Grade distribution for Exam 3
Frequency
Exam 3 Histogram:
Grade Frequency
35
30
25
20
15
10
5
0
Frequency
Bin
1
Synthetic and Biological Polymers
Polymers: Macromolecules formed by the covalent
attachment of a set of small molecules termed monomers.
Polymers are classified as:
(1)
Man-made or synthetic polymers that are
synthesized in the laboratory;
(2)
Biological polymer that are found in nature.
Synthetic polymers: nylon, poly-ethylene, poly-styrene
Biological polymers: DNA, proteins, carbohydrates
2
Methods for making polymers
Addition polymerization and condensation polymerization
Addition polymerization: monomers react to form a
polymer without net loss of atoms.
Most common form: free radical chain reaction of
ethylenes
n monomers
one polymer molecule
3
Example of addition polymers
4
Free-Radical AdditionPolymerization of
Ethylene
H2C
CH2
200 °C
2000 atm
CH2
CH2
CH2
CH2
O2
peroxides
CH2
polyethylene
CH2
CH2
Free-Radical Polymerization of Propene
H2C
CH
CH
CH3 CH3
CHCH3
CH
CH
CH
CH
CH
CH3
CH3
CH3
CH3
CH3
polypropylene
..
•
RO
..
H2C
Mechanism
CHCH3
Mechanism
..
RO:
H2C
CHCH3
•
..
RO:
H2C
Mechanism
CHCH3
•
H2C
CHCH3
..
RO:
H2C
Mechanism
CHCH3
H2C
CHCH3
•
..
RO:
H2C
Mechanism
CHCH3
H2C
CHCH3
•
H2C
CHCH3
..
RO:
H2C
Mechanism
CHCH3
H2C
CHCH3
H2C
CHCH3
•
..
RO:
H2C
Mechanism
CHCH3
H2C
CHCH3
H2C
CHCH3
•
H2C
CHCH3
Likewise...
•H2C=CHCl
•H2C=CHC6H5
•F2C=CF2
polyvinyl chloride
polystyrene
Teflon
Important
constitutions
for synthetic
polymers
15
Supramolecular
structure of
polymers
16
Structural
properties of
linear
polymers:
conformationa
l flexibility
and strength
17
Cross linking adds
tensile strength
18
Condensation polymerization
Condensation polymerization: the polymer grows from
monomers by splitting off a small molecule such as
water or carbon dioxide.
Example: formation of amide links and loss of water
Monomers
First unit of polymer + H2O
19
Polymers in the movies
In the 1967 movie, "The Graduate”,
a smug Los Angeles businessman takes aside the
baby-faced
Dustin Hoffman and declares,
"I just want to say one word to you -- just
one word -- 'plastics.' "
In 2005 we can replace ‘plastics’ with
another word: ‘synthetic polymers’
20
Rembember from GChem?
Nylon is a condensation polymer
made of the monomers adipic acid
and hexamethylene diamine.
O
OH
O
OH
Q uickTim e™ and a
Phot o - JPEG decom pr essor
ar e needed t o see t his pict ur e.
They're nylons, Benjamin.
adipic acid
+
NH2
H2N
hexamethylene diamine
nylon
21
Hydrogen bonds between chains
Supramolecular
Structure of
nylon
Intermolecular
hydrogen bonds
give nylon
enormous tensile
strength
22
Biopolymers
Nucleic acid polymers (DNA, RNA)
Amino acids polymers (Proteins)
Sugar polymers (Carbohydrates)
Genetic information for the cell: DNA
Structural strength and catalysis: Proteins
Energy source: Carbohydrates
23
Proteins: amino acid monomers
The basic structure of an amino acid monomer
HO
NH2
H
O
R
The difference between amino acids is the R group
25
Proteins: condensation polymers
Formed by condensation polymerization of amino acids
Monomers: 20 essential amino acids
General structure of an amino acid
NH2
H
R
CO2H
R is the only variable group
Glycine (R = H) + Glycine
First step toward poly(glycine)
26
Representation of the
constitution of a protein
27
Three D representation of the structure of a protein
28
DNA
Thymine (T)
The monomers:
Adenine (A)
Cytosine (C)
Guanine (G)
PhosphateSugar (backbone) of
DNA
30
Phosphatesugar
backbone
holds the DNA
macromolecule
together
31
One strand
unwinds to
duplicate its
complement via a
polymerization of
the monomers
C, G, A and T
32
Carbohydrates
34