POLYMERS

History of Polymers
▪ In 1811, Henri Braconnot did pioneer work on cellulose.
▪ In the nineteenth century vulcanization is improved.
▪ In 1907, Leo Baekeland created the first synthetic polymer which is Bakelite.
▪ In 1922, Hermann Staudinger proposed that polymers consisted of long chains o atoms held
by covalent bonds.
▪ Paul Flory did extensive work on addition polymerization, chain transfer and excluded
volume.

Henri Braconnot Leo Baekeland Hermann Staudinger Paul Flory

By SPT Paul Topham - Own work, CC BY-SA 4.0,
https://commons.wikimedia.org/w/index.php?curid=108853365
 History of Polymers
Hermann Staudinger (1881-1965)
Father of Macromolecular Chemistry

https://www.acs.org/content/acs/en/education/whatischemistry/landmarks/staudingerpolymerscience.html
Polymer
▪ the term “polymer” was derived
from the Greek word poly and
meros, which means many and
parts.
▪ associated polymers with the term
plastics or synthetic polymers. All
plastics are polymers, but not all
polymers are plastics.
Example: Grocery bags, water
bottles, telephones, seat covers
 Characteristics
▪ a large molecule composed of repeating small molecule units.
▪ a polymer is a high molar mass molecular compound made up of
many repeating chemical units.
▪ polymers can have a huge range or material properties based on
their functional groups, structure, and backbone.
▪ the functional group is what gives each polymer chain its
individual characteristics.
▪ difference between monomers can affect the properties of
polymer such as solubility, flexibility, or strength.
 CLASSIFICATION OF POLYMERS
1. Synthetic or Man-made polymers
that are synthesized in the
laboratory.
Example: polyethylene, polystyrene,
Dacron, and Lucite.

2. Natural or Biological polymer

that are found in nature.
Example: proteins, nucleic acids,
cellulose, and rubber.
 Structure of Polymers
▪ Substance that consist of large molecules is called
macromolecules that are made up of many repeating subunits
called monomers.
▪ Macromolecule formed by the covalent attachment of a set of small
molecule precursor or building block of polymers is termed
monomer.
▪ a monomer unit consists of a small carbon chain attached to a
specific type of functional group.
▪ The chemical structure of polymers is represented by the monomer
enclosed in a parenthesis. The number of repeating monomer units
is represented by the n.
Simple repeating unit of polymer is monomer

Homopolymer is a polymer made up of only one type of monomer.

Copolymer or heteropolymer is a polymer made up of two or more monomers.

By Gmrozz - Own work, CC BY-SA 4.0,

https://commons.wikimedia.org/w/index.php?curid=91667115
Structure:

Sample:
Monomer Polymer

Fig 1. Structure of monomer ethene and chemical structure of polyethene

Example:
Draw the structure of the polymer that can be produced
from the monomer propylene.
Sample Problem:
1. Draw the structural formula of the repeating unit of the following
polymers:
a. polypropylene
b. polyvinyl acetate
c. polyvinyl alcohol
Solution
1a. polymer : polypropylene
monomer: propylene (CH=CHCH3)

1b. polymer : polyvinyl acetate

monomer: vinyl acetate (CH2=CHOOCCH3)

1c. polymer : polyvinyl alcohol

monomer: vinyl alcohol (CH2=CHOH)
 COPOLYMERS
▪ Copolymers are categorized based on their structures.
▪ Those containing a single chain are known as linear copolymers
whereas those containing polymeric side chains are called
branched copolymers.
▪ In this process, two different monomers joined to form a polymer.
Synthetic rubbers are prepared by this polymerization.
▪ Nylon is an example of copolymer made from more than one type
of monomer.
 THE FOUR BASIC COPOLYMERS STRUCTURE
▪ Alternating copolymers – monomers are arranged in a regular,
alternating series.

▪ Block copolymers – have regions in the material where a single

monomer unit is repeated, interspersed
 THE FOUR BASIC COPOLYMERS STRUCTURE
▪ Radon copolymers – monomers are randomly combined.

