1 synthetic and biological polymers polymers: macromolecules formed by the covalent attachment of a...

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1 Synthetic and Biological Polymers Polymers: Macromolecules formed by the covalent attachment of a set of small molecules termed monomers. lymers are large molecules made up of repeating uni lled Monomers.The synthetic process is Polymerizati C H 2 CH 2 CH 2 CH 2 O CH 2 CH 2 O M onom er Polymerization Polym er n M onom er Polymerization Polym er n

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Page 1: 1 Synthetic and Biological Polymers Polymers: Macromolecules formed by the covalent attachment of a set of small molecules termed monomers. Polymers are

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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 large molecules made up of repeating unitscalled Monomers.The synthetic process is Polymerization.

CH2 CH2 CH2 CH2

OCH2 CH2 O

Monomer

Polymerization

Polymern

Monomer

Polymerization

Polymern

Page 2: 1 Synthetic and Biological Polymers Polymers: Macromolecules formed by the covalent attachment of a set of small molecules termed monomers. Polymers are

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Polymers are classified as:(1)Man-made or synthetic polymers that are synthesized in the laboratory; (nylon, poly-ethylene, poly-styrene)

(2)Biological polymer that are found in nature. Biological polymers: DNA, proteins, carbohydrates

Homopolymer: A polymer prepared from a single monomer

Copolymer: If two or more different monomers are employed.

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Homopolymer & Copolymer

Page 4: 1 Synthetic and Biological Polymers Polymers: Macromolecules formed by the covalent attachment of a set of small molecules termed monomers. Polymers are

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Page 5: 1 Synthetic and Biological Polymers Polymers: Macromolecules formed by the covalent attachment of a set of small molecules termed monomers. Polymers are

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Polymerization

The chemical reaction in which high molecular mass molecules are formed from monomers.

There are two basic types of polymerization

1) Chain-reaction (or addition) polymerization

2) Step-reaction (or condensation) polymerization

Page 6: 1 Synthetic and Biological Polymers Polymers: Macromolecules formed by the covalent attachment of a set of small molecules termed monomers. Polymers are

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Methods for making polymers

Addition polymerization: monomers react to form a polymer without net loss of atoms.

This type of polymerization is a three step process involving two chemical components1)MonomerCan be regarded as one link in a polymer chain. It initially exists as simple units. In nearly all cases, the monomers have at least one carbon-carbon double bond. Ethylene is one example of a monomer used to make a common. polymer.

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2) Catalyst: In chain-reaction polymerization, the catalyst can be a free-radical peroxide added in relatively low concentrations

R-O-O-R 2 O-RA free-radical is a chemical component that contains a free electron that forms a covalent bond with an electron on another molecule.

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Polymerization Process (Mechanism)

Step 1: Initiation

The first step in the chain-reaction polymerization process, initiation, occurs when the free-radical catalyst reacts with a double bonded carbon monomer, beginning the polymer chain. The double carbon bond breaks apart, the monomer bonds to the free radical, and the free electron is transferred to the outside carbon atom in this reaction.

CH

H

H

H+

CH

H

H

HRO O-R

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2) Propagation Step

CH

H

H

H+C

H

H

H

HRO C

H

H

H

HC

H

H

H

HRO

Propagation polymer chain

monomer New polymer chain

The next step in the process, propagation, is a repetitive operation in which the physical chain of the polymer is formed. The double bond of successive monomers is opened up when the monomer is reacted to the reactive polymer chain. The free electron is successively passed down the line of the chain to the outside carbon atom

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Termination Termination occurs when another free radical (R-O.), left over from the original splitting of the organic peroxide, meets the end of the growing chain. This free-radical terminates the chain by linking with the last CH2

. component of the polymer chain. This reaction produces a complete polymer chain. Termination can also occur when two unfinished chains bond together.

