Historical Background
Ages ago - Natural Fibers Ex. Wool, silk, cotton
In 1736, Charles Marie de La
Condamine introduced the para
rubber tree (natural rubber).
Hevea brasiliensis
Natural (hevea) rubber known as
polyisoprene in its synthetic form.
“Crying tree”
(para rubber)
Latex Coating
Historical Background
1839-Charles Goodyear
Vulcanization: Transformation of sticky natural rubber to a useful
elastomer for tire use
S8
1843-Charles Goodyear
Ebonite High % vulcanization
(1st synthetic plastic made from natural rubber)
Fountain pen bodies
smoking pipe mouthpiece
bowling balls
Synthetic Polymers Started
1847
“Cellulose
nitrate”
cellulose
cellulose nitrate
1860s -Parkes (Electrical industry) and Hyatt (Billiard balls)
“Celluloid”
(1st artificial thermoplastic)
Cellulose nitrate+ Camphor (as plasticizer)
1907-Leo Baekeland “Bakelite”
(thermosetting phenol-formaldehyde resin)
Bakelite letter opener
Bakelite radio
On further heating with HCHO, novalac undergoes cross-linking to an infusible solid called bakelite. It is hard scratch and water resistant.
Bakelite telephone
1st truly synthetic plastic
Bakelite distributor rotor
Nobel Prize-Chemistry 1953 for “his discoveries in the field of macromolecular chemistry”
1920 “Macromolecular Hypothesis”
Demonstrations of both synthetic and natural polymers
Polymer is a giant molecule
long chains of short repeating
molecular units linked by covalent bonds
A chain of paper clips (above) is a good
model for a polymer such as polylactic acid (below).
Hermann Staudinger
Development of commercial polymers
1927 PVC
1931 PMMA & Neoprene
1938 Nylon
1941 LDPE
1943 Silicones
1947 Epoxy resins
1948 ABS
1957 HDPE
Definitions
Polymer science is relatively a new branch of science . It deals with chemistry
physics and mechanical properties of macromolecule .
Polymer –is a large molecule consisting of a number of repeating
units with molecular weight typically several thousand or higher
Polymers are made up of many Monomers
Many units
One units
Repeating unit – is the fundamental recurring unit of a polymer
Monomer - is the smaller molecule(s) that are used to prepare a
polymer
Oligomer –is a molecule consisting of reaction of several repeat
units of a monomer but not large enough to be consider a polymer
(dimer , trimer, tetramer, . . .)
Degree of polymerization (DP)- number of repeating units
Polymers vs Macromolecules
Polypropylene (PP)
DNA
1
2
3
Nylon 6,6
POLYETHYLENE
Zig-zag conformation
Substituent groups such as –CH3, -OCOCH3, CN, Cl or –Ph that are attached
to the main chain of the skeletal atoms are known as pendant groups. Their
structure and chemical nature can offer unique properties on polymer.
Classification of Polymers
A. Classification by Origin
• Natural Polymers
-Biological Origin - enzymes, nucleic acids, proteins
-Plant Origin – cellulose, starch, natural rubber
•Synthetic Polymers
- Fibers
- Elastomers
- Plastics
-Adhesives
3.Classification by Polymerization Mechanism
Classification of polymers to be suggested by Carothers
Addition polymers are produced by reactions in which monomers are added
one after another to a rapidly growing chain. Most important addition polymers
are polymerized from ethylene based polymers.
•Initiation
•Propagation
Unsaturated (C-C double bond)
(ethylene based monomers)
•Termination
Ring opening polymerization
Polyoxymethylene
Trioxane
2.Classification by Polymerization Mechanism
Condensation polymers are obtained by random reaction of two molecules.
A molecule participating in a condensation reaction may be a monomer, oligomer, or high molecular
weight intermediate each having complementary functional end units, such as carboxylic acid or
hydroxyl groups. Typically condensation polymerizations occur by the liberation of a small molecule in
the form of gas, water, or salt.
More recently, another classification scheme based on polymerization kinetics has been adopted
over the more traditional addition and condensation categories.
•
Step growth
•
Chain growth
3.Classification by Polymer Structure
Classification by Chain structure (molecular architecture)
(a) linear
(b) branch
The basic functionality required for forming even a linear chain is two
bonding sites.
Higher functionality yields branched or even crosslinked or networked
polymer chains.
Branched polymers have side chains, or branches, of significant
points (known as junction points), are characterized in terms of the
number and size of the branches
(c) network
Network polymers have three dimensional structures in which each
chain is connected to all others by a sequence of junction points and
other chains. Such polymers are said to be crosslinked and
characterized by their crosslink density, or degree of crosslinking,
which is related to the number of junction points per unit volume
Non linear polymers may be formed by polymerization, or can be prepared by linking together (ex.
crosslinking) pre-existing chains.