▪ Graft copolymers – involve side chains of one polymer attached

to a backbone of a different polymer.
 Properties of Polymers
Physical Properties
▪ As chain length and cross-linking increases the tensile strength of
the polymer increases.
▪ Polymers do not melt; they change state from crystalline to semi-
crystalline.
▪ Glass transition temperature (Tg) is the temperature range where
polymer chain groups segmental motion.
▪ Melting Temperature (Tm) is the temperature range in which the
whole polymer chains become mobile.
▪ Tm is the temperature at which crystalline domains lose their structure, or
melt. As crystallinity increases, so does Tm.
▪ Tg is the temperature below which amorphous domains lose the structural
mobility of the polymer chains and become rigid glasses.

▪ Tm and Tg values for some common addition polymers are listed below.
▪ Note that cellulose has neither a Tm nor a Tg.
Chemical Properties
▪ Compared to conventional molecules with different side
molecules, the polymer is enabled with hydrogen bonding and
ionic bonding resulting in better cross-linking strength.
▪ Dipole-dipole bonding side chains enable the polymer for high
flexibility.
⮚ The flexibility of the polymer depends on the following:
1. the presence of stiffening groups incorporated in the
polymer backbone.
2. the presence of functional groups attached to the polymer
backbone.
▪ Polymers with Van der Waals forces linking chains are known to
be weak, but give the polymer a low melting point.
Optical Properties
▪ Due to their ability to change their refractive index with
temperature as in the case of Poly(methyl methacrylate) or
PMMA and Hydroxyethylmethacrylate or HEMA: Methyl
methacrylate or MMA, they are used in lasers for applications in
spectroscopy and analytical applications.
 TACTICITY
▪ From Greek word “taktikos” , of or relating arrangement or order
▪ Describes the stereochemistry of the repeat units in polymer chains
▪ The tacticity of a polymer affects the packing between molecules (crystallinity)
and this affects its physical properties such as the melting temperature,
mechanical strength, and elasticity.
Structure regularity
Isotactic > Syndiotactic > Atactic
Tacticity of Polypropylene
▪ When the monomer is less than symmetrical than ethylene, there is additional
variability that might result from the polymerization process.
 STEREOISOMERS OF POLYMERS
Isotactic
▪ R groups on the same side of the chain

▪ the side chain is arranged on one side of the backbone chain.

 STEREOISOMERS OF POLYMERS
Syndiotactic
▪ R groups alternate from side to side

▪ polymers where the side chain is arranged alternatively on both

sides of the backbone chain.
 STEREOISOMERS OF POLYMERS
Atactic
▪ R groups disposed at random

▪ polymers where the side chain is arranged randomly along the

backbone chain.
 COMPARISONS OF STEREOISOMER
Isotactic Syndiotactic Atactic
Has the highest Have better impact Soft and rubbery,
melting point, strength than amorphous, and
greatest crystallinity, isotactic relatively weak
superior mechanical Low density and low
properties tensile strength but
high degree of
flexibility.
Factors Influencing the properties of Polymers
▪ Polymer properties depend on the chemicals that the
polymer is made from and polymerization conditions that
ultimately set molecular architecture: chemical linkage
type, chain length, and the nature of the end groups.
▪ The type of the monomer-repeat unit that forms a polymer
has a strong effect on polymer properties.
 DIMENSIONS OF A POLYMERIC CHAIN
▪ A polymer chain is built-up
from hundreds to many
hundreds of thousands of
monomer units, which are
called “mer” units when joined
into a chain.
▪ Polymer chains are fractal
objects whose dimensionality
is determined by interactions Fig. 8.6. Polymer configuration (shown simplified in 2D, in reality, polymers
have 3D structure). (A) amorphous, (B) purely crystalline, (C) semi-crystalline.
between the monomeric units https://www.sciencedirect.com/topics/engineering/polymer-chain
and solvent molecules.
 POLYMER MOLECULAR WEIGHT (MW)
▪ A polymer's molecular ▪ MWpolymer = DP x MWMonomer
weight is the sum of the
atomic weights of
individual atoms that
comprise a molecule.
▪ It indicates the average
length of the bulk resin's
polymer chains.
▪ Not all polymer molecules
of a particular grade have
the exact same molecular
weight.
▪ Molecular Weight plays an important in Polymer properties
Table 1

