Transcript Polymerization Reactions - SCH4U1-CCVI

Polymers are large molecules made by
linking together many smaller molecules,
called monomers.
monomers
monomer
symbol
polymer
n
Natural polymers include proteins, carbohydrates
and lipids.
Synthetic polymers include plastics, nylon, acetate, and polyesters.
Polymerization reactions can either be classified as addition reactions
or as condensation reactions.
Addition Polymers
Addition polymerization is a reaction where monomer units join each
other in a process that involves the rearranging of electrons in double
or triple bonds in the monomer.
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-
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Ethene (ethylene) has two pairs of shared
electrons in the double bond.
High temperature or UV light can cause two
of these shared (paired) electrons to become
unshared (unpaired).
Polyethene (Polyethylene or Vinyl)
Here’s another way to see the chain reaction.
These are the carbon atoms with their doublebond (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.
When the chains
get up to 500,000
carbons long, they
are tough enough
for synthetic ice,
replacement joints,
and bullet-proof
vests.
This is called high
density polyethylene
(HDPE). See p. 139
in textbook
Low density polyethylene
(LDPE) 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.
Low density polyethylene is used to make things like plastic bags,
plastic wrap, and squeeze bottles.
Polypropene
It is more commonly called polypropylene.
Polypropylene is used to make things like
carpet, rope and thermal underwear.
Polyvinyl Chloride
PVC is one of the most widely used polymers, with dozens of
practical applications.
PolyVinyl Chloride (or PVC) is almost the same as
polyethylene, except every second hydrogen is replaced
with a chlorine atom (green sphere).
Polyvinyl Chloride (PVC)
upholstery
siding
wire insulation
pipes and fittings
raincoats
Polyvinyl Alcohol
• Uses include – white glue, post it notes,
“silly puddy”, “slime” etc…..
Polystyrene
When a benzene ring is attached to
an ethene molecule, it is commonly
called styrene.
Polystyrene
trays
cups
coolers
packing materials
Teflon
Teflon® is the product name for the polymer used
to make nonstick cookware.
It is composed of a series of tetrafluoroethene
monomers.
Recently, concern has been growing
regarding the possibility that Teflon®
releases toxic chemicals if it gets too hot.
Important
constitutions
for synthetic
polymers
19
Crosslinking
• By using another atom – C group or OH or S the polymer
can be strengthed and also control of the structure can
be forced
Condensation Polymers
Condensation polymerization involves the formation of a small
molecule (like H2O, NH3, HCl) from the functional groups of two
different monomer molecules.
The monomer molecules then bond at the site where the atoms have
been removed.
A synthetic compound that has a similar chemical structure to a
naturally occurring substance is called a structural analog.
Functional analogs are synthetic compounds that perform the same
function as a naturally occurring substance but do not necessarily
have similar structures (e.g. artificial sweeteners).
Polyesters
A polyester is a series of ester molecules joined in a long chain.
dicarboxylic acid + polyalcohol → polyester + water
The dicarboxylic acid has a carboxyl group at each end of the
molecule and the polyalcohol (a diol) has a hydroxy group at each end.
This makes the formation of a long chain of esters joined together
possible.
esterification
Notice two carboxyl
groups at the ends of
each carboxylic acid.
Notice two hydroxyl
groups at the ends of
each alcohol.
Nylon
Nylon is a synthetic structural analog to proteins, a natural product.
Nylon was synthesized as a substitute for silk, a natural polyamide.
The Hydrogen bonding cross linking of the Nylon gives it it’s strength.
Kevlar
The polymer chains form a
strong network of hydrogen
bonds that hold adjacent chains
together in a sheet-like structure.
Formation of a polyamide
O
HO
O
O
OH
NH2
OH
HO
NH2
Formation of a polyamide
O
HO
O
O
NH + H2O
HO O
H2N
NH2
OH
NH2
OH
Formation of a polyamide
O
O
O
HO
NH + H2O
HO O
H2N
NH
O
NH2
OH
NH2
OH
+ H2O
Formation of a polyamide
O
O
O
HO
NH + H2O
HO O
H2N
NH
O
NH
NH2
OH
+ H2O
+ H2 O
Formation of a polyamide
O
O
O
HO
NH
HO O
H2N
OH
NH
O
NH
NH2
A polyamide “backbone” forms with R groups
coming off. This protein is built with amino acids.