2.Classification by Polymer Structure
Classification by Chain structure (molecular architecture)
(d) ladder polymer
Ladder polymers constitute a group of polymer with a regular sequence of crosslinks.
diacetylene
2.Classification by Polymer Structure
Classification by Chain structure (molecular architecture)
(g) dendrimer
Dendrimers are repeatedly branched, roughly
spherical large molecules.
4.Classification by Polymer Structure
Classification by Monomer Composition
A. Homopolymer -contain only one type of repeat unit (A))
B. Copolymer -contain two different repeating units (AB)
If there are three chemically different repeating unit, it is then called terpolymer
Poly(styrene-co-acrylonitrile) (SAN)
Type of Copolymers
Random copolymer : -A-B-B-A-B-A-A-B-two or more different repeating unit are distributed randomly
Alternating copolymer : -A-B-A-B-A-B-A-B-are made of alternating sequences of the different monomers
Block copolymer :
-A-A-A-A-B-B-B-B-long sequences of a monomer are followed by long sequences of
another monomer
B-B-B-B-BGraft copolymer : -A-A-A-A-A-A-A-A-Consist of a chain made from one type of monomers with branches
of another type
5.Classification by Thermal Behavior
A thermoset is a polymer that, when heated, undergoes a chemical change to produce a
cross-linked, solid polymer.( Ex: urea-formaldehyde, phenol-formaldehyde, epoxies)
Thermoplastic polymers soften and flow under the action of heat and pressure. Upon
cooling, the polymer hardens and assumes the shape of the mold (container).
(Ex: polyethylene, polystyrene, and nylon)
Inorganic Polymers
Cl
CH3
O
N
Si
P
n
n
Cl
CH3
Poly(dichlorophosphazene)
polydimethylsiloxane
Polyelectrolytes
CH3
H2
C
H2
C
H
C
C
n
n
COOH
COOH
Poly(acrylic acid)
Poly(methacrylic acid)
Nomenclature
A. Types of Nomenclature
a. Source name : to be based on names of corresponding monomer
Polyethylene, Poly(vinyl chloride), Poly(ethylene oxide)
b. IUPAC name : to be based on CRU, systematic name
Poly(methylene), Poly(1-chloroethylene), Poly(oxyethylene)
c. Functional group name :
According to name of functional group in the polymer backbone
Polyamide, Polyester
Nomenclature
d. Trade name : The commercial names by manufacturer Teflon, Nylon
e. Abbreviation name : PVC, PET
f. Complex and Network polymer : Phenol-formaldehyde polymer
Vinyl polymers
A. Vinyl polymers
a. Source name : Polystyrene, Poly(acrylic acid),
Poly(α-methyl styrene), Poly(1-pentene)
b. IUPAC name : Poly(1-phenylethylene), Poly(1-carboxylatoethylene)
Poly(1-methyl-1-phenylethylene), Poly(1-propylethylene)
Polystyrene
Poly(acrylic acid)
CH2CH
CH2CH
CO2H
Poly(α-methylstyrene)
Poly(1-pentene)
CH3
CH2C
CH2CH
CH2CH2CH3
Vinyl polymers
B. Diene monomers
CH 2CH
HC
CH 2CH
CHCH 2
CH 2
1,2-addition
1,4-addition
Source name : 1,2-Poly(1,3-butadiene) 1,4-Poly(1,3-butadiene)
IUPAC name : Poly(1-vinylethylene)
Poly(1-butene-1,4-diyl)
Vinyl copolymer
Type
Connective
Example
Unspecified
-co-
Poly[styrene-co-(methyl methacrylate)]
Statistical
-stat-
Poly(styrene-stat-butadiene)
Random
-ran-
Poly [ethyelene-ran-(vinylacetate)]
Alternating
-alt-
Poly[styrene-alt-(maleic anyhride)]
Block
-block-
Polystyrene-block-polybutadiene
Graft
-graft-
Polybutadiene-graft-polystyrene
* A statistical polymer is one in which the sequential distribution of the monomeric units obeys the statistical laws. In the case of random copolymer, the
probability of finding a given monomeric unit at any site in the chain is independent of the neighboring units in that position.
