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Department of Chemistry CHEM1020 General Chemistry *********************************************** Instructor: Dr. Hong Zhang Foster Hall, Room 221 Tel:

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Presentation on theme: "Department of Chemistry CHEM1020 General Chemistry *********************************************** Instructor: Dr. Hong Zhang Foster Hall, Room 221 Tel:"— Presentation transcript:

1 Department of Chemistry CHEM1020 General Chemistry *********************************************** Instructor: Dr. Hong Zhang Foster Hall, Room 221 Tel:

2 CHEM1020/General Chemistry _________________________________________ Chapter 10. (L8)-Organic Chemistry Today’s Outline..From bricks to walls, from small molecules to giant molecules, from monomers to polymers..Natural polymers..Celluloid..Polyethylene

3 Chapter 10. (L8)-Organic Chemistry Polymers all around us Polymers are present all around us in our life. Wherever you have plastics, most likely, you have polymers. Polymers: Essential materials in our life Examples: cars, building, clothes, stationary, PC, TV, the list can go on and on…… Artificially made polymers Natural polymers: Many biochemical molecules are polymers (learn more later on)

4 Chapter 10. (L8)-Organic Chemistry Polymerization: From bricks to walls..Polymers are macromolecules...A polymer is made from monomers, small molecular units...In chapter 9, we learned a lot about various kinds of “small” organic molecules and many of them can form polymers...Polymerization: The process by which monomers are converted to polymers...A polymer is different physically and chemically from the monomers that make up the polymers.

5 Chapter 10. (L8)-Organic Chemistry Natural polymers …Examples of natural polymers: starches/  -glucose, C 6 H 12 O 6, proteins/amino acids wood/cellulose cotton/cellulose cellulose/  -glucose silk and wool/proteins DNA/RNA chains

6 Chapter 10. (L8)-Organic Chemistry Celluloid: Artificial polymers, something we learned from the nature …Celluloid: a synthetic material by chemical modification of natural macromolecules: Celluloid is composed of cellulose nitrate: cellulose treated with nitric acid (HNO 3 )

7 Chapter 10. (L8)-Organic Chemistry Celluloid: Artificial polymers, something we learned from the nature …Celluloid: Billiard balls John Wesley Hyatt ( ) found a way to soften cellulose nitrate by treatment of ethyl alcohol (ethanol) and camphor; the softened material can be molded to make smooth, hard billiard balls to replace those made of ivory.

8 Chapter 10. (L8)-Organic Chemistry Celluloid: Artificial polymers, something we learned from the nature …Celluloid: Movie film and stiff collar The movie industry used to be called “the celluloid industry” Celluloid is dangerously flammable, so it was replaced now with safer substitute such as cellulose acetate, a semisynthetic modification of natural cellulose.

9 Chapter 10. (L8)-Organic Chemistry Polyethylene: A simple polymer of complicated applications …Polyethylene: One of the most prevalent plastics Examples of its uses: plastic bags, and various kinds of bags …Polyethylene was invented shortly before WWII and was right away used then and made a difference (see book on pp.279)

10 Chapter 10. (L8)-Organic Chemistry Polyethylene: A simple polymer of complicated applications …Polyethylene: Made of monomers of the units from ethylene: CH 2 =CH 2 n(CH 2 =CH 2 )  (~CH 2 -CH 2 ~) n (n = ) Thus, in a sense, polyethylene is actually a giant alkane molecule with simple C-C bonding.

11 Chapter 10. (L8)-Organic Chemistry Polyethylene: A simple polymer of complicated applications …Two types of modern polyethylene polymers: HDPEs, High-density polyethylene, mostly linear molecules packed close together with a fairly ordered crystalline structure; rigid, good tensile strength. Widely used for threaded bottle caps, toys, bottles, gallon milk jugs

12 Chapter 10. (L8)-Organic Chemistry Polyethylene: A simple polymer of complicated applications …Two types of modern polyethylene polymers: LDPEs, Low-density polyethylene, a lot of side chains, which makes close packing together difficult and discourages the crystalline structures. LDPEs are waxy, bendable plastics, and easily to become deformed in hot water. Widely used to make plastic bags and films, squeeze bottles, electric wire insulation, and many common household products.

13 Chapter 10. (L8)-Organic Chemistry Thermoplastic and thermosetting polymers …A thermoplastic polymer can be softened by heat and pressure and then reshaped. It can be repeatedly melted down and remolded. Thermoplastics an be reshaped because their linear or branched molecules can slide past one another when heat and pressure are applied. Total production in USA in 2001: 32 billion kg, among that, 13 billion kg was polyethylene.

14 Chapter 10. (L8)-Organic Chemistry Thermoplastic and thermosetting polymers …A thermosetting polymer is the material that harden permanently when formed. It cannot be softened by heat and remolded. Strongly heating will lead to its discoloring and decomposition. The properties of thermosetting plastics are caused by cross-linking of polymer chains.

15 Chapter 10. (L8)-Organic Chemistry Fullerenes and nanotubes and nanomaterials (book, pp. 280) …Fullerenes …Nanotubes and nanomaterials …A nanoage?

16 Chapter 10. (L8)-Organic Chemistry Quiz Time Homework (due Wed next week): Make up three quiz questions based on this lecture, each with four choices and one being the right answer. (My quiz questions for practice will be available Wed. next week also)

17 Chapter 10. (L8)-Organic Chemistry Quiz Time In polymer chemistry, a polymer is made of a basic organic molecular unit called (a) brick; (b) chip; (c) monomer; (d) slice.

18 Chapter 10. (L8)-Organic Chemistry Quiz Time Which of the following are natural polymers (a) Al foil; (b) air; (c) starch, proteins, wool, silk, cotton; (d) steal bar.

19 Chapter 10. (L8)-Organic Chemistry Quiz Time Polyethylene is a polymer made of the monomer of (a) ethane; (b) ethylene; (c) acetate; (d) ethanol.

20 Chapter 10. (L8)-Organic Chemistry Quiz Time The bonding between two carbon atoms in polyethylene is (a) triple bond; (b) double bond; (c) single bond; (d) none of above is right.

21 Chapter 10. (L8)-Organic Chemistry Quiz Time In polymer chemistry, HDPE means (a) high dose pizza eater; (b) hopelessly dangerously polluted earth ; (c) high density polyethylene; (d) historical diamond pop event. The same for LDPE


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