Fundamentals of Materials Science and Engineering: An Integrated Approach, 3e

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4.4 The Chemistry of Polymer Molecules • 101

Table 4.2 Some Common Hydrocarbon Groups

Characteristic Representative

Family Unit Compound

H C

H

H

OH

Alcohols R OH Methyl alcohol

H C

H

H

O C

H

H

Ethers R O R H Dimethyl ether

R C

O

OH

H C

H

H

C

O

OH

Acids Acetic acid

C O

H

R

C O

H

H

Aldehydes Formaldehyde

R

a

OH

Aromatic hydrocarbons Phenol

aThe simplified structure denotes a phenyl group,

C

C

C C

C C

H

H

H

H

H

small molecule from which a polymer is synthesized. Hence, monomer and repeat

unit mean different things, but sometimes the term monomer or monomer unit is

used instead of the more proper term repeat unit.

4.4 THE CHEMISTRY OF POLYMER MOLECULES

Consider again the hydrocarbon ethylene (C 2 H 4 ), which is a gas at ambient

temperature and pressure and has the following molecular structure:

C

HH

HH

C

If the ethylene gas is reacted under appropriate conditions, it will transform to

polyethylene (PE), which is a solid polymeric material. This process begins when an