Polymers Addition and Condensation Haley Ares Jimil Hartlen Isabelle Hansen

What is a Polymer? A polymer is a substance that has a large molecular mass, composed of many monomers (building block molecules) A monomer is the molecule that gets repeated to form a chain Each CH 2 CH 2 unit in the polymer comes from the ethylene monomer The double bonds from ethylene are converted into single bonds when the polymer is formed. One polyethylene can have thousands of ethylene monomers. H H \ / C = C / \ CH 2 CH 2 CH 2 ( CH 2 CH 2 ) 𝑛 CH 2 CH 2

Naming When naming a polymer you take the name of the monomer unit and add “Poly” in the front. If the monomer of a polymer was ethylene, the name of the polymer would be “Polyethylene”.

The “n” represents the fact that the CH 2 CH 2 can be repeated many times in the chain H H \ / C = C / \ CH 2 CH 2 CH 2 ( CH 2 CH 2 ) 𝑛 CH 2 CH 2 H H H H | | H H | | H - C – C – (C – C ) 𝑛 – C – C - H

Classification Polymers are classified according to their method of formation (addition or condensation) and according to their structure and properties Polymers that can be heated and melted without being destroyed, and return to their original condition once cooled are called thermoplastics. These chains are make with few cross-linked chains. Polymers that can’t be heated or melted without being destroyed are thermosetting polymers. They will not regain their structure when cooled. These are made of thoroughly cross-linked chains in a three-dimensional network.

Styrene monomer : H H \ / C -- C / \ H Addition The dots instead of a line on the top will make more sense later on. Many polymerization reactions proceed by means of a free radical mechanism. A free radical is an atom, ion, or molecule, which contains one or more unpaired electrons and they are reactive. Addition polymerization involves monomers that have double bonds. When making a polymer through free radical mechanism, the double bond becomes a single bond. This releases two electrons that allows for two new bonds to form.

A small amount of an initiator (a substance which will create free radicals) is mixed in with the monomer. Heating the mixture causes the initiator to break down into the free radicals. Heat – C – O – O – C – O O Benzyl Peroxide (initator) + 2 CO 2 Phenyl Free Radical Carbon Dioxide 2 This is what we need to create the polymer, along with the styrene from before.

\ / C -- C / \ H H H H H | | C C | | H The phenyl free radical acts with one end of the carbon-carbon bond of the styrene. The extra unpaired electron goes to the other side. H H \ / C -- C / \ H H H | | C C | | H This is the extra electron, placed on the end. The other electron will stay open to have multiple molecules connect. One of the double bond electron bonds with the phenyl.

The styrene molecule with the phenyl free radical will create a polystyrene chain. Theoretically, this growing chain could react with a phenyl free once again, but it is more likely that it will react with another similar growing chain. When the two free radical chains connect, the unpaired electron they each have will join up and create a covalently stable bond. H H | | C C | | H

Condensation These polymers form slowly, and require being heated for several hours to reach the proper chain length. They have low molecular mass compared to “addition polymers”, which is generally less than 100,000amu.

H 2 N – ( CH 2 ) 6 – NH 2 + HCO – ( CH 2 ) 4 – COH Nylons are well known types of condensation polymers. One of the best know nylon is made by a condensation reaction, with hexamethyldiamine and adipic acid. O O H 2 N – ( CH 2 ) 6 – NH 2 + HCO – ( CH 2 ) 4 – COH Hexamethyldiamine adipic acid H H O ------ NH( CH 2 ) 6 –N–C–( CH 2 ) 4 –C ------ + H 2 O Nylon O Water These mean the section shown is simply one repeating section of a larger chain.

} H H O ------ NH( CH 2 ) 6 –N–C–( CH 2 ) 4 –C ------ + H 2 O Nylon O Water The hexamethylenediamine unit alternates with the adipic acid unit. The N–C sections are the amide groups. Nylon is a polyamide. | H O Nylon’s molecular mass is around 25,000amu. It is used in textiles and to make gears and bearings. You can create nylon fibers by heating and forcing it through small holes. This can be used to make clothing, tire cord, rope, and brushes. }

Examples Polyethylene Terephthalate (PET) - carbonated drink bottles, peanut butter jars Polyethylene (PE) - supermarket bags, plastic bottles High-density Polyethylene - detergent bottles, milk jugs, molded plastic cases Polyvinyl Chloride (PVC) - plumbing pipes, shower curtains Polypropylene (PP) - Bottle caps, drinking straws, yogurt containers Polystyrene (PS) - disposable cups, plates and cutlery Polyamides (Nylons) - Fibers, toothbrush bristles, tubing

Other Information Polymer chains of different lengths can be made by the heating time, varying pressure, temperature and the amount of the reactants. The first plastic was produced in 1869 in answer to a newspaper contest which offered a $10 000 reward to the first person to produce a synthetic substitute for ivory billiard balls. There was concern that the large demand for ivory billiard balls would endanger the existence of elephant herds. Polymers that are used for useful end products are generally mixed with other chemicals to give them special properties. The basic polymer is referred to as resin. This resin comes in the form of powder or pellets. The polymerization reaction in the resin is completed when the other chemicals are added and then the polymer is made to it’s desired form

References https://sites.google.com/site/internationalgcsechemistry/year-11-topics/topic-5---synthetic- polymers-double-award/5---condensation-polymers http://www.edtechnetwork.com/powerpoint.html http://www.essentialchemicalindustry.org/polymers/polymers-an-overview.html http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/polymers.htm http://www.4college.co.uk/a/dp/condensation.php http://chemwiki.ucdavis.edu/Organic_Chemistry/Polymers/Addition_Polymers http://www.ausetute.com.au/polymers.html R.L. Whitman, E.E. Zinck, R.A. Nalepa. Chemistry Today, Second Edition. Canada. 1982. Print