Polymers

Latin: Plasticus, that which can be molded Polymer This name hints at how polymers are made Many + Parts PLASTICS Latin: Plasticus, that which can be molded

Styrene-butadiene or rubber If a Monomer = A then a Homopolymer = A-A-A-A-A-A-A-A- And a Copolymer = A-B-A-B-A-B-A-B-A Ex: Addition Polymerization- same monomers C=C + C=C + C=C    -C-C-C-C-C-C- monomer monomer monomer homopolymer Ex: Addition Polymerization (Copolymer) Different monomers ( CH CH2 CH2 CH CH CH2 )n Styrene-butadiene or rubber 25.2

The simple repeating unit of a polymer is the monomer. Homopolymer made up of only one type of monomer. ( CF2 CF2 )n Teflon ( CH2 CH2 )n Polyethylene ( CH2 CH )n Cl PVC

Copolymer Terylene Made up of two different monomers benzene-1,4-dicarboxylic acid Old name: terephthalate ethane-1,2-diol Esterification PET (Polyethylene terephthalate) – used to made plastic soda bottles

Condensation polymers 10/04/2019 POLYMER REACTIONS Addition polymers Condensation polymers long chain from monomers AND no other products long chain molecules from monomers AND another small molecule product (e.g. water)

Addition Polymer of Ethene

POLYMERISATION OF ALKENES ADDITION POLYMERISATION The equation shows the original monomer and the repeating unit in the polymer ethene poly(ethene) MONOMER POLYMER n represents a large number

Free Radical Polymerization (3 minute clip) https://www.youtube.com/watch?v=0yOJajPJptA

Free radical mechanism 3 stages: Initiation Propagation Termination THE MECHANISM OF ADDITION POLYMERISATION https://www.youtube.com/watch?time_continue=1&v=0yOJajPJptA Free radical mechanism 3 stages: Initiation Propagation Termination

ADDITION POLYMERIZATION Initiation: An ether is cleaves (cut) in half using heat. Now we have the crazy 1 e-. 1 e- or a single or an unpaired electron is VERY reactive. Free Radical Another Free Radical REACTIVE (Ether)

ADDITION POLYMERIZATION Propagation: Free radicals from the first step starts the addition process

ADDITION POLYMERIZATION Termination: Two radicals react and deactivate themselves

Summary of Free Radical Polymerization

STOPPING POLYMERIZATION REACTIONS How can the polymerization reaction end or be stopped? Run out or reactants (monomers) ii) 2 free radial monomers combine head to head 2 ways

Sterioisomers ISOTACTIC SYNDIOTACTIC ATACTIC CH3 groups on same side CH3 groups alternate sided ATACTIC random

BRANCHING CHAINS STRAIGHT CHAINS Low density poly(ethene) LDPE 200C, 2000 atm, O2 Molecules loosely packed due to branching Flexible & soft Bags, cling flim BRANCHING CHAINS High density poly(ethene) HDPE 60C, 2 atm, Catalyst: Ziegla-Natta TiCl3 and Al(C2H5)3 Molecules tightly packed Stiffer & harder Buckets, bottles STRAIGHT CHAINS

Polyethylene 1) HDPE, called high density polyethylene, with straight chains. It is hard and molecules tightly packed, lots of intermolecular forces holding. Ex: Buckets 2) LDPE has many branching chains . It is soft, Ex: “cling wrap”

Polymerisation of Ethene https://www.youtube.com/watch?v=sk6h4oaArE0

DIFFERENT KINDS OF PLASTIC EXAMPLES OF ADDITION POLYMERISATION ETHENE POLY(ETHENE) PROPENE POLY(PROPENE) CHLOROETHENE POLY(CHLOROETHENE) POLYVINYLCHLORIDE PVC TETRAFLUOROETHENE POLY(TETRAFLUOROETHENE) PTFE “Teflon”

PVC Every other hydrogen is replaced with a chlorine atom

PVC Addition

PVC

Other Addition Products Ex: PTFE / Teflon

Polystyrene

POLYMERISATION OF ALKENES SPOTTING THE MONOMER

POLYMERISATION OF ALKENES SPOTTING THE MONOMER

Polymerisation of Propene https://www.youtube.com/watch?v=nz1ucI6gCIg

poly(propene)

Cellulose made of chains of the sugars POLYMERS Large molecules (macromolecules) madefrom monomers. Natural polymers Protein, cellulose Synthetic polymers Polyethylene, poly (vinyl chloride) polystyrene, etc….. NATURAL POLYMER Cellulose made of chains of the sugars Homopolymer Copolymer

Thermosoftening v Thermoset https://www.youtube.com/watch?v=rhFc477fs6s

ADDITION POLYMERISATION Chemical Properties Fairly inert. Why do plastics melt but not react? 2) Biodegradability Addition polymers do NOT break down Condensation polymers DO, why? Answer:Nu can attack the polar bonds; i.e. C-N and C-O bonds which link every polymer unit and as a result the polymers can be broken The carbon–carbon covalent chemical bonds are strong so they do not break and react. But weak forces responsible for the physical properties and plastics should melt a very low temperatures, but here are many, thousands of these atoms, so plastics melt but at reasonably high temperatures Ex: 150 0C (polyethene), like butter does.

