1. Polymers HairFurFingernailsSilkCottonPolyamides(nylons)PolyesterPolyethylenePVAPVCDacronLycra What are they all?

2. Polymers The word polymer literally means "many parts.” repeating structural units called monomers. There are both naturally occurring and synthetic polymers.

3. Mer Mer – The repeating unit in a polymer chain Monomer – A single mer unit (n=1) Polymer – Many mer-units along a chain (n=10 3 or more) Many mer-units along a chain (n=10 3 or more) Degree of Polymerization – The average number of mer-units in a chain.

4. There are both naturally occurring and synthetic polymers. Naturally occurring polymers proteinsStarches cellulose (plants) cellulose (plants)Rubber/latex.RNA/DNAcarbohydratesSyntheticPolyethylene Polyvinyl chloride Polystyrene Plastics are synthetic polymers Synthetic polymers remain in the environment for a LONG TIME

5. http://pslc.ws/mactest/level1.htm

6. Different Polymer Structures

7. Important Vocabulary Plastomer – bendable polymers Elastomers – Elastic polymers Brittle – Not flexible. Will break, not bend

8. Polymers A polymer is a long chain of molecules that look something like strands of cooked spaghetti. If the polymer chains slide past each other easily, then the substance acts like a liquid, because the molecules flow. If the molecules hook together at a few places along the strand, then the substance behaves like a rubbery solid.

10. Linear Polymer Structure Polymers that are bonded in straight lines, form long chains or cross-linked structures. Generally high Melting Point thermoplastics High Density

11. Strength Depends on Direction Tape Experiment 1.Tear tape across 2.Tear tape lengthwise Do they tear the same? Why?

12. Branched Structure Monomers branch off a polymer structure Low Density because they occupy more space

13. Why do Low Density polymers have more branches? Fewer branches allow the carbon backbones to get close together More Branches =Fewer Branches = More Branches =Fewer Branches = less mass in space more mass in space less mass in space more mass in space

14. Cross-Linked Polymer Linear polymers are linked together Either covalent or hydrogen bonds Hard, brittle, not flexible More cross-links = increase strength and stiffness

15. Entanglement When polymer chain (or chains) get tangled Think of a tangled ball of string Cold pile of spaghetti More entangled = stronger and less flexible

16. Review To increase Strength Increase # of cross-links Lots of entanglements To increase Density To increase Density Decrease # of branched Make linear structures, not branched To increase Flexibility Decrease # of branched Make linear structures, not branched Increase temperature

17. What is going on? CROSS – LINKING Borax is helping PVAs ionically bond together

18. Test your knowledge http://pslc.ws/macrog/kidsmac/activity/activity.htm