Presentation on theme: "Polymers are large molecules made by linking together many smaller molecules, called monomers. Polymerization reactions can either be classified as addition."— Presentation transcript:
Polymers are large molecules made by linking together many smaller molecules, called monomers. Polymerization reactions can either be classified as addition reactions or as condensation reactions. Natural polymers include proteins, lipids and carbohydrates. Synthetic polymers include plastics, nylon, acetate, and polyesters. monomers polymer monomer symbol n
Synthetic Addition Polymers Addition polymerization is a reaction where monomer units join each other in a process that involves the rearranging of electrons in double or triple bonds in the monomer. - - - - Polyethylene: A Polymer of Ethene (Vinyl) Ethene has 2 pairs of shared e- in the double bond. High temperature or UV light can cause 2 of these shared (paired) electrons to become unshared (unpaired).
Here’s another way to see the chain reaction. These are the carbon atoms with their double- bond (2 shared electrons each). The hydrogen atoms are not shown. A collision breaks the first bond. Once the first double bond is broken, a chain reaction will occur. In about a second an entire chamber of compressed ethylene gas turns into the polymer, polyethylene.
When the chains get up to 500,000 carbons long, they are tough enough for synthetic ice, replacement joints, and bullet-proof vests. This is called high density polyethylene (HDPE). See p. 139 in textbook
That way they cannot lie next each other, which reduces the density and strength of the polyethylene. This makes the plastic lighter and more flexible. Low density polyethylene (LDPE) is made by causing the long chains of ethylene to branch.
Low density polyethylene is used to make things like plastic bags, plastic wrap, and squeeze bottles.
Polypropene It is more commonly called polypropylene. Polypropylene is used to make things like carpet, rope and thermal underwear.
Polyvinyl Chloride PVC is one of the most widely used polymers, with dozens of practical applications.
PolyVinyl Chloride (or PVC) is almost the same as polyethylene, except every second hydrogen is replaced with a chlorine atom (green sphere).
Teflon Teflon® is the product name for the polymer used to make nonstick cookware. It is composed of a series of tetrafluoroethene monomers. Recently, concern has been growing regarding the possibility that Teflon® releases toxic chemicals if it gets too hot.
19 Important constitutions for synthetic polymers
Crosslinking By using another atom – C group or OH or S the polymer can be strengthed and also control of the structure can be forced
Polyesters dicarboxylic acid + polyalcohol → polyester + water A polyester is a series of ester molecules joined in a long chain. The dicarboxylic acid has a carboxyl group at each end of the molecule and the polyalcohol (a diol) has a hydroxy group at each end. Polymers from Carboxylic Acids and Alcohols