Transcript polymers - ClassNet

POLYMERS
DEFINITIONS
Monomer
• A small molecule with a relatively low molar
mass. When many monomers are bonded
together, a polymer is formed.
Polymer
• Larger than a monomer with a higher molar
mass. A polymer is formed by many
monomers bonded together in a chain or
network
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C==C + C==C  —C—C—C—C—
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MONOMERS
POLYMERS
POLYMERIZATION
1. Addition Polymerization
2. Condensation Polymerization
Addition Polymerization
Stage 1:
• Initiation
– The initiating molecule forms a bond to a
carbon atom in a double bond
– The unpaired electron that forms the bond
shifts to the other end of the original
double bond.
Addition Polymerization
Stage 2:
• Propagation
– The unpaired electron is now available to
form a covalent bond with another atom
– The term used when the chain adds more
atoms or groups is propagates
Addition Polymerization
Stage 3:
• Termination
– Occurs when two unpaired electron ends
combine and form a covalent bond
– Two growing chains are linked and can no
longer grow
Condensation Polymerization
Condensation polymers are formed when
monomer units bond through a condensation
reaction such as:
– Carboxylic acids reacting with alcohols to form
esters
– Monomer units reacting with amines to form
amides
• Esters form when a carboxylic acid reacts
with alcohol. When this process is
repeated to form multiple esters, that form
a long chain, and a polyester is produced.
This occurs when dicarboxylic acid is
added to a diol to form the polyester and
water molecule
• Di-methanoic acid + 1,2-ethenediol  polyester + water
A—A + B—B + A—A + B—B 
A—[AB]—[BA]—[AB]—B + water
=A—A (acid) =B—B (alcohol) =AB (ester link)
POLYAMIDES
Formed when condensation reactions result in
the formation of amide bonding between
monomers. They are formed by condensation
reactions between a carboxylic acid and an
amide, with the removal of the water molecule
O
O
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n[—C—N—C—N—]n
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H
H
CROSS LINKAGE
Cross links are bridges which are formed
between two separate polymer chains,
connecting the polymers together. Cross
links help to strengthen polymers. The
more cross links that are formed, the
stronger the attraction holding the chain
together, due to covalent bonding.
CH=CH2 + CH=CH2  CH—CH2—CH—CH2
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BIOLOGICAL
POLYMERS
Protiens: Amino Acids
Amino acids contain a carboxylic acids and an
amine which are both attached to a central atom.
The amino acids both combine as monomers to
form the larger polymer, the protein. The amino
acids can arrange and form various structures of
proteins, with varying properties. The varying
properties and arrangement leads to the many
different proteins, found in living organisms. All
amino acids can form two different isomers,
therefore known as ‘chiral molecules’. A chiral
molecule is able to exist in two forms, which
mirror each other.
The amino acids are linked together by
addition reactions. An amine group
from one amino and the acid group
from the other amino bond to form a
chain of amino acids, this is know as a
peptide bond. When a peptide bond
forms, a polypeptide is created. A
peptide is a polymer made up of amino
acids joined by peptide bonds. When
an amino acid joins at a peptide bond, a
dipeptide is formed.
H O
H
O
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H2N—C—C—[OH + H]N—C—C—OH 
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R’
R”
Amine 1
Amine 2
H O
H O
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 H2N—C—C—N—C—C—OH + H2O
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R’
R”
Dipeptide
PROTEIN STRUCTURE
The protein molecule’s structure
depends on the electron attraction and
repulsion of the amino acid. There are
four different protein structures:
– Primary
– Secondary
– Tertiary
– Quaternary
PRIMARY
The original structure known as a
polypeptide, which is the long strings
of amino acids arranged in a certain
order.
SECONDARY
• The amino acids, which are either polar
or non-polar, that interact within the
polypeptide
• This forms the ‘coils’ or ‘pleated
sheets’ through forces such as Van der
Waals, hydrogen bonding, etc.
TERTIARY
• Pleated sheet sections and hetical
sections are found together within the
same protein molecule
• They attract each other forming shapes
that are spherical or globular
QUARTERNARY
• Van der Waal forces join two or more
protein subunits together
• Example: in hemoglobin four protein
subunits are joined in a tetrahedral
shape
POLYMERS OF SUGARS
MONOSACCHARIDE
• Carbohydrate consisting of a single sugar
unit
• Arranged in a carbon backbone, usually 6
carbons long
• Some sugars, such as glucose, have a
carbonyl group on the first carbon to form an
aldehyde
• Other sugars, such as fructose, have a
carbonyl group on the second carbon
keytone
• Glucose is a aldose. Fructose is a keytose
GLUCOSE:
O
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CH2—CH—CH—CH—CH—C—H
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OH OH OH OH OH
FRUCTOSE:
O
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CH2—CH—CH—CH—CH—C—CH2
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OH OH OH OH OH
OH
Polymethylmethacrylate
(PMMA)
[also known as Plexiglas]
PMMA
• PMMA is a acrylate polymer
• Other acrylate include; Poly(butylenes
terephthalate) and Poly(methyl acrylate)
• PMMA is also found in acrylic paint.
• PMMA was first discovered in the 1870's, but
was first commercialized by Rohm and Haas
in 1935 as Plexiglas. DuPont brought out
PMMA as Lucite in 1937
Structural Diagram of PMMA:
SYNTHESIS
• Free radical polymerization of the monomer methyl
methacrylate.
• The carbon-carbon double bond is broken and the
free radical electrons create bonds more of the
methyl methacrylate monomer in an addition reaction
creating a chain of methyl methacrylate, known as
poly(methyl methacrylate).
PROPERTIES
•
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State: Solid
Melting point: 490° F (254.5° C)
Tensile Strength: 7000 psi
Compression Strength: 11500 psi
Flexural Strength: 10500 psi
Chemical Restance:
– Acids: Resistant
– Alkalis: Very Resistant
– Solvents: Poorly Resistant
• Forms: Sheets, blocks, moldings, etc.
(basically can be molded into any shape)
USAGE
• PMMA is used as a glass substitute. Known
commonly as Plexiglas it is used in hockey arenas to
shield fans from speeding pucks. Other sports uses
include basketball backboards and helmet visors.
PMMA is found in many common items such as
acrylic paint, and various figurines, or even a chess
set. Its strong and versatile, as well as fairly
inexpensive, so many companies use it for toy
components. It was once used as a corrective lens
but due to it’s poor gas permeability, PMMA caused
the eyes to become irritated and swollen. Today
polymers that allow oxygen to pass through are
used.