CH

H

H

HC

H

H

H

HRO

n

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CH

H

H

HRO

OR

CH

H

H

HC

H

H

H

HRO

n

CHCH22 CHCH22 CHCH22 CHCH22 CHCH22 CHCH22 CHCH22

Page 12: 1 Synthetic and Biological Polymers Polymers: Macromolecules formed by the covalent attachment of a set of small molecules termed monomers. Polymers are

Monomer Polymer

EthyleneH3C

CH3

nRepeat unitPolyethylene

CH3

CH3n

CH3 CH3 CH3 CH3 CH3 CH3CH3Propylene

Polypropylene

PhCH3

n

Ph Ph Ph Ph Ph PhPhStyrene

Polystyrene

ClCH3

n

Cl Cl Cl Cl Cl ClClVinyl Chloride

Poly(vinyl chloride)

F2C CF2

Tetrafluoroethylene

F3C

F2C

CF2

F2C

CF2

F2C

CF2

F2C

CF2

F2C

CF2

F2C

CF2

CF3

nPoly(tetrafluoroethylene): Teflon

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Types of Addition Polymerizations

Ph

Anionic

C3H7 Li C4H9

Ph

Li+ Phn

C4H9

Ph Ph

Li+

n

Ph

Radical

PhCO2•Ph

n

Ph

Cationic

Cl3Al OH2H

PhHOAlCl3

Phn

H

Ph Phn

HOAlCl3

PhCO2

Ph

PhCO2

Ph Phn

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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

Page 15: 1 Synthetic and Biological Polymers Polymers: Macromolecules formed by the covalent attachment of a set of small molecules termed monomers. Polymers are

Nylon-6,6Cl Cl

O O

4H2N NH24

Adipoyl chloride 1,6-Diaminohexane

Cl NH

NH

H

O O

4 4

NaOH

HO NH

NH

H

O O

4 4n

6 carbondiacid

6 carbondiamine

Nylon-6,6Diamine, NaOH, in H2O

Adipoyl chloridein hexane

Nylon 6,6

Page 16: 1 Synthetic and Biological Polymers Polymers: Macromolecules formed by the covalent attachment of a set of small molecules termed monomers. Polymers are

Nylon-6,6

Diamine, NaOH, in H2O

Adipoyl chloridein hexane

Nylon 6,6

Since the reactants are in different phases, they can only react at the phase boundary. Once a layer of polymer forms, no more reaction occurs. Removing the polymer allows more reaction to occur.

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SupramolecularStructure of nylonIntermolecular hydrogen bonds give nylon enormous tensile strength

Hydrogen bonds between chains

Page 18: 1 Synthetic and Biological Polymers Polymers: Macromolecules formed by the covalent attachment of a set of small molecules termed monomers. Polymers are

Polyesters, Amides, and UrethanesMonomer Polymer

CO2HHO2CHO

OHO O

HO OH2C

H2C O

nTerephthalic acid

Ethyleneglycol

Poly(ethylene terephthalateH

Ester

HO OH

O O

4H2N NH24

Adipic Acid 1,6-Diaminohexane Nylon 6,6HO N

HNH

H

O O

4 4n

CO2HHO2C

Terephthalic acid

NH2H2N

1,4-Diamino benzene

Kevlar

O

HO

OHN

HN H

n

Amide

HOOH

Ethyleneglycol

H2COCN NCO

4,4-diisocyantophenylmethaneSpandex

H2C

HN

HN

O

HO

O

OH2C

H2C O H

n

Urethane linkage

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A businessman takes aside the baby-faced Dustin Hoffman and declares,

In the 1967 movie, "The Graduate”,

"I just want to say one word to you -- just one word -- 'plastics.' "

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• Traditionally, the industry has produced two main types of synthetic polymer – plastics and rubbers.

• Plastics are (generally) rigid materials at service temperatures

• Rubbers are flexible, low modulus materials which exhibit long-range elasticity.

Range of Polymers

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Thermoplastics can be softened or melted by heatand reformed (molded) into another shape.Most addition polymers are thermoplastics. The polymer chains are held together by weakinteractions (noncovalent bonds) such as :??

Polymer Classifications

These interactions are disrupted by heating, allowing the chains to become independent of each other. Heating and reforming can be repeated indefinitely (if degradation doesn't occur). This allows recycling.

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Most polymers of high molecular weight are quite rigid.PLASTICIZERSCan be softened and made flexible by adding plasticizers

The plasticizer separates the individual polymer chains from one another. It acts as a lubricant which reduces the attractions between the polymer chains.

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