Polystyrene-block-polybutadiene
Polystyrene-graft-polybutadiene
* Representative Nomenclature of Nonvinyl Polymers
Monomer
structure
Polymer
repeating unit
Source or
Common Name
IUPAC name
O
H2C
CH2
HOCH2CH2OH
CH2CH2O
CH2CH2O
Poly(ethylene glycol)
O
H2N(CH2)6NH2
HO2C(CH2)8CO2H
Poly(ethylene oxide)
Poly(oxyethylene)
Poly(oxyethylene)
O
NH(CH2)6NHC(CH2)8C
Poly(hexamethylene
Poly(iminohexanesebacamide) or Nylon6,10 1,6-diyliminosebacoyl)
Abbreviations
Abbreviation
Name
PVC
Poly(vinyl chloride)
HDPE
High-density polyethylene
LDPE
Low-density polyethylene
PET
Poly(ethylene terephthalate)
ABS
Arcylonitrile-butadiene-styrene resin
PBT
Poly(butylene terephthalate)
PE
Polyethylene
PMMA
Poly(methyl methacrylate)
PP
Polypropylene
PS
Polystyrene
PTFE
Poly(tetrafluoroethylene)
PEO
Poly(ethylene oxide)
Thermal Responses of Simple Molecules
Water exists at three distinct
physical states-solid, liquid and
gas (vapor)
Transitions between these
states occur sharply at constant
, well defined temperatures.
Thermal Responses of Polymers-1
 Polymers do not exist in the
gaseous state. At high T they
decompose.
The transition between solid and
liquid forms of a polymer is rather
diffuse and occurs over a
temperature range, whose
magnitude (of the order of 2-10 °C)
depends polydispersity of the
polymer
Thermal Responses of Polymers-2
The molecular motion in a polymer sample is promoted by its thermal agitation
It is opposed by the cohesive forces between structural segments (groups of atoms)
along the chain and between neighboring chains.
The cohesive forces and thermal transitions in polymers depend on the structure of the
polymers.
The glass transition temperature, Tg
The crystalline melting point, Tm
Temperatures at which
physical properties of
polymers undergo drastic
changes
Tg—transition from the hard and brittle glass into softer rubbery state (amorphous polymer- in the
amorphous regions of semicrystalline polymer)
Tm– corresponds to the temperature at which the last crystallite starts melting
depends on the crystallinity and size distribution of crystallites
Knowledge of thermal transitions is important in ;
The selection of proper processing and fabrication conditions
Characterization of physical and mechanical properties of a material
Determination of appropriate end uses
Amorf, yarı kristal ve kristal maddelerde ısıl geçişler sırasında gözlenen
davranış değişiklikleri
sıvı
sıvı
T
sıvı
Te
zamksı
kauçuğumsu
camsı
Amorf
esnek
termoplastik
katı
Tg
camsı
Yarı kristal
kristal
Tam kristal ve yarı kristal maddelerde davranış değişiklikleri belirgin, amorf maddelerde
camsı geçiş dışındakiler derecelidir.
Polimer Kimyası Prof. Dr. Mehmet Saçak (5. Baskı, Gazi Kitapevi)
Glass Transition Temperature
Polimer Kimyası Prof. Dr. Mehmet Saçak (5. Baskı, Gazi Kitapevi)
Thermal Transitions
1st order transition
Abrupt change in a fundamental
property such as enthalpy (H) and
volume (V)
Melting is a first order thermodynamic
transition
2nd order transition
First derivative of properties such as
enthalpy (H) and volume (V) changes
Heat Capacity
H
Cp  ( )p
T
Thermal Expansion Coefficien t
1 V
  ( )p
V T
Both Cp and  change abruptly at Tg.
Free Volume Theory
This theory considers the free volume (Vf) of a substance as the difference between its
specific volume (total volume) (V) and the space actually occupied by the molecules (Vo)
V  Vo  Vf
Specific Volume
V
f  f
V
Vo
Vf
Vf*
Tg
Temperature
(T)
f 
V f*
V
(constant)
Free Volume Fraction
V f  V f*  (T  Tg )(
V
)
T
f  f g  (T  Tg ) f
 f  1   2
Thermal expansion coefficient (below Tg
Thermal expansion coefficient (above Tg)
For whole range of glassy polymers, fg is remarkably constant and this concept of free
volume found important use in the analysis of the rte and temperature dependence of
viscoelastic behavior of polymers between Tg and Tg+100K
Factors Affecting Tg
Structural Features;
Chain Flexibility (stiffness, polarity,
steric hindrance)
Interchain Attractive Forces
Geometric Factors
Copolymerization
Molecular Weight
Branching and Crosslinking
Crystallinity
External Variables;
Plasticization
Pressure
Rate of Testing
Chain Flexibility
Chain flexibility is determined by the ease with which
rotation occurs about primary valence bonds. Polymers
with low hindrance to internal rotation have low Tg values
Long-chain aliphatic groups (ether-ester linkages) enhance flexibility
Cyclic structures stiffen the backbone
Chain Flexibility
Bulky side groups that are stiff and close to the backbone cause steric hindrance , decrease
chain mobility and hence raise Tg
Chain Flexibility
The influence of the side group in enhancing chain stiffness depends on
the flexibility of the group and not its size.
