CH 104: THE SYNTHESIS OF COMMON POLYMERSCH 104: THE SYNTHESIS OF COMMON POLYMERS

• PolymersPolymers are long chains of repeating units called are long chains of repeating units called monomersmonomers. Literally, polymers are many (. Literally, polymers are many (polypoly) small units ) small units ((merosmeros). Monomers are one (). Monomers are one (monomono) small unit () small unit (meromero).).

• Examples of natural polymers include DNA and RNA (from Examples of natural polymers include DNA and RNA (from nucleic acids), proteins (from amino acids), starch and nucleic acids), proteins (from amino acids), starch and cellulose (from glucose), and rubber (from isoprene).cellulose (from glucose), and rubber (from isoprene).

• Examples of manmade polymers include Examples of manmade polymers include polyethylene, polypropylene, polyester, polyethylene, polypropylene, polyester, polyurethane, polyvinylchloride (PVC), polyurethane, polyvinylchloride (PVC), epoxy, nylon, slime, silicone rubber, epoxy, nylon, slime, silicone rubber, Dacron, Kevlar, Lucite, Orlon, and Dacron, Kevlar, Lucite, Orlon, and Teflon.Teflon.

• In today’s experiment you will make In today’s experiment you will make nylon, slime, and silicone rubber.nylon, slime, and silicone rubber.

CHEMICAL STRUCTURES OF POLYMERSCHEMICAL STRUCTURES OF POLYMERS

• In simplest terms, a polymer is made by repeatedly adding In simplest terms, a polymer is made by repeatedly adding 1,000 to 1,000,000 or more monomers to a molecule.1,000 to 1,000,000 or more monomers to a molecule.

Many A → etc. –A – A – A – A – etc. or (– A –)Many A → etc. –A – A – A – A – etc. or (– A –)nn

• A A copolymercopolymer has 2 or more alternating monomers. has 2 or more alternating monomers.

Many A + Many B → etc. –A – B – A – B – etc. or (– A – B –)Many A + Many B → etc. –A – B – A – B – etc. or (– A – B –)nn

CLASSIFYING POLYMERS BY SYNTHESISCLASSIFYING POLYMERS BY SYNTHESIS

• Addition polymersAddition polymers are made from monomers that link together without are made from monomers that link together without losing any atoms. These monomers typically have at least 1 carbon-losing any atoms. These monomers typically have at least 1 carbon-carbon double bond. Polyethylene is an addition polymer.carbon double bond. Polyethylene is an addition polymer.

• Condensation polymersCondensation polymers are made from monomers that link together are made from monomers that link together and lose small molecules such as water (Hand lose small molecules such as water (H22O), ammonia (NHO), ammonia (NH33), or ), or

hydrogen chloride (HCl). These monomers have 2 or more reactive hydrogen chloride (HCl). These monomers have 2 or more reactive functional groups. Most condensation polymers are copolymers. functional groups. Most condensation polymers are copolymers. Dacron is a condensation polymer.Dacron is a condensation polymer.

CLASSIFYING POLYMERS BY STRUCTURECLASSIFYING POLYMERS BY STRUCTURE

• Polyethylene is a Polyethylene is a linear polymerlinear polymer..

• Polypropylene is a Polypropylene is a branched polymerbranched polymer..

• Kevlar is a Kevlar is a cross-linked polymercross-linked polymer..The polymer chains of Kevlar The polymer chains of Kevlar crystallize in parallel, like dry crystallize in parallel, like dry spaghetti noodles in a box. These spaghetti noodles in a box. These parallel chains are cross-linked with parallel chains are cross-linked with hydrogen bonds. As a result, Kevlar hydrogen bonds. As a result, Kevlar is 5 times stronger than steel. It is is 5 times stronger than steel. It is used in bulletproof vests, helmets, used in bulletproof vests, helmets, suspension bridge cables, and radial suspension bridge cables, and radial tires.tires.

CLASSIFYING POLYMERS BY THERMAL PROPERTIESCLASSIFYING POLYMERS BY THERMAL PROPERTIES

• In contrast, a cross-linked polymer is essentially 1 gigantic molecule. In contrast, a cross-linked polymer is essentially 1 gigantic molecule. The cross-links are strong bonds that make an irregular 3-dementional The cross-links are strong bonds that make an irregular 3-dementional structure. Therefore, these structure. Therefore, these thermoset plasticsthermoset plastics do not soften when do not soften when heated. In fact, heating can produce more cross-links and make the heated. In fact, heating can produce more cross-links and make the material even harder. Kevlar is a thermoset plastic.material even harder. Kevlar is a thermoset plastic.

