he reaction involving combination of two or more monomer units to form a long chain polymer is termed as polymerization. These are widely used as Pharmaceutical aids like suspending agents, Emulsifying agents, Adhesives, Coating agents, Adjuvants etc.

1. POLYMER SCIENCE
POLYMER
EVERYWHERE
1
Dr. Manoj M. Nitalikar
Department of Pharmaceutics
Rajarambapu College of Pharmacy,
KASEGAON

2. CONTENTS
 Introduction.
 Types and applications of polymers.
 Polymerization Reactions.
 Methods of Polymerization.
 Characterization of Polymers.
 References.
2

3. INTRODUCTION
POLYMER Greek word polu, “many”; and meros, “part”.
Polymer - Large molecule (macromolecule) composed of
repeated structural units connected by covalent chemical bonds.
The small repeating units - monomers.
For example: A monomer is represented by the letter A. Then a
polymer made of that monomer would have the structure:
-A-A-A-A-A-A-A-A-A-A-A-A-A-A-A-A-
3

4. INTRODUCTION
When two different monomers are involved.
For example: If monomers are represented by the letters A and
B, then the polymer could be represented as:
-A-B-A-B-A-B-A-B-A-B-A-B-A-B-A-B-
A polymer with two different monomers is known as a
copolymer.
Molecular Weight of typical monomer, Mo ≈ 50 – 100.
MW of polymer, M = nPMo ≈ 1,000-1H106 or more,
where n is number of repeating units.
4

5. CLASSIFICATION OF POLYMERS
BY OCCURRENCE:
A.Naturally Occurring Polymers
Proteins
Nucleic acids
Cellulose
Rubber
B. Synthetic Polymers
Nylon
Dacron
Polythene
5

6. CLASSIFICATION OF
POLYMERS
BY CHEMICAL COMPOSITION:
Homopolymers: contain a single kind of monomer
Copolymers: contain more than one kind of monomer
(a) random (b) alternating (c) block (d) graft
-A-A-A-A-A-A-A-A- Homopolymer
-A-B-B-A-B-A-A-B- Random copolymer
-A-B-A-B-A-B-A-B- Alternating copolymer
-A-A-A-A-B-B-B-B- Block copolymer
-A-A-A-A-A-A-A-A- Graft copolymer
B-B-B-B-B-
6

7. CLASSIFICATION OF POLYMERS
BY CHAIN STRUCTURES:
Linear (e.g. High Density PE)
Branched (e.g. Low Density PE)
Network
(e.g. Cross-linked polymers;
elastomers)
7

8. CLASSIFICATION OF POLYMERS
BY PROCESSING PROPERTIES:
Thermosetting Polymers: Get decomposed when heated; can not be
reformed or recycled. Presence of extensive crosslinks between long
chains induce decomposition upon heating and renders thermosetting
polymers brittle. (network polymer)
e. g. Epoxy and Polyesters
Thermoplastic Polymers: Melt and flow when heated; easily reshaped
and recycled. Presence of long chains with limited or no crosslinks.
(linear or branched polymer)
e.g. Polyethylene, Polyvinylchloride
8

9. CLASSIFICATION OF POLYMERS
BY PROCESSING PROPERTIES:
Elastomers: Intermediate between thermoplastic and thermosetting
polymers due to presence of some crosslinking.
Can undergo extensive elastic deformation.
e. g. Natural rubber, Silicone
9

10. CLASSIFICATION OF
POLYMERS
BY TYPE OF DRUG
Polymer Type Examples Drug Type
Biodegradable Poly(2-hydroxyethyl methacrylate) Lipophobic
Poly(vinyl pyrrolidone) and
Poly(lactic acid) Hydrophilic
Poly(glycolic acid)
Collagen
Swellable Ethylene/Vinyl Alcohol
Bioadhesive Polycarbophil
Fibronectin segment
Ion-exchange Polystyrene sulfonic acid
Hydrophobic Polydimethylsiloxane Lipophilic
Polyethylene
Ethylene/Vinyl acetate
Polyurethane 10

11. APPLICATIONS
 Agriculture and Agribusiness Polymeric materials are used in
and on soil to improve aeration, provide mulch, and promote
plant growth and health.
 Medicine Many biomaterials, especially heart valve
replacements and blood vessels, are made of polymers like
Dacron, Teflon and polyurethane.
 Consumer Science
Plastic containers of all shapes and sizes are light weight and
economically less expensive than the more traditional
containers. Clothing, floor coverings, garbage disposal bags,
and packaging are other polymer applications.
11

12. APPLICATIONS
 Industry
Automobile parts, windshields for fighter planes, pipes, tanks,
packing materials, insulation, wood substitutes, adhesives,
matrix for composites, and elastomers are all polymer
applications used in the industrial market.
 Sports
Playground equipment, various balls, golf clubs, swimming
pools, and protective helmets are often produced from
polymers.
12