In fact, side groups that are fairly flexible have little effect within each
series; instead polymer chains are forced further apart.
This increases the free volume, and consequently Tg drops.
Geometric Factors
Polymers that have symmetrical structure
have lower Tg than those with asymmetric
structures.
The additional groups near the backbone
can be accommodated in a conformation with
a “loose” structure. The increased free
volume results in a lower Tg.
Geometric Factors
Double bonds in the cis form reduce the energy barrier
for rotation of adjacent bonds, “soften” the chain, and
hence reduce Tg
Interchain Attractive Forces
The effect of polarity
The steric effects of the pendant group in series (CH3, Cl, CN)
are similar but the polarity increases so Tg increases.
Interchain Attractive Forces
Hydrogen Bonding
Ionic Bonding
Any structural feature that tends to
increase the distance between polymer
chains decreases the cohesive energy
density and hence reduces Tg.
In the polyacrylate series shown above,
the increased distance between chains
due to the size of the alkyl group, R,
results in reduced Tg.
Copolymerization
To be able to control the Tg and Tm independent of each other is very difficult, but it is
solved to some extent by copolymerization of polyblending.
A copolymer system may be characterized by:
geometry of the resulting polymer (random, alternating, graft or block)
The compatibility (miscibility) of two monomer
Isomorphous Systems (Homogeneous Copolymers or Compatible Polyblends
In isomorphous systems, the component monomers occupy similar volumes and are capable of replacing
each other in the crystal system.
Copolymerization merely shifts the Tg to the position intermediate between those of the two homopolymers; it
does not alter the temperature range or the modulus within the transition region
Tg  V1Tg1  V2Tg 2 (1)
where;
Tg1 and Tg2 are Tg of individial homopolymers
V1 and V2 are volume fractions of components1 and 2
Variation in Tg
with copolymer
composition
Copolymerization
Nonisomorphous Systems In nonisomorphous systems, the specific volumes of the monomers
are different. In this case, the geometry of the resulting polymer becomes important.
Random and Alternating: The increased disorder resulting from the random or alternating distribution of
monomers enhances the free volume and consequently reduces Tg below that predicted by Equation 1.
1
W W
 1  2 (2)
T g Tg1 Tg 2
where;
Tg1 and Tg2 are Tg of individial homopolymers
W1 and W2 are weight fractions of components1 and 2
Examples of this type are methyl methacrylate–acrylonitrile,
styrene–methyl methacrylate, and acrylonitrile–acrylamide
copolymers. (Line 2-next graph)
It is also possible that monomers involved in the copolymerization
process (as in the copolymers methylacylate–methylmethacrylate
and vinylidene chloride–methylacrylate) introduce significant
interaction between chains. In this case the Tg will be enhanced
relative to the predicted value (line 3 –next graph)
Variation in Tg with
copolymer composition
Copolymerization
Block or Graft Copolymers (incompatible Copolymers): For block or graft copolymers in which the
component monomers are incompatible, phase separation will occur. Depending on a number of factors
— for example, the method of preparation — one phase will be dispersed in a continuous matrix of the
other. In this case, two separate glass transition values will be observed, each corresponding to the Tg of
the homopolymer.
Polyblends of polystyrene (100 ) and 30/70 butadiene- styrene copolymer
Molecular Weight
At a given temperature, therefore, chain ends provide a higher free volume for molecular motion.
As the number of chain ends increases (which means a decrease in Mn), the available free
volume increases, and consequently there is a depression of Tg.
The effect is more pronounced at low molecular weight, but as Mn increases, Tg approaches an
asymptotic value.
K
Tg  T 
Mn
where Tg  Tg of an infinite molecular weight

g
K  a constant
Crosslinking and Branching
Crosslinking involves the formation of intermolecular connections through chemical bonds, and this results
in chain mobility and Tg increases.
For lightly crosslinked systems like vulcanized rubber, Tg shows a moderate increase over the un
crosslinked polymer.
For the highly crosslinked systems like phenolics and epoxy resins, the Tg is virtually infinite.
