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Grade distribution for Exam 3
Exam 3 Histogram: Grade Frequency 5 10 15 20 25 30 35 4 7 13 16 19 22 28 Bin Frequency
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Synthetic and Biological Polymers
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
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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
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Example of addition polymers
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Free-Radical AdditionPolymerization of Ethylene
H2C CH2 200 °C 2000 atm O2 peroxides CH2 polyethylene 6
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Free-Radical Polymerization of Propene
H2C CHCH3 CH CH3 polypropylene 6
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.. RO Mechanism • H2C CHCH3 7
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.. RO: Mechanism H2C CHCH3 • 9
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.. RO: Mechanism H2C CHCH3 • CHCH3 H2C 10
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.. RO: Mechanism H2C CHCH3 H2C CHCH3 • 10
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.. RO: Mechanism H2C CHCH3 H2C CHCH3 CHCH3 H2C • 10
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.. RO: Mechanism H2C CHCH3 H2C CHCH3 H2C CHCH3 • 10
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.. RO: Mechanism H2C CHCH3 H2C CHCH3 H2C CHCH3 CHCH3 H2C • 10
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Likewise... H2C=CHCl polyvinyl chloride H2C=CHC6H5 polystyrene
F2C=CF Teflon 19
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Important constitutions for synthetic polymers
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Supramolecular structure of polymers
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Structural properties of linear polymers: conformational flexibility and strength
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Cross linking adds tensile strength
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Condensation polymerization
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 + H2O
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In the 1967 movie, "The Graduate”,
Polymers in the movies In the 1967 movie, "The Graduate”, a smug Los Angeles businessman takes aside the baby-faced Dustin Hoffman and declares, "I just want to say one word to you -- just one word -- 'plastics.' " In 2005 we can replace ‘plastics’ with another word: ‘synthetic polymers’
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Hydrogen bonds between chains
Supramolecular Structure of nylon Intermolecular hydrogen bonds give nylon enormous tensile strength
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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
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Proteins: amino acid monomers
The basic structure of an amino acid monomer The difference between amino acids is the R group 4
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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)
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Representation of the constitution of a protein
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Three D representation of the structure of a protein
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DNA 4
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Thymine (T) The monomers: Adenine (A) Cytosine (C) Guanine (G)
Phosphate- Sugar (backbone) of DNA
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Phosphate-sugar backbone holds the DNA macromolecule together
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One strand unwinds to duplicate its complement via a polymerization of the monomers
C, G, A and T
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Carbohydrates 4
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