6

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