13. APPLICATIONS IN CONVENTIONAL DOSAGE
FORMS
 Tablets :
- As binders e.g. HPC, HPMC, MC, etc.
- To mask unpleasant taste e.g. Eudragit, HPMC, etc.
- For enteric coated tablets e.g. Eudragit, HPMC, CAP, etc.
 Liquids :
- Viscosity enhancers e.g. cellulose derivatives (sodium
CMC, methyl cellulose), etc.
 Semisolids :
- In the gel preparation
- In ointments
 In Transdermal Patches
13

14. APPLICATIONS IN CONTROLLED DRUG
DELIVERY
 Reservoir Systems
- Ocusert System
- Progestasert System
- Reservoir Designed Transdermal Patches
 Matrix Systems
 Swelling Controlled Release Systems
 Biodegradable Systems
 Osmotically Controlled Drug Delivery
14

15. APPLICATIONS
 The pharmaceutical applications of polymers range from
their use as binders in tablets.
 Viscosity and flow controlling agents in liquids, suspensions
and emulsions.
 Polymers are also used as film coatings to disguise the
unpleasant taste of a drug, to enhance drug stability and to
modify drug release characteristics.
15

16. POLYMERS CAN BE REPRESENTED BY
3-D solid models
3-D space models
2-D models
16

17. 17
MOLECULAR STRUCTURE
 The mechanical properties are also governed by the
structure of the polymer chains.
 They can be:
Linear: Network (3D):
Branched:
Cross-linked:

18. POLYMERISATION
 Reacting monomer molecules together in a chemical
reaction to form three-dimensional networks or
polymer chains.
The processes of polymerization are divided into two
groups:
 Condensation or Step-growth Reaction
 Polymerization Addition or Chain-Growth
Polymerization 18

19. POLYMERISATION
 Condensation or Step Growth Reaction:
Condensation occurs between two polyfunctional molecules to
produce one larger polyfunctional molecule, with elimination
Of water or by-products like methanol, ammonia or hydrogen
chloride.
Reaction continues until almost all or one of the reagents is used
up; an equilibrium is established which can be shifted at high
temperatures by controlling the amounts of the reactants and
products. 19

20. POLYMERISATION
 Condensation or Step Growth Reaction:
20
E. g. Nylon 66, a common polymeric clothing material, involving two
monomers, hexamethlene diamine and adipic acid, reacting to form
a dimer of Nylon 66.

21. POLYMERISATION
 Condensation or Step Growth Reaction:
.
21
Production of Polyethene terephthalate (PET)

22. POLYMERISATION
22
 Addition Polymerization or Chain-Growth Polymerization:
Molecules of same monomer or different monomers add together to
form a polymer
Polymerization.
Monomers are unsaturated compounds like alkenes, Alkadienes and
their derivatives. Polymerization take place through formation of
radicals or ionic species such as Carboanions or carbocations.
It involves the addition of monomer units of the growing chain by a
chain mechanism. At each stage a reactive intermediate is produced
for use in the next stage of growth of the chain.
 Chain-growth polymerization generally is fast, irreversible
and moderately to highly exothermic.

23. POLYMERISATION
23
 Addition Polymerization or Chain-Reaction Polymerization:
Polymerization of bifunctional monomer (A,B: two different
functional groups):
AB + AB → ABAB (or AB)2
)
AB + (AB)2
→ (AB)3
AB + (AB)3
→ (AB)4
(AB)2
+ AB)2
→ (AB)4
………
……..…
(AB)r
+ (AB)s
→ (AB)r+s

24. 24
Mechanisms of Chain-Growth Polymerization
Chain-growth polymerization can be classified as
radical, ionic and coordination polymerization,
depending on the type of initiation.
POLYMERISATION
 Addition Polymerization or Chain-Reaction Polymerization:

25. 25
Radical polymerization
An initiator is needed to produce the first radical and to
start the chain of addition reactions. The initiators are
Thermal decomposition, Photolysis, Redox reactions and
Ionizing radiation.
Common initiation reaction is thermal decomposition of
molecules containing weak bonds, e.g. peroxides (-O-O-) or
azo compounds (-N=N-). Formed radicals react with the
monomers. Once initiated, a chain will grow by repeated
additions of monomer molecules with simultaneous
creation of a new radical site. This propagation is very fast,
so very long polymer chains will form already in the
earliest stage of the reaction.
POLYMERISATION
 Addition Polymerization or Chain-Reaction Polymerization:

26. 26
POLYMERISATION
 Addition Polymerization or Chain-Reaction Polymerization:
Ionic polymerization
Initiator is an ion.
During chain growth, monomers continue to add to the
anionic chain end so the chain grows by two C-atoms at a
time. In both anionic and cationic polymerization, there is
no termination through combination of two chains because
the ionic chain ends, which have the charge, would repel
each other. Termination takes place by the addition of
water, alcohol, acids or amines. Without such additions the
chains keep growing until the monomer is exhausted and
the reaction stops.

