Synthetic and Biological Polymers Macromolecules formed by the
Synthetic and Biological Polymers: Macromolecules formed by the covalent attachment of a set of small molecules termed monomers. Polymers are classified as: (1) Man-made or synthetic polymers that are synthesized in the laboratory; (2) Biological polymer that are found in nature. Synthetic polymers: nylon, poly-ethylene, poly-styrene Biological polymers: DNA, proteins, carbohydrates 1
Hydrocarbons ex: Alkanes 1 – Meth 2 – Eth 3 – Prop 4 – But 5 – Pent 6 – Hex 7 – Hept 8 – Oct 9 – Non 10 – Dec 11 – Undec 12 – Dodec
Hydrocarbons at Room Temperature Gas Methane Ethane Propane Butane Liquid 5 to 19 Carbons Waxy 20 to 40 Carbons Plastic 40 or more Carbons
Melting Point As the length of hydrocarbons get longer, the Melting Point grows Higher. Why?
What other material properties change? Viscosity Hardness Toughness Flammability
Bonding Covalent Ionic (Na. Cl) Polar (H 2 O) Van der Waals
Methods for making polymers Addition polymerization and condensation polymerization Addition polymerization: monomers react to form a polymer without net loss of atoms. Most common form: free radical chain reaction of ethylenes n monomers one polymer molecule 7
Example of addition polymers 8
Free-Radical Addition. Polymerization of Ethylene H 2 C CH 2 200 °C 2000 atm CH 2 O 2 peroxides CH 2 polyethylene CH 2
Free-Radical Polymerization of Propene H 2 C CH CH CH 3 CHCH 3 CH CH CH 3 CH 3 polypropylene
. . • RO. . H 2 C Mechanism CHCH 3
. . RO: H 2 C Mechanism CHCH 3 •
. . RO: H 2 C Mechanism CHCH 3 • H 2 C CHCH 3
. . RO: H 2 C Mechanism CHCH 3 H 2 C CHCH 3 •
. . RO: H 2 C Mechanism CHCH 3 H 2 C CHCH 3 • H 2 C CHCH 3
. . RO: H 2 C Mechanism CHCH 3 H 2 C CHCH 3 •
. . RO: H 2 C Mechanism CHCH 3 H 2 C CHCH 3 • H 2 C CHCH 3
Likewise. . . • H 2 C=CHCl • H 2 C=CHC 6 H 5 • F 2 C=CF 2 polyvinyl chloride polystyrene Teflon
Important constitutions for synthetic polymers 19
Supramolecular structure of polymers 20
Structural properties of linear polymers: conformational flexibility and strength 21
Molecular Structure of Polymers Linear High Density Polyethylene (HDPE), PVC, Nylon, Cotton Branched Low Density Polyethylene (LDPE) Cross-linked Rubber Network Kevlar, Epoxy
Chain Length: 1000 - 2000 Low-Density Polyethylene (LDPE)
Chain Length: 4, 000 – 5, 000 PVC – (polyvinyl chloride) More Polar Stronger Bonding
Chain Length: 10, 000 – 100, 000 High-Density Polyethylene (HDPE)
Chain Length: 2 -6 million Ultra-high-molecular-weight polyethylene (UHMWPE) Joint Replacement Helmet Gears
Rubber Tree Sap: Sticky Viscous Gooey Goodyear Experiment Luck Profit ($0)
Vulcanization
Condensation polymerization: the polymer grows from monomers by splitting off a small molecule such as water or carbon dioxide. Example: formation of amide links and loss of water Monomers First unit of polymer + H 2 O 29
Chain Length: 4, 000 – 8, 000 Polyethylene Terephthalate (PETE) “Polyester” Ester
Kevlar Strong Network of Covalent Bonds And Polar Hydrogen Bonds
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Nylon
Hydrogen bonds between chains Supramolecular Structure of nylon Intermolecular hydrogen bonds give nylon enormous tensile strength 34
Biopolymers Nucleic acid polymers (DNA, RNA) Amino acids polymers (Proteins) Sugar polymers (Carbohydrates) Genetic information for the cell: DNA Structural strength and catalysis: Proteins Energy source: Carbohydrates 35
Proteins: amino acid monomers The basic structure of an amino acid monomer The difference between amino acids is the R group
Cotton Long Strands of Cellulose + Hydrogen Bonds Cellulose is the most common organic material on earth! It is also a primary constituent of wood and paper.
Polymers in Biology Starch DNA Sugar Proteins
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Proteins: condensation polymers Formed by condensation polymerization of amino acids Monomers: 20 essential amino acids General structure of an amino acid R is the only variable group Glycine (R = H) + Glycine First step toward poly(glycine) 40
Representation of the constitution of a protein 41
Three D representation of the structure of a protein 42
DNA
Thymine (T) The monomers: Adenine (A) Cytosine (C) Guanine (G) Phosphate. Sugar (backbone) of DNA 44
Phosphatesugar backbone holds the DNA macromolecule together 45
One strand unwinds to duplicate its complement via a polymerization of the monomers C, G, A and T 46
Carbohydrates
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Endless Possibilities New Functional Groups Different Polymer Backbones
Conclusions: Polymers make up all sorts of materials that are all around us! They can have a huge range or material properties based on their: Functional Groups Structure Backbone Keep thinking about how chemical interactions on the nano-scale correspond to material properties on the macro-scale
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