experiment 10: polymers. history the first synthetic polymers was bakelite, a phenol-formaldehyde...
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Experiment 10:Polymers
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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
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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
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Polymers
• There are natural polymers and synthetic polymers.
• Natural polymers– DNA, proteins, starches
• Synthetic polymers –– Polyurethanes, Styrofoam
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Methods of ProductionTwo 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 Plexiglass2. 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
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Homopolymers vs. Copolymers
• Homopolymer – polymer comprised of a single type of monomer unit
• Copolymer (also called a heteropolymer) – contains two ore more distinct momomers
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Chain-reaction polymersPolystyrene is a simple polymer made from repeating units of styrene.
CH=CH2R . CH-CH2-R
.
CH=CH2
.CH-CH2-CHCH2-R
(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.
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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.
O
O
n
Polyvinyl Acetate
Saponif icationO
n
Polyvinyl Alcohol
H
+O
OH
+ H2O
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Step-growth polymerization – Release of water
O
CH
CH2
CH2
O
HC
H2C
H2C
HC
B
O
O
CH2
Na
H2C
n
+ 4 H2O
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Recycling Codes
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TODAY
• The properties of 3 polymers will be investigated.
1. SOLUBILITY OF POLYSTYRENE
H2C CH
Styrene monomerPhenyl ethene
HC
H2C
n
Polystyrene or styrofoam
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2. HOW MUCH WATER CAN IT HOLD?
• http://www.cmu.edu/gelfand/k12-teachers/polymers/polymer-and-absorption/super-absorb-powder.html
3. CROSS-LINKED POLYMER“SLIME”
O
OH
Acrylic Acid
Na+C
CHH2C
O
O-
n+ Na + OH
sodium polyacrylate
Initiator
O
CH
CH2
CH2
O
HC
H2C
H2C
HC
B
O
O
CH2
Na
H2C
n
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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.