“The World We Create” NATS 101 Section 6 Next Homework To be posted in D2L today! 03/25 1

UNIT 3: New Materials, To Build or to Waste?

What is ONE thing they all have in common??? All of them are made of POLYMERS!

PolymersPolymersPolymersPolymersPolymersPolymersPolymers Can you identify all of the things made of polymers (plastics, fibers) that allow this game to be played?

Our Focus: Polymers What is a polymer? What are polymers made of? How do the sub-units connect, and how do polymers align themselves? How do polymer structure determine its properties? Understanding their chemistry can help us use them wisely!

PolymersPolymersPolymers Polymers are made by very large molecules made up from many smaller molecules joined together. “mono” = single (individual) “poly” = many “mer” = part Most polymers are made up of one or two different types of monomers.

How the Monomers become Polymers? Chemical bonds are formed between monomers, and a NEW PRODUCT IS MADE. Demo: Synthesis of Nylon

Polymer Properties The properties of a polymer depend on two main factors: Chemical composition of the monomers; Geometry of the polymer chains;

Let’s Explore Some Polymers! Identify some physical properties of the polymeric materials in your bag PROPERTIES: flexibility, elasticity, density etc. Try to group the materials into 3 different groups according to “similar” properties. You Have 15 minutes 9

Let’s Explore Some Polymers! Some properties to consider: Materials Properties Some properties to consider: Density Flexibility Elasticity Stretchable Hardness A Styrofoam, Plastic bottle, Party cups Somewhat Dense Flexible Semi-stretchable B Rubber band Pantyhose Socks Low density Somewhat Elastic Stretchable C PVC pipe Pen caps Wood dowels Very Dense Hard Brittle 10

Three Main Structures Linear chains Branched chains Which of these polymer structures would lead to a more or less dense plastic? Branched chains Cross-Linked chains

Let’s talk more about Structure Properties How are the properties of a polymer related to its structure? 12

Linear Structure Due to minimal branching, the linear polymer molecules can pack tightly, resulting in a strong, rigid structure known as a high density polymer. 13

Linear Structure: Example polymerizes The first commercially produced polymer is also the simplest and most common: polyethylene, meaning it is a polymer made from the monomer, ethylene. Ethylene is a small molecule containing two carbon atoms linked by a double bond and four hydrogen atoms, two bonded to each carbon. It is the most widely used plastic, with an annual production of approximately 80 million metric tons. The properties of this type of polymer depend on the regularity of the arrangement of the chains. If they are lined up in a regular way, they are strong, hard materials. If they are more irregular, or there are more side-chains on the molecules, they are more flexible. It is used to make plastic lumber, milk jugs, detergent bottles, garden furniture, flowerpots, trash cans, folding chairs, signs and more. HDPE has a low degree of branching, giving it stronger intermolecular forces and tensile strength (does not deform as easily) than lower-density polyethylene. Its monomer is (C2H4) High Density

Linear Structure: Example Nature has many examples of polymers. Cotton fibers are made of sugar molecules that are repeated in a chain-like manner. Hair, wool, and other natural fibers are polymers. They are made by chaining one or two substances one after another. It is used to make paper, paperboard, card stock, textiles or fabrics made from cotton, linen, other plant fibers, and more. Humans can digest cellulose to some extent, however its main purpose is a dietary fiber Its monomer is (C6H10O5) 15

Branched Structure Due to higher amounts of branching (as compared to linear), the polymer structures can’t pack tightly together, resulting in a softer, more flexible polymer.

Branched Structure: Example Ethylene monomer Ethylene monomer Low Density It is used to make bags, plastic wraps, squeeze bottles, wrapping films, container lids, six-pack soda can rings, very soft and pliable parts, and more. LDPE has a high degree of short and long chain branching giving it weaker intermolecular forces and tensile strength than high density polyethylene but more elasticity. Its monomer is (C2H4) Polyethylene

Cross-Linked Structure The presence of the cross-linking bonds keeps the polymer elastic, but stronger than branched polymers (ex: Natural rubber vs. “Goodyear” tires). However, a higher concentration of cross-linking bonds can yield a somewhat brittle polymer. (ex: “Goodyear” tires vs. PVC pipe).

Cross-Linked: Example Ethylene monomer Crosslinking is often accomplished by adding substances that create chemical bonds between chains Ultra High Molecular Weight PolyEthylene (composed of 160 to 215,000 ethylene monomers)

Cross-Linked: Example A naturally occurring cross-linked polymer:

Let’s Create 3 different polymers You will be given a pack of “bendaroos” (Amazing Flexible Building Sticks) You Have 10 minutes Use them to build a model for the structure of the polymeric materials needed to produce: Water Pipes Canoes Plastic Gloves 21

Polyethylene terephthalate Other Common Polymers Polyvinyl chloride Polyethylene terephthalate Commonly abbreviated PET, it is used in carpets, rope, fabrics, synthetic fibers, scouring pads, soft drink bottles, certain food and liquid containers, Mylar tape, and more. Its monomer is (C10H8O4) It is used to make cooking oil bottles, drainage and sewer pipes, PVC pipes, tile, institutional furniture, credit cards, used in clothing to make waterproof, and more. Its monomer is (C2H3)

Other Common Polymers Polypropylene Polystyrene PP: It is used to make yogurt containers, bottles, automobile batteries, laboratory equipment, plastic parts and reusable containers of various types, office supplies, writing implements, greeting cards, glue, pencil cases, loudspeakers, automotive components, and more. Its monomer is (C3H6). PS: It is used to make disposable cups and utensils, toys, plastic models, CD and DVD cases, packing materials, insulation, foam drink cups, and more Its monomer is (C8H8)

The more similar the structure, the stronger the interactions Polymer Interactions Because of the role of water in our world, determining how polymers interact with H2O is very important. Water interacts more strongly with “water-like” substances (compounds with oxygen attached to hydrogen, for example) Polyethylene Starch Strong Weak O H C Acetone The more similar the structure, the stronger the interactions

Let’s Predict and Observe Water Consider these materials Acetone Cellulose You have 3 minutes Predict what should happen when the polymers interact with water and acetone. Polystyrene

Polymer Interactions Whether a polymer gets wet or dissolves in a liquid depends on its chemical composition and structure. PVA LAUNDRY BAGS TEFLON

Consider this scenario: If you needed to buy new tires for your vehicle and your choices were PVA or polyisoprene, which would you choose and why? OR Polyisoprene PolyVinyl Acetate

Our Focus: Polymers What is a polymer? What are polymers made of? How do the sub-units connect, and how do polymers align themselves? How do polymer structure determine its properties? Understanding their chemistry can help us use them wisely!

What have you learned? If you were asked to create a bullet proof mask, which polymer would you use to design the mask? Remember the shirt from last lecture that shrunk when hot and expanded when cold. Which types of polymers do you think were used in creating this shrinkable and impermeable shirt? If asked to create an ink pen that was bendable, but still was rigid enough to contain a water-based ink, which type of polymer would you use? As a team, write your answers on a piece of paper. a) Justify your choices based on composition and structure, and b) draw a molecular model of each material.