Table 2
 Degree of Polymerization (DP)
▪ Indicates the number of repeating units strung together

Property: Molecular Weight (MW) Relationship

o Oligomers - short chains (low DP)
o Polymers – longer chains (high DP)
o High DP required to develop useful properties
Sample Problem:
1. Polyethylene (C2H4) with average DP of 1000 and has the
average molecular weight of 28 g/mol. Calculate the
molecular weight of the polymer.

Given: Solution:
DP = 1000 MWpolymer = DP x MWMonomer
MW = 28 g/mol MWpolymer = (1000)(28 g/mol)
Find: MW polymer MWpolymer = 28 000 g/mol
SEATWORK:
1. Calculate the degree of polymerization, if the molecular weight
of Tetrafluoroethylene (C2F4) is 120 000 g/mol and the molecular
weight of the monomer is 100 g/mol.
 Flow Behavior of Polymers
1. VISCOSITY
▪ The viscosity of a polymer is always larger than that of the
corresponding monomer and increases rapidly with increasing
molecular weight (number of repeat units). This is due to entanglement
and intermolecular forces between polymer chains.
2. NEWTONIAN FLUIDS
▪ are fluids in which the viscosity is independent of the shear strain rate.
Most simple liquids like low molecular solvents, monomers, liquid
metals etc. obey Newton's law of viscosity.
3. NON-NEWTONIAN FLUIDS
▪ Polymer solutions, dispersions, and melts are usually non-Newtonian
liquids. Their viscosity depends on the applied shear rate.
FLOW BEHAVIOR OF POLYMERS
 POLYMERIZATION
▪ The process of reacting monomer molecules together in a chemical
reaction to three-dimensional network or polymer chain is known as
polymerization.
▪ The reaction by which monomers are linked together

Fig 2 Polymer formation during a polymerization reaction, large number of monomers become connected by covalent bonds to form a single long molecule, a polymer.
• https://chem.libretexts.org/Courses/Prince_Georges_Community_College/General_Chemistry_for_Engineering/
EXAMPLE: The polymerization of ethane to polyIethene)

SOME POLYMERS AND THEIR MONOMERS

▪ Polypropylene, also known as polypropylene, is made up of monomer propene.
▪ Polystyrene is an aromatic polymer, naturally transparent, made up of monomer
styrene.
▪ Polyvinyl chloride (PVC) is a plastic polymer made of monomer vinyl chloride.
▪ The urea-formaldehyde resin is a non-transparent plastic obtained by heating
formaldehyde and urea.
▪ Glyptal is made up of monomers ethylene glycol and phthalic acid.
▪ Bakelite or polyoxybenzylmethylenglycolanhydride is a plastic which is made up of
monomers phenol and aldehyde.
SYNTHETIC POLYMERS ARE CREATED BY MEANS OF:
a. Addition polymerization
b. Condensation polymerization
TYPES OF POLYMERIZATION REACTIONS:
1. ADDITION POLYMERIZATION
▪ Monomers react to form a polymer without net loss of atoms.
▪ This is also called as chain growth polymerization.
▪ This involves the breaking of double or triple bonds, which are used to
link monomers in chain.
Examples : polyethene, polypropylene, polyvinyl chloride

Fig 3. Ethane molecules linking together to form polyethylene

Polyethene
▪ Formed from monomer unit ethene and is used in making flexible
bottles, packaging, toys, films, sheets, and insulation for electric
wires.
Polypropylene
▪ Formed from monomer unit propene. It is denser, stiffer, and
harder than polyethene because of the added methyl group.
Polyvinylchloride (PVC)
▪ Used in pipes, flooring, garden hose, and raincoat, it is formed
from the monomer units vinyl chloride.
SUPRAMOLECULAR POLYMERS
▪ Supramolecular polymers are a kind of polymers whose
monomeric units hold together via highly directional and reversible
non-covalent interactions.
 MOLECULAR ARCHITECTURE
CLASSIFICATION OF POLYMERS BASED ON THE STRUCTURE OF THE
MONOMER CHAIN
This category has the following classifications:

