Experiment 10:
Polymers
History
• The first synthetic polymers was Bakelite, a
phenol-formaldehyde polymer.
• Bakelite was commercially introduced in 1909. It
was developed as a synthetic substitute for
shellac.
• Used at first to make billiard balls but later used
for molded insulation, valve parts, knobs, etc.
• Rayon, the first synthetic fiber
• Precursors of Rayon
– 1884 – developed as artificial silk from collodion
• Marketed in 1891 but was short-lived
– Viscoid – 1892, a cellulose polymer
– Rayon – 1926, regenerated cellulose
Polymers
• Definition – A polymer is a molecule with a
very high molecular weight which is composed
of repeating simple structural units called
monomers. Often referred to as
macromolecules.
– Homopolymer – single recurring monomer
– Heteropolymer or Copolymer – at least 2 different
monomer subunits
Polymers
• There are natural polymers and synthetic
polymers.
• Natural polymers
– DNA, proteins, starches
• Synthetic polymers –
– Polyurethanes, Styrofoam
Methods of Production
Two major methods depending on the nature of the subunits…
1. Chain-reaction polymers (aka addition polymers)
• Monomers are attached to each other by a chain-reaction.
The reaction may have either a radical, an anion, or a cation as
an intermediate.
-Polypropene from propene, used in luggage and carpeting
-Polystyrene formed from styrene, used in packaging
-Polymethyl methacrylate formed from methyl methacrylate, also
known as Lucite or Plexiglass
2. Step-Growth Polymerization (aka condensation polymers)
• Monomers have functional groups at both ends. When these
ends react, the result is the polymer w/the loss of a small
molecule such as water or HCl.
- Usually natural polymers are formed in this way
- Monomer units can be different
Homopolymers vs. Copolymers
• Homopolymer – polymer comprised of a
single type of monomer unit
• Copolymer (also called a heteropolymer) –
contains two ore more distinct momomers
Chain-reaction polymers
Polystyrene is a simple polymer made from repeating units of styrene.
(R
. is an initiator)
Note : Most stable intermediate will
always be benzyl. The dimer shown
would continue the same steps
growing by one styrene each time.
Formation of “Slime”•
Tautomers of vinyl
alcohol
• PVA is not made from
vinyl alcohol because
aldehyde tautomer
favored.
• It is made from Polyvinyl
acetate with
saponification to the
alcohol.
+ H2O
Step-growth polymerization –
Release of water
+
4 H2O
Recycling
Codes
TODAY
• The properties of 3 polymers will be
investigated.
1. SOLUBILITY OF POLYSTYRENE
2. HOW MUCH WATER CAN IT HOLD?
• http://www.cmu.edu/gelfand/k12-teachers/polymers/polymer-andabsorption/super-absorb-powder.html
3. CROSS-LINKED POLYMER
“SLIME”
Waste
• Put your waste from each experiment into the
corresponding waste container….
– Experiment “A” goes into “A” waste container
– Experiment “B” goes into “B” waste container
– Experiment “C” goes into “C” waste container
• You may keep your SLIME!
… just don’t eat it.