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Polymerization. Section 7. Polymerization. The process of chemically linking monomers together to form macromolecules In our discussion we will not include natural polymers Essentially there are two types of polymerization Addition Polymerization Condensation Polymerization.

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Polymerization

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Polymerization l.jpg

Polymerization

Section 7


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Polymerization

  • The process of chemically linking monomers together to form macromolecules

  • In our discussion we will not include natural polymers

  • Essentially there are two types of polymerization

    • Addition Polymerization

    • Condensation Polymerization


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Addition Polymerization

The entire monomer molecule becomes part of the polymer

  • A polymerization where unsaturated monomers combine without rearrangement of their structure

  • This is sometimes referred to as vinyl or chain polymerization

  • This process is essentially a three step process

  • The monomer is added to the polymer outright


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Addition- Step 1

  • Step 1 is called initialization (I)

    • An initiator through the application of thermal energy breaks down to form two radicals


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Addition- Step 2

  • Step 2 is called growth

    • This is where a radical is combined with a monomer forming a two unit (mer) molecule

    • This radical-monomer is then combined with a second monomer adding it in a linear arrangement.

    • This continues until it reached the final step


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Addition- Step 3

  • Step 3 is called termination

    • Chains that are propagating along are terminated by either having the two ends of growing chains meet and quench the reaction or by having a monomer donate a proton to the growing chain thereby quenching the reaction


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Addition Examples

  • Example 1: Polyethylene (PE)

C8- gasolineC12- oilC18- wax

C100- low MW PEC1000- MDPEC3000- HDPE


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Addition Examples

  • Example 2: Polyvinylchloride (PVC)

    • Illustrates head-to-tail polymerization

    • Clear, toxic monomer

    • Degrades need melt point ?? Needs plasticizers

    • Plastisol is common combination of LMW PVC & WAX, DOP

    • People hate to mold it


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(b)

(a)

  • Note: Head-to-tail addition is favored because the one configural form (a) of the adding chain is more stable than the other configural form (b) of the monomer added to the chain, which is made and unmade

Examples: PE, PP, PS, PVC


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Addition Examples

  • Example 3: Polystyrene (PS)

    • clear

C2H3C6H5 Polystyrene


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Addition Examples

  • Example 4: Teflon® (PTFE)

    • Never melts because of F-F interaction


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Addition Examples

  • Example 5: PAN

  • Rayon- Cellulose Acetate; Orlon

  • Fiber and Films


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Polypropylene Coordination Polymerization

  • This is a special type of configurational polymerization that results in a molecule being added in only one manner

  • Specific form of a polymer made

  • Ex. PP


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Tacticity

  • The way pendant groups are arranged along the backbone chain of a polymer

  • Heavily pertains to vinyl polymers


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Isotactic

  • This is where the side groups are all on the same side of the carbon atoms

  • Like Cis


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Syndiotactic

  • This is where the carbon side groups are on alternating sides of the carbon chain

  • Desirable

  • Like Trans


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Atactic

  • This is where there is no regular or repeated method to the arrangements on the side groups of the carbon chain


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Condensation Polymerization

Part of the monomer molecule (a small molecule) is kicked

out when the monomer becomes part of the polymer

  • Also known as step polymerization

  • This is the process where a chemical combination of two molecules takes place with the subsequent elimination of a small molecule (usually water or HCl gas)

  • The resulting larger molecule is the combination of the other components of the original two molecules

  • This is essentially a single step process

O

||

-H2O

Acid (RCOOH) + Alcohol (R1- OH) R-C-O-R1

-H2O

Acid (RCOOH) + R – NH2 RCOO – NH – R1


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Condensation Polymerization

  • Two functional groups are needed per molecule

  • These groups can be the same or different

  • They can be the same for each molecule and the number of functional groups on a molecule is referred to as its functionality


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Condensation Examples

  • Examples:

  • Acid plus alcohol equals yield as ester plus water

  • An acid plus an amine gives an amino acid plus water


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Condensation Examples

  • Nylon- It’s a di acid plus a diamine and it yields a polyamide

HOOC(CH2)4 COOH + H2N – (CH2)6 – NH2

H2O


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Condensation Examples

  • Example 1: Nylon 6,6

Note: The nomenclature for nylon is based on the number of carbon atoms in each of the two monomers that make up the nylon molecules


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Condensation Examples

  • Polyester- this is a diacid plus a dialcohol and yielding a polyester

Need

Or from diacids

Terephthalic Acid

H2O


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Condensation Examples

  • Polyester

    • Note: If both R1 and R2 are aliphatic the product is too soft

    • If both are aromatic the product is too hard

    • For PET one is ethyl or butyl and R2 is phenyl

    • This results in polyethylene terephthatic

Aromatic: possessing thermal stability, a tendency to undergo electrophilic substitution rather than addition reactions, and resistance to oxidation

Aliphatic: used to describe non-aromatic hydrocarbons with no ring structures present


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Condensation Examples

  • Polycarbonate- this is carbonic acid and a phenolic diol

H2O


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You might say that an addition polymer is like a good friend who accepts everything about you, the pleasant and the unpleasant alike.

But a condensation polymer is more like a snotty social club that says, "Sure you can join, but only if you ditch

those friends of yours".


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Addition

Only growth reaction adds units to the chain

Condensation

Any two species can react

Polymerization Comparison


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Polymerization Comparison

Condensation

2. Monomer Concentration

Addition2. Monomer concentration


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Addition

2. Highpolymer formed early

Condensation

2. Molecular weight rises steadily

Polymerization Comparison


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Addition

3. As time increases high conversions but no effect on molecular weight

Condensation

3. As time increases it gives higher and higher molecular weights

Polymerization Comparison


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Addition

4. At any time there is only monomer, highpolymer and a small amount of initiator

Condensation

4. At any time during the reaction there are small polymers, as well as intermediate size polymers, plus monomers present

Polymerization Comparison


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Polymerization Comparison

Condensation

4. Molecular Weight %

Addition

4. Molecular Weight %


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Where do polymers get their names?

1. Their name based on the organic material they are derived from

Ex. Cellulose acetate

2. They are named after the monomers that make them

Ex. Ethylene, propylene, and urea

3. They are named for their chemical name

Ex. Polypropylene and polyethylene


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Where do polymers get their names?

4. They get their name from a contraction of their chemical name

Ex. Vinyl, acrylic, oelfin

5. Names can be based on their initials

Ex. PS, ABS, PP, and PE

6. They get their names from trade names

Ex. Bakelite, Lexan, Teflon, and Nylon


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Area of application

Polymer Properties

Method of fabrication

Filler and addition type

Food grade or medical grade

High heat or High impact

Extrusion or injection

Glass filled or mica filled/addition

Classificationof Polymers (Grades)

Thereare 1000 grades of PE


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Density

Plastics are bought by weight and sold by volume

Density = Mass/Volume Density= D= ρ (rho)

OR

ρ= M/V therefore M= V* ρ

Specific Volume

ρ = 1/(SV)


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Where do polymer raw materials come from?

  • Crude Oil

  • Natural Gas


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