Fig. 5 Basic Polymer Structure

A. Linear Polymers
▪ The structure of polymers containing long and straight chains fall
into this category.

Fig. 6 Structural properties of linear polymers

A. Linear Polymers
▪ The structure of polymers containing long and straight chains fall into this
category.
▪ The long chains are typically held together by the weaker van der Waals or
hydrogen bonding.
▪ These bonding types are relatively easy to break with heat, linear polymers are
typically thermoplastic.
▪ Heat breaks the bonds between the long chains allowing the chains to flow
past each other, allowing the material to be remolded.
▪ Upon cooling the bonds between the long chains reform, i.e., the polymer
hardens.
Example: High Density Polyethylene (HDPE), PVC, Electric cables Nylon, Cotton
B. Branched-chain Polymers
▪ These shorter chains can interfere with efficient packing of the
polymers, branched polymers tend to be less dense than similar
linear polymers.
▪ The short chains do not bridge from one longer backbone to
another, heat will typically break the bonds between the branched
polymer chains and allow the polymer to be a thermoplastic,
although there are some very complex branched polymers that
resist this ‘melting’ and thus break up (becoming hard in the
process) before softening, i.e., they are thermosetting.
Example: Low-Density Polythene (LDPE)
C. Cross-linked Polymers
▪ They are composed of bifunctional and trifunctional monomers. They
have a stronger covalent bond in comparison to other linear polymers.
▪ This resemble ladders. The chains link from one backbone to another.
▪ Crosslinked polymers are tied together via covalent bonding. This
much stronger bond makes most crosslinked polymers thermosetting,
with only a few exceptions to the rule: crosslinked polymers that
happen to break their crosslinks at relatively low temperatures.
Example: Rubber, Bakelite, and melamine
D. Networked polymers
▪ These are complex polymers that are heavily linked to form a complex
network of three-dimensional linkages.
Addition Polymers Samples:
1. Low-Density Polyethylene 2. Polyvinyl Chloride
(LDPE)
3. High-Density Polyethylene 4. Ultra-High Molecular-Weight
(HDPE) Polyethylene (UHMWPE)
 Natural Rubber and Synthetic Rubber
1. Natural Rubber from the Hevea 2. Vulcanized Rubber (Synthetic
bransiliensis tree or rubber tree. Rubber): Rubber with short chains of
sulfur atoms that bond together the
polymer of natural rubber.
TYPES OF POLYMERIZATION REACTIONS:
2. CONDENSATION POLYMERIZATION
▪ Involves monomers reacting together and releasing a small
molecule in the process. The small molecule is commonly water.
▪ Also known as dehydration reaction in which two monomers react
with the concurrent loss of water
Example: polyster (Dacron); polyamide (Nylon 66, Kevlar);
polyurethane (Spandex)

Example: formation of amide links and loss of water

Monomers

• First unit of polymer + H2O

Polyster
▪ Formed via condensation reaction between diol and diacids,
producing water as by product.
Polyamide(Nylon)
▪ Formed by the condensation reaction of a diacid and
diamine. Water is a by-product.
 Condensation Polymers Sample
1. Polyethylene Terephthalate 2. Kevlar
(PETE)
3. Nylon

Fig. 7 Supramolecular structure of nylon

Source: 2003@ Thomson-Brooks/Cole
QUIZ #1.
1. Draw the structural formula of monomers used to prepare the following
polymers:
a. polyethylene
b. polyvinylchloride
c. polystyrene
2. Use your understanding on polymerization to complete the table below
Name of Name of Polymer Formula of Formula of the polymer Polymer
Monomer the indicating the three formula
monomer repeated units
1. Ethene
2. Propene
3. Polychloroethene
3. Classify the following structures shown below as isotactic, syndiotactic and
atactic.
4. Writing the repeating unit of the condensation polymer obtained by combining
HOOCCH2CH2COOH and H2NCH2CH2NH2. Identify the amide linkage.

