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Polymers and Polymerization

Key Concepts

Polymer: large molecules made up of many monomers
Monomer: simpler substance of which polymer is made
Addition Polymerization: monomers' double-bonds open up to form continuous chain
Condensation Polymerization: elimination of smaller molecule when functional groups react

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Addition Polymerization

Addition polymers form:

when unsaturated carbon (organic) molecules react to form a long chain polymer molecule
and no small molecules or atoms are eliminated during the reaction

The general reaction can be represented as:

nR-C=C-R'

catalyst
------->

-(-

R
|
C

R'
|
C

-)_n-

where R and R' can represent hydrogen atoms, halogen atoms, alkyl or other carbon-containing side chains.

Monomer Name
Monomer Structure Polymer Name
Polymer Structure Polymer Uses

ethene (ethylene)
CH₂=CH₂ polyethene (polythene or polyethylene)
-[-CH₂-CH₂-]_n- LDPE for sandwich wrap, cling wrap
HDPE for water pipes, wire insulation

propene (propylene)
CH₂=CHCH₃ polypropene (polypropylene)
-[-CH₂-CHCH₃-]_n- electrical appliances, automotive applications, ropes, carpets, films

chloroethane (vinyl chloride)
CH₂=CHCl polyvinyl chloride (PVC)
-[-CH₂-CHCl-]_n- indoor electrical conduit, underground water pipes

tetrafluoroethene (tetrafluoroethylene)
CF₂=CF₂ polytetrafluorethene (polytetrafluoroethylene, teflon)
-[-CF₂-CF₂-]_n- Insulation for wires, motors, generators, etc.
Anti-stick applications in cookware, bearings.

styrene (vinyl benzene)
CH₂=CH polystyrene
H
|
-[C-
|
H H
|
C-
|

]_n-
heat and electrical insulation, pipes

acrylonitrile (vinyl cyanide)
CH₂=CH-CN polyacrylonitrile
-[-CH₂-CHCN-]_n- acrylic fabrics stronger than wool

vinyl acetate
CH₃COOCH=CH₂ polyvinylacetate (PVA)
-[-CH₃COOCH-CH₂-]_n- adhesives, paints

Condensation Polymerization

Condensation polymers form:

when bifunctional monomers react to form a long chain polymer molecule
small molecules, such as water, are eliminated during the reaction

Polyesters, polyamides, proteins and polysaccharides such as cellulose, are all examples of condensation polymers.

Polyesters

Polyesters form when the -OH functional group of one monomer reacts with the -COOH functional group of another monomer.
An ester link (-COO-) is formed between monomers during the reaction.
H₂O is eliminated in the reaction.

General reaction between a dicarboxylic acid and a diol:

HO
|
C
||
O - R - OH
|
C
||
O + HO- R'-OH -----> OH
|
C
||
O -R-

C
||
O -O-R'-OH + H₂O

Example:
terephthalic acid + ethylene glycol -----> polyethyleneterephthalate (terylene or dacron)

nHOOCCOOH + nHO-(CH₂)₂-OH -----> -(-OCCOO-(CH₂)₂-O-)_n- + nH₂O

Polyamides

Polyamides form when when the -COOH functional group of one monomer reacts with the -NH₂ functional group of another monomer.
An amide link or peptide bond (-CO-NH-) forms between monomers during the reaction.
H₂O is eliminated in the reaction.

Proteins are naturally occurring polyamides.

General reaction between a dicarboxylic acid and a diamine:

HOOC-R-COOH + H₂N-R'-NH₂ -----> HOOC-R-CONH-R'-NH₂ + H₂O

Example:
hexanedioc acid + 1,6-hexanediamine ---> nylon-6,6 + water
nHOOC-(CH₂)₄-COOH + nH₂N-(CH₂)₆-NH₂ ---> -(-OC-(CH₂)₄-CONH-(CH₂)₆-NH-)_n- + nH₂O