Chemsheets AS006 (Electron arrangement) 10/04/2019 POLYESTERS

e.g. terylene (PET)

Polyesters e.g. terylene (PET) ethane-1,2-diol benzene-1,4- dicarboxylic acid repeating unit polymer structure

dicarboxylic acid diol –H2O

Dicarboxylic acid + diol Polyesters Dicarboxylic acid + diol – H2O –H2O repeating unit polymer structure

Chemsheets AS006 (Electron arrangement) 10/04/2019 POLYAMIDES

e.g. Kevlar

2 Condensation Reactions Amidification Esterification

Polyamides e.g. nylon-6,6 1,6-diaminohexane hexane-1,6-dioic acid repeating unit polymer structure Note: The Cambridge Exam asks for repeating unit it is the polymer WITHOUT the brackets

Polyamides Ex : 2 e.g. Kevlar 1,4-diaminobenzene benzene-1,4- dicarboxylic acid repeating unit polymer structure

dicarboxylic acid diamine –H2O

Dicarboxylic acid + diamine Polyamides Dicarboxylic acid + diamine –H2O polymer polymer structure Short hand repeating unit

Amino acids join together via an amide or peptide link PEPTIDES Reagents amino acids Equation H2NCCH2COOH + H2NC(CH3)COOH ——> H2NCCH2CONHHC(CH3)COOH + H2O Product peptide (the above shows the formation of a dipeptide) Eliminated water Mechanism addition-elimination Amino acids join together via an amide or peptide link 2 amino acids joined dipeptide 3 amino acids joined tripeptide many amino acids joined polypeptide a dipeptide

contains both acid + amine group Amino acids (Polyamides) POLYMER MONOMER repeating unit contains both acid + amine group polymer structure

HYDROLYSIS OF PEPTIDES + HOH (water) HOOCCH2NH2 + HOOCCH(CH3)NH2 Acid hydrolysis The acid groups remain as they are and the amine groups are protonated

PROTEINS • polypeptides with large relative molecular masses (>10000) • chains can be lined up with each other • the C=O and N-H bonds are polar due to a difference in electronegativity • hydrogen bonding exists between chains dotted lines ---------- represent hydrogen bonding

Plastic can be bad

Plastics Uses and Problems https://www.youtube.com/watch?v=eZiBAkbCR0E

Disadvantages of Plastic Most plastics are non-biodegradable. 2) Plastics are made from fossil fuels which are non-renewable 3) During combustion toxic fumes are released. Combustion and toxic fumes (CH2CHCl)n + O2  CO2 + CO + HCl + H2O The chlorines in the PVC combine with the hydrogen atoms to form hydrogen chloride gas (HCl). When this contacts water in lungs or mouth, it turns to hydrochloric acid (HCl(aq)).

They are cheap and easy to make. They don’t oxidize (rust). Advantages of Plastics They are cheap and easy to make. They don’t oxidize (rust). Plastics are resistant to chemical attack They are easy to mould into shape and colour They last a lot longer than many metals   .

Biodegradable Plastics Instead of using fossil fuel derived monomers for polymerization, Starch from foods (corn starch or potato starch can be used, they can polymerize and form plastics as well as ethene or propene. Advantage: pollution control as these will rot in less than a year Disadvantage: using food when the world still has hungry people is grossly unethical. These plastics do not work as well

Boardworks GCSE Science: Chemistry Making Polymers How much waste plastic? https://www.youtube.com/watch?v=_6xlNyWPpB8 (5 minutes) There are three ways to dispose of waste plastics: landfill incineration (burning) recycling Each has its own advantages and disadvantages. Photo credit: University of Oklahoma Physical Plant

Landfill Disposal of Polymers 1 Advantages Disadvantages Cambridge Question : Addition polymers are non-biodegradable but ccondensation polymers can degrade, why the difference? Answer :Nu can attack the polar bonds; i.e. C-N and C-O bonds which link every polymer unit and as a result the polymers can be broken Landfill Advantages Disadvantages No sorting costs Modern landfills do not pollute. Plastics break down to make methane which can generate electricity. Distance to landfill sites so transport costs. If too much methane builds up, explosions can occur.

Incineration (burning) Disposal of Polymers 2 Incineration (burning) Advantages Disadvantages Burning plastics produces heat energy. Polythene produces more energy than burning coal or oil. Saves fossil fuels Burning at low temperatures can produce harmful dioxins Old incinerators (low temperature) produce harmful gases.

Recycling Disposal of Polymers 3 Advantages Disadvantages Plastic is lightweight even when compressed. Cheaper to recycle plastics than make then from scratch. Recycled plastics can be used to make lots of useful materials Some plastics can be broken down to make raw materials for other products. Plastics must be collected and sorted. Many plastics contain materials that need to be removed. Cost of transporting to nearest recycling plant. Recycled materials are weaker

Plastics How They are Made https://www.youtube.com/watch?v=JararyOXa0Q

Quiz http://www.bbc.co.uk/education/guides/zxm39j6/activity