• Linear and branched polymers are long molecules Linear and branched polymers are long molecules that are more or less crystalline. They interact in that are more or less crystalline. They interact in these crystals through weak dipole-dipole forces. these crystals through weak dipole-dipole forces. These weak dipole-dipole forces allow the crystals to These weak dipole-dipole forces allow the crystals to soften when heated. These softened polymers can be soften when heated. These softened polymers can be molded or extruded into other shapes. Therefore, molded or extruded into other shapes. Therefore, linear and branched polymers are often called linear and branched polymers are often called thermoplasticsthermoplastics. Polyethylene (an addition polymer) . Polyethylene (an addition polymer) and nylon (a condensation polymer) are and nylon (a condensation polymer) are thermoplastics.thermoplastics.

PROBLEMS WITH PLASTICSPROBLEMS WITH PLASTICS

• PLASTICIZERS AND HEALTH: Plasticizers are often added to PLASTICIZERS AND HEALTH: Plasticizers are often added to synthetic polymers to make the final product soft and pliable. If synthetic polymers to make the final product soft and pliable. If plasticizers are not added, these products would be hard, brittle, and plasticizers are not added, these products would be hard, brittle, and useless for many purposes.useless for many purposes.

• Similarly, the National Institutes of Health (NIH) reports that PVC Similarly, the National Institutes of Health (NIH) reports that PVC flooring in bedrooms is associated with asthma and allergies in flooring in bedrooms is associated with asthma and allergies in children.children.

• The Food and Drug Administration (FDA) The Food and Drug Administration (FDA) has warned that the plasticizer di(2-has warned that the plasticizer di(2-ethylhexyl)phthalate (DEHP) produces “a ethylhexyl)phthalate (DEHP) produces “a range of adverse effects in laboratory range of adverse effects in laboratory animals” and might cause “adverse animals” and might cause “adverse events in humans”. The FDA has further events in humans”. The FDA has further warned that DEHP is released from warned that DEHP is released from polyvinyl chloride (PVC) medical devices, polyvinyl chloride (PVC) medical devices, including intravenous (IV) bags, blood including intravenous (IV) bags, blood storage bags, feeding bags, dialysis bags, storage bags, feeding bags, dialysis bags, catheters, and various tubing.catheters, and various tubing.

PROBLEMS WITH PLASTICSPROBLEMS WITH PLASTICS

• DISPOSAL: Plastics do not corrode, do not rust, and last DISPOSAL: Plastics do not corrode, do not rust, and last almost indefinitely. Unfortunately, these desirable almost indefinitely. Unfortunately, these desirable properties are a problem when plastics are thrown away. properties are a problem when plastics are thrown away. They do not biodegrade.They do not biodegrade.

• Thermoset plastics cannot be recycled by resoftening and Thermoset plastics cannot be recycled by resoftening and remolding. Therefore, they should not be used for remolding. Therefore, they should not be used for “disposable goods”.“disposable goods”.

• Fortunately, most plastic wastes Fortunately, most plastic wastes are recyclable. Plastic wastes are are recyclable. Plastic wastes are about 85% polyethylene, about 85% polyethylene, polypropylene, polystyrene, and polypropylene, polystyrene, and polyvinylchloride. These are all polyvinylchloride. These are all thermoplastics and can be thermoplastics and can be resoftened and remolded into new resoftened and remolded into new goods.goods.

PROBLEMS WITH PLASTICSPROBLEMS WITH PLASTICS

• FIRE HAZARDS: Toxic gases are sometimes FIRE HAZARDS: Toxic gases are sometimes released when plastics burn. For example, released when plastics burn. For example, hydrogen cyanide (HCN) is released when hydrogen cyanide (HCN) is released when polyacrylonitriles burn. And hydrogen chloride polyacrylonitriles burn. And hydrogen chloride (HCl) is released when polyvinylchloride (PVC) (HCl) is released when polyvinylchloride (PVC) burns.burns.

