1. Polymers RET LESSON MR. Groff Marlington High School

2. What is a polymer? Lets see if you know! What is a polymer? Do you use any in every day life? What are they made of?

3. LARGE MOLECULES POLYMER: A Large Molecule made up of many repeating subunits!!! http://www.youtube.com/watch?v=8b_3T7Ss4_M What are the repeating subunits called? What every day item can we compare these large molecules to?

4. Common Polymer Types Plastics!Rubber! Glass ! http://en.wikipedia.org/wiki/Polyethylene_terephthalate#mediaview er/File:Plastic_bottle.jpg http://commons.wikimedia.org/wiki/File:Reading-Glasses.jpg

5. PDMS ---polymer “Polydimethylsiloxane” Picture from ref. 2.

6. How we will make it Silicone Base + Curing Agent (cross linker)+ Heating (crosslinking catalyst) Then we have cross-linked material! Now, if we want a certain thickness, and we are going to make it in glass petri dishes…how will we know how much to use……???

7. DENSITY=Mass/Volume D PDMS= 965.00 kg/m³ What variables from the Density Formula do we need…? Lets break them down 1. Volume First---Thickness 2. Mass 2 nd for CRL Ratio

8. Entropy and Potential Energy. What causes certain materials to return after being stretched? Why do rubber bands “go back”? These questions can be answered through a simple understanding of ENTROPY. ENTROPY: a measure of molecular disorder. Through altering a material, by cross-linking it for example, one can give order to the disorder. This can cause properties such as elasticity. By stretching an elastic polymer you can cause the entropic spring result and amounts to saying: upon stretching a polymer chain you are doing work on the system, thereby increasing its potential energy due to dragging it away from its (preferred) equilibrium state. An example of this is a common elastic band, composed of long chain (rubber) polymers

9. Visual-crosslinking (A) is an unstressed polymer; (B) is the same polymer under stress. When the stress is removed, it will return to the A configuration. (The dots represent cross- links) Force Applied Entropic Spring Result (restoring force) Picture from ref. 3

10. Young’s Modulus STRESS vs. STRAIN Stress—The Internal Force per unit area associated with a strain. Strain–- The Relative change in shape or size of an object due to externally applied forces. Stress/Strain=Young’s Modulus.

11. Visual Area= (x)(z) x zL L ΔL Force Applied Entropic Spring Result (restoring force)

12. Young’s Cont. Stress = (Force/Cross sectional area) Strain= (Change in Length/ Initial Length) E= Young’s Modulus Equation from ref. 4.

13. Stress Strain and Hooke’s Law Picture from ref 6. Picture from ref 5.

14. CHOOSE!!!! Young’s Modulus due to CRL Ratio 20:1 or 10:1 or 8:1 Young’s Modulus due to Thickness of Sample 1mm2mm4mm

15. Bibliography 1. Polymer physics. (2014, July 7). In Wikipedia, The Free Encyclopedia. Retrieved 14:21, July 14, 2014, from http://en.wikipedia.org/w/index.php?title=Polymer_physics&oldid=615926552 http://en.wikipedia.org/w/index.php?title=Polymer_physics&oldid=615926552 2. Polydimethylsiloxane. (2014, June 27). In Wikipedia, The Free Encyclopedia. Retrieved 14:22, July 14, 2014, from http://en.wikipedia.org/w/index.php?title=Polydimethylsiloxane&oldid=614644275 http://en.wikipedia.org/w/index.php?title=Polydimethylsiloxane&oldid=614644275 3. Elastomer. (2014, May 13). In Wikipedia, The Free Encyclopedia. Retrieved 14:30, July 14, 2014, from http://en.wikipedia.org/w/index.php?title=Elastomer&oldid=608353943 http://en.wikipedia.org/w/index.php?title=Elastomer&oldid=608353943 4. Young's modulus. (2014, June 26). In Wikipedia, The Free Encyclopedia. Retrieved 14:46, July 14, 2014, from http://en.wikipedia.org/w/index.php?title=Young%27s_modulus&oldid=614521775 http://en.wikipedia.org/w/index.php?title=Young%27s_modulus&oldid=614521775 5. Stress–strain curve. (2014, July 5). In Wikipedia, The Free Encyclopedia. Retrieved 14:49, July 14, 2014, from http://en.wikipedia.org/w/index.php?title=Stress%E2%80%93strain_curve&oldid=615693329 http://en.wikipedia.org/w/index.php?title=Stress%E2%80%93strain_curve&oldid=615693329 6. Hooke's law. (2014, July 9). In Wikipedia, The Free Encyclopedia. Retrieved 15:00, July 14, 2014, from http://en.wikipedia.org/w/index.php?title=Hooke%27s_law&oldid=616204891 http://en.wikipedia.org/w/index.php?title=Hooke%27s_law&oldid=616204891