Chapter 4 Step-Reaction polymerization

Chemical and Bioengineering

Konkuk University

Oct. 10, 2008

0820

4-1. Classification of polymerization reaction

Mechanism- Stepwise polymerization (random union of monomers)

- Chain polymerization (successive linking of monomers to the end of

growing chain)

Morphology - Condensation polymerization - Addition polymerization

Reaction- Linear polymerization

- Cyclo polymerization

- Ring opening polymerization

- Transfer polymerization

- Elimination polymerization

Catalyst chemistry- Radical polymerization- Ion (Cation, Anion) polymerization

Carothers classification – based on whether the repeating unit of the polymer has the same atoms or different.

Addition polymers

-Has same atoms as the monomer

-Reaction is addition polymerization

Condensation polymers

- Fewer atoms because of formation of byproducts during polymerization (condensation polymerization)•Same polymer can be synthesized by addition or condensa

tion polymerization (Eg: polyether synthesis from ethylene oxide and ethylene glycol).

4-1-1. condensation polymerization and addition polymerization

축합중합 (condensation polymerization):

- the monomer molecules bond is often a condensation rea

ction that produces a small molecule byproduct- polypeptide 

(1) General Reaction

부가중합 (addition polymerization): - from the monomer

- Vinyl 중합체

- polyethylene, polystyrene, natural rubber

Isoprene

The point at issue: condensation polymerization VS addition polymerization

Nylon6 Caprolactam w-Aminocaproic acid

Polyethylene

Ethylene Diazomethane

Dihaloalkane

4-1-2. Step-reaction polymerization and chain-reaction polymerization

단계반응중합 (step-reaction polymerization):

- a polymerization process that involves a chemical

reaction between multifunctional monomer molecules (In a

step-growth reaction, the growing chains may react with each

other to form even longer chains.)

Step-reaction polymerization

The molecular weight of growing chain is low.

P = 반응 전환율

N0 = 초기 분자 수

N = 반응 후 분자 수

= N0 /N 98% 전환율 DP = 50

분자량 증가가 느림

연쇄반응중합 (chain-reaction polymerization):

- -high molecular weight are reached rapidly at low monomer

conversions

Step-reaction polymerization

4-1-2. Step-reaction polymerization & Chain-reaction polymerization

4-1-3. The type of step-reaction polymerization

(1) Self-polycondensation

(2) Polycondensation

4-2. The kinetics of step-reaction polymerization

4-2-1. The reaction of functional group

different from chain-polymerization: the kinetics

- the important of the functional group’s reaction, The molecular weight is increased

slowly

n-mer + m-mer (n+m)-mer

H O CC

O

Polyester is made from the two monomers, terephthalic acid (note: “ph” is silent) and ethylene glycol (car antifreeze). This makes a popular plastic called PETE, which is short for Polyethylene Terephthalate.. The synthesis is also a dehydration reaction because water is given off.

Hence the name POLYESTERESTER groups formed

PETE

CCCC

HH

HH HH

HH-

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-

-

Ethylene has two carbons; plus, instead of the two carbons sharing just one electron each, they share two electrons each. High temperature or UV light can cause two of these shared (paired) electrons to become unshared (unpaired).

These unpaired electrons are eager to pair up with another electron. If this ethylene molecule bumps another ethylene molecule, the unpaired electrons will cause the one it bumped into to lend one of its inner electrons.

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-

-

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-

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-

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HH

HH HH

CC

HH

CC

Here’s another way to see the chain reaction. These are the carbon atoms with their double-bond (2 shared electrons each). The hydrogen atoms are not shown. A collision breaks the first bond.

Once the first double bond is broken, a chain reaction will occur. In about a second an entire chamber of compressed ethylene gas turns into the polymer, polyethylene.

There are two types of polyethylene polymers (plastics). One is when the polyethylene exists as long straight chains. The picture here shows the chains of one carbon with two hydrogen atoms repeating. The chain can be as long as 20,000 carbons to 35,000 carbons. This is called high density polyethylene (HDPE).

high density polyethylene (HDPE); there must be low density polyethylene (LDPE). It is made by causing the long chains of ethylene to branch. That way they cannot lie next each other, which reduces the density and strength of the polyethylene. This makes the plastic lighter and more flexible.

Another polymer, which is almost the same as polyethylene, is PolyVinyl Chloride or PVC. The difference is that every other hydrogen is replaced with a chlorine atom (green sphere).

A polyester fiber used for surgical sutures is poly[oxy(1-oxoethylene)]. Write the structure and suggest an alternate name.

Write the alternate name for poly(iminohexane-1,6-diyliminoadipolyl)