Like long and flexible side chains, branching increases the separation between chains , enhances free
volume and decreases Tg
Crystallinity
In semicrystalline polymers, the crystallites may be regarded as the physical cross-links that to
reinforce or stiffen the chain. So Tg will increase with increasing crystallinity.
1 / 2 for symmetrical polymers 


Tm 2/3 for unsymmetrical polymers 
Tg
where Tg and Tm are in degrees Kelvin
Plasticization
Plasticity is the ability of material to undergo plastic or permanent deformation.
Plasticity is the process of inducing plastic flow in a material. In polymers, this can
be achieve by addition of low molecular weight organic compounds (plasticizers).
Plasticizers are nonpolymeric, organic liquids of high boiling points. They are
miscible with the polymer, and should remain in the polymer. (Very low Tg
between -50 °C and -160 °C)
Addition of a small amount of plasticizer drastically reduces the Tg of polymer.
Effect of plasticizer in reducing Tg
Plasticizers function through a solvating action by increasing
intermolecular distance, thereby decreasing intermolecular
bonding forces.
The addition of plasticizers results in a rapid increase in chain
ends and hence an increase in free volume.
A plasticized system may also be considered as a polyblend,
with the plasticizer acting as the second component
Crystalline Melting Point
Melting represents a true first order thermodynamic transition characterized by the discontinuities in the
primary thermodynamic values (heat capacity, specific volume (density), refractive index and tranparency.
G m  H m  Tm  m  0
Tm 
H m
Sm
where H m  enthalpy change during melting
Factors that determine crystallization
tendency;
Structural regularity
Chain Flexibility
Intermolecular Bonding
Sm  entropy change during melting
Melting in crystalline polymeric systems.
• The macromolecular nature of polymers and the existence of molecular
weight distribution (polydispersity) lead to a broadening of Tm.
• The process of crystallization in polymers involves chain folding. This creates
inherent defects in theresulting crystal. Consequently, the actual melting point
is lower than the ideal thermodynamic melting point.
• Because of the macromolecular nature of polymers and the conformational
changes associated with melting, the process of melting in polymer is more
rate sensitive than that in simple molecules.
• No polymer is 100% crystalline.
Factors Affecting
The Crystalline Melting Point Tm
Pesudoequi librium process
Tm 
H m
S m
where
H m  the difference in the cohesive energies between
chains in the crystalline and liquid states
Sm  difference in degree of order between molecules in the two states
Hm is independent of molecular weight. Polar groups on the chain would
enhance the magnitude of Hm
Sm depends not only molecular weight, but also on structural factors like chain
stiffness. Chains that are flexible in the molten state ( large number of
conformations than stiff chains) result in a large Sm
Intermolecular Bonding-1
The melting points approach that of
polyethylene as the spacing between
polar groups increases.
For the same number of chain atoms
in the repeat unit, polyureas,
polyamides, and polyurethanes have
higher melting points than polyethylene,
while polyesters have lower.
Trend of crystalline melting point in homologous
series of aliphatic polymers.
Ym =molar melt transition function
Intermolecular Bonding-2
The melting points of the nylons reflect the density of hydrogen forming amide linkages.
The densities of interunit linkages in polycaprolactone (ester units) and polycaprolactam
(amide units) are the same, but the amide units are more polar than the ester units.
Effect of Structure
Tg ( °K)
1 / 2 for symmetrical polymers 


Tm 2/3 for unsymmetrical polymers 
Tg
where Tg and Tm are in degrees Kelvin
Chain Flexibility
Polymers with rigid chains would be expected to have higher melting points than those
with flexible molecules
On melting, polymers with stiff backbones have lower conformational entropy changes
than those with flexible backbones.
Chain flexibility is enhanced by the presence of such groups as –O– and –(COO)– and by
increasing the length of (–CH2–) units in the main chain.
Insertion of polar groups and rings restricts the rotation of the backbone and consequently
reduces conformational changes of the backbone
Copolymerization
The effect of colpolymerization on Tm depends on the value of compatibility of comonomers.
 If the comonomers have similar specific volumes, they can replace each other in the crystal lattice
(isomorphous systems), and Tm will vary smoothly over the entire composition range.
 If the copolymer is made from monomers each of which forms a crystalline homopolymer, the
degree of crystallinity and the crystalline melting point decreases as the second constituent is added
to either of the homopolymers.
The Tm of the copolymer (in the second case);
1
1
R
 
ln X
Tm Tm H m
where;
H m  heat heat of fusion
X  mole fraction of the homopolymer orcrystallizing (major) component
Block and graft copolymers with sufficiently long homopolymer chain sequences crystallize
and exhibit properties of both homopolymers and have two melting points, one for each type
of chain segment.