5. Draw the structure of the repeating unit of the condensation polymer obtained
from reacting terephthalic acid with ethylene glycol.
 CLASSIFICATION BASED ON MOLECULAR FORCES
1. Elastomers: These are rubber-like solids weak interaction forces are
present.
Example: Rubber.
2. Fibres: Strong, tough, high tensile strength and strong forces of interaction
are present.
Example: Nylon -6, 6.
3. Thermoplastics: These have intermediate forces of attraction.
Example: Polyvinyl chloride.
4. Thermosetting polymers: These polymers greatly improve the material’s
mechanical properties. It provides enhanced chemical and heat resistance.
Example, Phenolics, Epoxies, and Silicones.
 CLASSIFICATION OF POLYMERS
1. Thermoplastics or Thermo-
softening plastics
▪ Polymers that can be melted and
reshaped by applying heat and pressure.
▪ The ability to melt at reasonable
temperatures becomes a major
advantage.
▪ The fact that the material softens or melts
when heated allows shaping it into desired
form.
▪ In a thermoplastic polymer, chains interact
only through intermolecular forces.
Example: Polyethylene (PE), Polypropylene
(PP), and Polystyrene
The thermoplastic category of polymers is further categorized into Amorphous
and Crystalline polymers per the figure below:

Fig 8. Thermoplastic Category of Polymers

https://aipprecision.com/thermoplastics-vs-thermosets/
 CLASSIFICATION OF POLYMERS:
2. Thermosets or Thermosetting
plastics
▪ Polymers that readily undergo degradation
upon application of heat and pressure before
they melt and reshaped.
▪ Thermosetting polymers maintain their shape
and strength when heated.
▪ The presence of crosslink or covalent bonds
that attached one polymer main chain to
another polymer main chain is a common
characteristic if thermosetting polymers.
Example: Vulcanized rubber, Epoxy (Bisphenol-
A diglycidyl ether epoxy), Polyurethane.
COMMERCIAL USES OF POLYMERS
 BIODEGRADABLE POLYMERS
▪ The polymers which are degraded
and decayed by microorganisms
like bacteria are known as
biodegradable polymers.
▪ These types of polymers are used
in surgical bandages, capsule
coatings and in surgery.
Example: Poly(3-hydroxybutyrate-
co-3-hydroxyvalerate) or PHBV

https://www.researchgate.net/figure/Classification-of-biodegradable-
plastics_fig1_333778364
RECYCLING CODES FOR THE COMMONLY
USED PLASTICS
A Guide to Common Household Plastics

https://www.chemeurope.com/en/infographics/107/a-guide-to-common-
household-plastics.html
 TYPES OF POLYMERS
Based on the type of the
backbone chain, polymers can
be divided into:
▪ Organic Polymers: Carbon
backbone.
▪ Inorganic Polymers:
Backbone constituted by
elements other than carbon.
https://byjus.com/jee/polymers/
Naturally- occurring polymers
❑naturally-occurring polymers are ubiquitous in nature. These
natural polymers perform certain tasks in every living organism
such as animal and plants that are vital for their existence such as
structural support and some biological.
1. cellulose
2. starch
3. chitin
4. proteins
 CELLULOSE
❑ a linear polymer of glucose, the
major structural component of
plant cell walls.
❑ the most abundant organic
polymer material on earth.
❑ Cellulose is the most common
organic material on earth.
❑ It is also a primary constituent
of wood and paper.

https://www.researchgate.net/figure/Sources-of-cellulose_fig3_315500698
 COTTON
▪ a soft, fluffy staple fiber that grows
in a boil, or protective case, around
the seeds of the cotton plants of the
genus Gossypium in the mallow
family Malvaceae.
▪ The fiber of cotton is almost pure
cellulose, and can contain minor
percentages of waxes, fats, pectins,
and water.