27. 27
POLYMERISATION
 Addition Polymerization or Chain-Reaction Polymerization:
Coordination (Ziegler-Natta) Polymerization
The mechanism is poorly understood as it takes place on
surface of insoluble particle
Transition-metal catalysts are involved.
A growing polymer chain is coordinatively bound to a metal
atom that has another coordinative vacancy.
Branching will not occur through this mechanism since no
radicals are involved; the active site of the growing chain is
the carbon atom directly bonded to the metal.
e. g. High density polyethene

28. 28
MECHANISM DIFFERENCE: STEP-REACTION :
CHAIN-REACTION
Step Reaction Chain Reaction
Growth occurs throughout
matrix by reaction between
monomers, oligomers, and polymers
(coupling reactions)
Growth occurs by successive addition
of monomer units to limited number
of growing chains
DPa low to moderate DPa can be very high
Monomer consumed rapidly while
molecular weight increases
slowly
Monomer consumed relatively slowly,
but molecular weight increases
rapidly
No initiator needed; same
reaction mechanism throughout
Initiation and propagation
mechanisms different
No termination step; end groups
still reactive
Usually chain-terminating step
involved
Polymerization rate decreases
steadily as functional groups
consumed
Polymerization rate increase
initially as initiator units generated;
remains relatively constant until
monomer depleted
Dpa= average degree of polymerization

29. 29
BIODEGRADABLE POLYMERS
ITS APPLICATIONS IN PHARMACY
A “biodegradable” product has the ability to break
down, safely, reliably, and relatively quickly, by
biological means, into raw materials of nature and
disappear into nature.

30. 30
BIODEGRADABLE POLYMERS
ITS APPLICATIONS IN PHARMACY
Classification:
NATURAL POLYMERS
A)Proteins:
a.Collagen
b.Albumin
c.Gelatin
B) Polysaccharides:
a. Starch
b. Hyaluronic acid
c. Dextran
d. Alginic acid
e. Xanthan Gum
f. Guar Gum
g. Rosin
h. Inulin
i. Pectin
j. Amylose
k. Cyclodextrin

31. 31
BIODEGRADABLE POLYMERS
ITS APPLICATIONS IN PHARMACY
NATURAL POLYMERS
A)Proteins:
a.Collagen
Used in absorbable sutures, wound dressings and drug
delivery microspheres.
Advantages: Easy to isolate and purify in large quantities.
Biocompatible and non toxic profile.
Well established physiochemical, structural and
immunological properties.
Disadvantages:
Chances of triggering antigenic responses.
Poor mechanical strength.
Non reproducible delivery rates.

32. 32
BIODEGRADABLE POLYMERS
ITS APPLICATIONS IN PHARMACY
NATURAL POLYMERS
A)Proteins:
b. Albumin
Used in cell and drug microencapsulation. absorbable
sutures, wound dressings and drug delivery microspheres.
Advantages: Biodegradation into natural products.
Easy availability.
Absence of toxicity and antigenicity.

33. 33
BIODEGRADABLE POLYMERS
ITS APPLICATIONS IN PHARMACY
NATURAL POLYMERS
A)Proteins:
c. Gelatin
Used in cell and drug microencapsulation. absorbable
sutures, wound dressings and drug delivery microspheres.
Advantages: Easy availability.
Low antigen profile.
Low temperature preparation technique.
Poor binding to drug molecules.

34. 34
BIODEGRADABLE POLYMERS
ITS APPLICATIONS IN PHARMACY
a. Starch
b. Hyaluronic acid: Lubricant
c. Dextran: Plasma expander, Drug carrier
d. Alginic acid and salts: Injectable microcapsules for
neurogenerative and hormone deficiency disease.
e. Xanthan Gum
f. Guar Gum
g. Rosin
h. Inulin
i. Pectin
j. Amylose
k. Cyclodextrin
l. Chitosan: used in controlled release systems, Gel forming ability
at low pH. Favourable biological properties

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DEGRADATION MECHNISMS
An irreversible process leading to a significant change of the
structure of a material, typically characterized by a loss of
properties, such as integrity, molecular weight, structure or
mechanical strength, into a product easily eliminated by the
body metabolic pathway
Degradation may be by :
1)Chemical means
2)Physical means

36. REFERENCES
1. Brahmankar D.M, Jaiswal S.B, Biopharmaceutics and
pharmacokinetics A Treatise, Vallabh Prakashan, Ist
edition,
New Delhi:1995: 18-50.
2. Dissolution test for solid dosage forms(2.9.3), European
Pharmacopoeia, fifth edition, 228-230.
3. Dissolution test (2.5.2), Indian Pharmacopoeia, 2007, 179-182.
4. Dissolution testing (A158-A162), British Pharmacopoeia 1993.
5. William. L and Wilkins. Remington The science and practice of
pharmacy, 21st ed., Vol 1. p. 672-88
6. Ye. Lee, Herman Lam, Xue-Ming zhary . Chung Chow Chan.
Analytical method validation and instrument performance
verification. Wiley-inter science US; 2004.p. 55 42
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