PROBLEMS WITH PLASTICSPROBLEMS WITH PLASTICS

• DEPENDENCE ON FOSSIL FUELS: DEPENDENCE ON FOSSIL FUELS: Plastics use fossil fuels as a raw Plastics use fossil fuels as a raw material and as a source of energy for material and as a source of energy for manufacturing. Unfortunately, fossil manufacturing. Unfortunately, fossil fuels are nonrenewable and will one day fuels are nonrenewable and will one day be gone.be gone.

SAFETYSAFETY

• Give at least 1 safety concern for the following procedures Give at least 1 safety concern for the following procedures that will be used in today’s experiment.that will be used in today’s experiment.

• Using 20 % NaOH, 5 % aqueous hexamethylene diamine, 5 Using 20 % NaOH, 5 % aqueous hexamethylene diamine, 5 % sebacoly chloride in cyclohexane, 4 % polyvinyl alcohol, % sebacoly chloride in cyclohexane, 4 % polyvinyl alcohol, 4 % borax solution, sodium silicate (water glass), and 1-4 % borax solution, sodium silicate (water glass), and 1-propanol.propanol.

• These are irritants. Wear your goggles at all times. These are irritants. Wear your goggles at all times. Immediately clean all spills. If you do get either of these in Immediately clean all spills. If you do get either of these in your eye, immediately flush with water.your eye, immediately flush with water.

• In addition, many of these reagents are flammable.In addition, many of these reagents are flammable.• Finally, you must wear protective gloves at all times.Finally, you must wear protective gloves at all times.• Your laboratory manual has an extensive list of safety Your laboratory manual has an extensive list of safety

procedures. Read and understand this section.procedures. Read and understand this section.• Ask your instructor if you ever have any questions about Ask your instructor if you ever have any questions about

safety.safety.

SOURCESSOURCES

• Advameg Inc. 2006. Intravenous Rehydration - Definition, Purpose, Description, Risks, Advameg Inc. 2006. Intravenous Rehydration - Definition, Purpose, Description, Risks, Parental Concerns. Parental Concerns. http://www.healthofchildren.com/I-K/Intravenous-Rehydration.html Available: [accessed 3 February 2007].Available: [accessed 3 February 2007].

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• Environmental Health Perspectives. 2004. Children’s Exposure to Common Plasticizers Environmental Health Perspectives. 2004. Children’s Exposure to Common Plasticizers Linked to Increased Risk of Asthma, Allergies. http://www.ehponline.org/092404a.html Linked to Increased Risk of Asthma, Allergies. http://www.ehponline.org/092404a.html Available: [accessed 3 February 2007].Available: [accessed 3 February 2007].

• Food and Drug Administration. 2002. FDA Public Health Notification: PVC Devices Food and Drug Administration. 2002. FDA Public Health Notification: PVC Devices Containing the Plasticizer DEHP. http://www.fda.gov/cdrh/safety/dehp.html Available: Containing the Plasticizer DEHP. http://www.fda.gov/cdrh/safety/dehp.html Available: [accessed 3 February 2007].[accessed 3 February 2007].

• Morrison, RT, RN Boyd. 1983. Organic Chemistry, 4th ed. Boston, MA: Allyn and Bacon, Morrison, RT, RN Boyd. 1983. Organic Chemistry, 4th ed. Boston, MA: Allyn and Bacon, Inc.Inc.

• Pavia, DL, GM Lampman, GS Kriz. Introduction to Organic Laboratory Techniques, 2nd Pavia, DL, GM Lampman, GS Kriz. Introduction to Organic Laboratory Techniques, 2nd ed. New York, NY: Saunders College Publishing.ed. New York, NY: Saunders College Publishing.

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• Tro, NJ. 2008. Chemistry, A Molecular Approach. Upper Saddle River, NJ: Prentice Hall.Tro, NJ. 2008. Chemistry, A Molecular Approach. Upper Saddle River, NJ: Prentice Hall.• U.S. Department of Energy. 2006. ITP Petroleum Refining: Petroleum Refining Industry U.S. Department of Energy. 2006. ITP Petroleum Refining: Petroleum Refining Industry

Profile. http://www.eere.energy.gov/industry/petroleum_refining/profile.html Available: Profile. http://www.eere.energy.gov/industry/petroleum_refining/profile.html Available: [accessed 3 February 2007].[accessed 3 February 2007].