Long Strands of Cellulose+ Hydrogen Bonds

 Polymers in Biology
Starch

DNA

Proteins

Sugar
 STARCH
❑the polymeric form of
glucose that serves as
the plant’s major energy
storage.
❑the starch structure
comprises of the linear
amylose and the
branched amylopectin.

https://www.researchgate.net/figure/Some-sources-of-starch_fig5_315500698
 CHITIN
▪ a long-chain polymer of N-
acetyglucosamine, is a derivative
of glucose. It is a primary
component of cell walls in fungi,
the exoskeletons of arthropods
and the scales of fish and
lissamphibians.
▪ deacetylation of chitin produces
chitosan
▪ chitosan is used in food
applications; it also has an
antibacterial and antifungal
properties.
https://www.researchgate.net/figure/Chitin-and-chitosan-sources-and-reported-uses_fig1_320845033
 PROTEINS
▪ a polymer composed
of amino acids linked
together by peptide
bonds.
Example: DNA, silk
from the cocoon of
silkworm, collagen

Phosphate-sugar backbone holds the

DNA macromolecule together
Carbohydrates

76
 INORGANIC POLYMERS
▪ Polymers with a skeletal structure that does not include carbon atoms
in the backbone.
▪ polymers containing inorganic and organic components are sometimes
called hybrid polymers, and most so-called inorganic polymers are
hybrid polymers.
▪ one of the best known examples is polydimethysiloxane, otherwise
known commonly as silicone rubber.
▪ inorganic polymers offer some properties not found in organic materials
including low-temperature flexibility, electrical conductivity, and
nonflammability.
▪ inorganic polymers in aqueous solutions are good conductors of
electricity, this is because they have high ability to ionize and this
makes them better conductors.
 INORGANIC POLYMERS
▪ the melting and boiling points of inorganic polymers is lower than
that of organic polymers.
▪ inorganic polymers are highly soluble in common organic solvents
and water.
▪ the term inorganic polymer refers generally to one-dimensional
polymers, rather than to heavily crosslinked materials such as
silicate minerals.
▪ inorganic polymers with tunable or responsive properties are
sometimes called smart inorganic polymers.
▪ a special class of inorganic polymers are geopolymers, which may
be anthropogenic or naturally occurring.
 Polyphosphazene Applications
http://www.personal.psu.edu/hra1/applications1.htm
REACTIONS IN POLYMERS
Addition Polymers: Radical Polymerization
▪ Radical –molecules with one or more unpaired e-
Example: Methane, CH4

2. Ethene, H2C=CH2
Polymer Classification by Mode of Assembly
Chain-Growth Polymers
▪ formed under conditions in which the monomers do not react directly with
each other, but rather, each monomer is added to the growing chain one at a
time. The growing polymer chain generally has only one reactive site, called
a growth point, and the monomers attach to the chain at the growth point.
Polymer Classification by Mode of Assembly
Step-Growth Polymers
▪ formed under conditions in which the individual monomers react
with each other to form oligomers, which are then joined together
to form polymers.
▪ occurs when difunctional monomers are used.
▪ all monomers and oligomers have two growth points.
Condensation Polymer
Polyethylene terephthalate (PET)
Nylon 6,6
Application in Industry
Preparation of Rayon
https://www.youtube.com/watch?v=Co4tBVGVxbQ
Synthesis of Nylon
https://www.youtube.com/watch?v=3ndzkma1V_k
CAMBRIDGE
Nylon Synthesis
https://www.youtube.com/watch?v=4_EEndIUB-c
Supplemental Video Learning:

• How Plastic Bottles Are Recycled Into Polyester -

YouTube
SEATWORK: Synthesis of Nylon-6,10

1. Draw the structures of the precursor materials to prepare Nylon-6,10

Name Structures

Sebacoyl Chloride

1,6-Hexanediammine

2. Write an equation showing the reaction of sebacoyl chloride and 1,6-

hexanediammine to form Nylon-6,10.