Natural and Synthetic Polymers - EK - annotated.pdf

Natural and Synthetic Polymers 1 Almost everything that we use are made up of polymers Polymers A polymer is a high molar mass molecular compound made up of many repeating chemical units. Proteins Naturally Nucleic Acids occurrin...

Natural and Synthetic Polymers 1 Almost everything that we use are made up of polymers Polymers A polymer is a high molar mass molecular compound made up of many repeating chemical units. Proteins Naturally Nucleic Acids occurring Cellulose Rubber Nylon Synthetic Dacron Lucite Monomers The simple repeating unit of a polymer is the monomer.  Proteins Proteins are polymers of amino acids Play a key role in nearly all biological processes Enzymes, the catalysts of biochemical reactions Transport of materials Storage of vital substances Coordinated motion Mechanical support Protection against diseases Amino Acids Amino acids are joined in a protein by the formation of a peptide bond Peptide (amide) bond List of Essential Amino Acids Sickle Cell Anemia: A Molecular Disease nonpolar portion of valine Nucleic Acids Nucleic acids are high molar mass polymers that play an essential role in protein synthesis. Deoxyribonucleic acid (DNA) Ribonucleic acid (RNA) DNA molecule has 2 helical strands. Each strand is made up of nucleotides. The Components of the Nucleic Acids DNA and RNA Natural Polymers Exist in living things (found both in plants and animals) Hair is a polymer made up of keratin Natural Polymers Wood and grass have cellulose Natural Polymers Cotton Natural Polymers Vulcanization: Properties of Rubber sulfur cross-links before vulcanization after vulcanization stretched relaxation after stretching Synthetic Polymers Originally intended to replace or substitute expensive or rare natural polymers Man-made Sometimes called plastics, a term that applies to materials with a broad range of properties and applications Hydrocarbons: The Backbone of Most Polymers Many common classes of polymers are composed of hydrocarbons. Carbon makes up the backbone of the molecule and hydrogen atoms are bonded to the carbon atoms. Functional Groups Functional groups are distinctive arrangements of groups of atoms that impart characteristic chemical properties to the molecules that contain them. Monomer Similarities The molecular structures of the monomers are very similar, varying by only a single functional group in their monomers:  R groups on same side of chain Stereoisomers Isotactic of Polymers R groups alternate from side to side Syndiotactic R groups disposed at random Atactic Crystallinity Polymers may have regions of crystallinity, while other parts will have amorphous regions Crystalline regions impart strength and abrasion resistance (found in high-density polyethylene and polyethylene). Polymerization: Addition Reactions Involve unsaturated compounds containing double or triple bonds Particularly C=C and C≡C  Mechanism of Addition Polymerization initiator repeating unit (monomer) Homopolymer A polymer made up of only one type of monomer ( CH2 CH2 )n ( CF2 CF2 )n ( CH2 CH )n Polyethylene Teflon Cl PVC Copolymers A polymer made up of two or more monomers Styrene-butadiene rubber  Polymerization: Condensation Reactions Polymers crosslink together by eliminating a small molecule, such as water. Some Monomers and Their Common Polymers Nylon Polymer branching Two Types of Polyethylene High density polyethylene (HDPE) exists as mostly linear molecules that pack closely together. It is used for milk jugs, bottle caps, toys, etc. Two Types of Polyethylene Low density polyethylene (LDPE) is a more highly branched form of polyethylene. It is used to make plastic bags, plastic films, electric wire insulation, etc. Which of these bottles is made of HDPE and which of LDPE? Two bottles, both made of polyethylene, were heated in the same oven 1 for the same length of time 2 The BIG SIX Polymers The BIG SIX Polymers Polyethylene terephthalate (PET) Copolymers: ethylene glycol and terephthalic acid Commonly used in beverage bottles because of its semi-rigidity, colorless, and gas tight properties Recyclable but not reusable  Polyesters When an ester functional group connects the monomers, it is referred to as a polyester (used in clothing fabrics). One example is polyethylene terephthalate, PET: High Density Polyethylene (HDPE) Stiff plastic used to make milk jugs, detergents, oil bottles, toys, some plastic bags One of the safest forms of plastic Hard-wearing Reusable and recyclable  Polyvinyl Chloride (PVC) PVC can be further softened with plasticizers, compounds that are added in small amounts to polymers to make them softer and more pliable “poison plastic” Less than 1% of PVC materials are recycled Low Density Polyethylene (LDPE) Less toxic compared to other plastics Not commonly recycled When recycled, LDPE is not as hard as recycled HDPE. Reusable, but not always recyclable Polypropylene (PP) From propylene, common name of propene strong, tough, lightweight, and able to withstand high temperatures Serves as a barrier against moisture, grease, and chemicals Used for diapers, pails, plastic bottle tops, potato chip bags, yogurt containers, plastic washable bottles Recyclable and reusable  Polystyrene (PS) Naturally transparent thermoplastic that is available as both a typical solid plastic as well in the form of a rigid foam material Breaks up easily and is dispersed throughout the natural environment May leach styrene to food, a possible human carcinogen Recycling is not widely available; market for recycling is small  The Four Rs Reduce the amount of materials used; for instance, use less plastic in the production of a bottle Reuse materials; for instance, use you own bags at the grocery store Recycle materials; that is, don’t throw beverage bottles away Recover either the materials or the energy content from materials that cannot be recycled. For instance, burn unrecyclable plastics that contain a high-energy content https://supersimple.com/article/plastic-bottle-planters/ https://www.positive.news/environment/norway-recycles-97-of-its-plastic-bottles-a-blueprint-for- https://www.greenmatters.com/news/2017/10/30/zfh5a/edible-water- the-rest-of-the-world/ bottle-plastic-pollution https://www.forbes.com/sites/trevornace/2019/03/25/thailand-supermarket-uses- banana-leaves-instead-of-plastic-packaging/#19069aa37102 Landfills Modern waste disposal facilities are covered and lined to deter leaching of waste and waste by- products into the surrounding ground https://www.newhope.com/news/55-recycled-waste-clogs-landfills-plant-based-butter-wars Composition of Municipal Solid Waste Recycling Plastics Only 3.5% of plastic in the U.S. is recycled. Some polymers, such as those in plastic bottles, are heavily recycled, whereas others are almost never recycled. Plastic Amount Recycled in 2013 Recycling Rate Polypropylene (PP) 62.0 31.8% High-density polyethylene 1045 31.6% (HDPE) Polyethylene terephthalate 1798 31.2% (PET) Polyvinyl chloride (PVC) 0.4 0.5% Low-density polyethylene 0.3 0.4% (LDPE) Cradle-to- Cradle Recycling Plastics from Renewable Materials Polymers originating from renewable sources such as wood, cotton, fibers, starch, or sugar are different from petroleum-based polymers: They are compostable; they are able to undergo biological decomposition to form a material that contains no toxic substances. Their synthesis involves fewer resources, results in less waste, and uses less energy. They do not contain chlorine or fluorine. Some polymers can be converted back into monomers and remade into virgin polymer. Polylactic Acid (PLA): A Common Renewable Polymer Polylactic acid (PLA) is a thermoelastic polyester, which has a similar look and feel to polyethylene terephthalate (PET). PLA softens at 140 C, as compared to >250 C for PET. Its monomer is lactic acid, which contains carboxylic acid and hydroxyl functional groups: