CONTENT:

 Introduction
 Classification
 Polymerization
 Molecular weight determination
 Thermal characterization
 Pharmaceutical Applications
 Bio degradable polymers
 Application of biodegradable polymers
 References.

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Definition :
A polymer is a large molecule (macromolecule) composed
of repeating structural unit connected by covalent chemical
bonds. The small repeating units are called as monomers

Example:- Butadiene, poly-vinyl-chloride etc.

The word is derived from the Greek words (poly), meaning

"many"; and (meros), meaning "part“

 They are complex and giant molecules and are different

from low molecular weight compounds.

Macro-molecules’ are made up of much smaller molecules.

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 Imagine that a monomer can be 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-A-A-A-A-A-A-A-A-A-A

 In another kind of polymer, two different monomers might be

involved

 If the letters A and B represent those monomers, then the

polymer could be represented as:

-A-B-A-B-A-B-A-B-A-B-A-B-A-B-A-B-A-B-A-B-A-B-A-B-A-B-A

 A polymer with two different monomers is known as a

copolymer.

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 CHARACTERISTICS OF AN IDEAL POLYMER

 Should be versatile and possess a wide range of

mechanical, physical, chemical properties.

 Should be non-toxic and have good mechanical strength

and should be easily administered.

 Should be inexpensive.

 Should be easy to fabricate.

 Should be inert to host tissue and compatible with

environment.
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A. CLASSIFICATION BASED ON THE PROPERTIES AND
CHARACTERISTICS
 Natural and Synthetic Polymers.
 Organic and Inorganic Polymers.
 Thermoplastic and Thermosetting Polymers.
 Plastics, Elastomers, Fibers, and Liquid Resins

B. BASED ON BIO-STABILITY:
 Bio-degradable
 Non Bio-degradable
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C. BASED ON OF INTERACTION WITH WATER:
 Non-biodegradable hydrophobic Polymers
E.g. polyvinyl chloride, polyethylene vinyl acetate
 Soluble Polymers E.g. HPMC, PEG
 Hydrogels E.g. Polyvinyl pyrrolidine

D. BASED ON POLYMERISATION METHOD:

 Addition Polymers E.g. Alkane Polymers
 Condensation polymers E.g. Polysterene and Polyamide
 Rearrangement polymers

E. BASED ON POLYMERIZATION MECHANISM:

 Chain Polymerization
 Step growth Polymerization 7
F. BASED ON CHEMICAL STRUCTURE:
 Activated C-C Polymer
 Polyamides, polyurethanes
 Polyesters, polycarbonates
 Polyacetals, Polyketals, Polyorthoesters
 Inorganic polymers
 Natural polymers

G. BASED ON OCCURRENCE:
 Natural polymers E.g. 1. Proteins-collagen, keratin,
albumin, 2. carbohydrates- starch,
cellulose
 Synthetic polymers E.g. Polyesters, polyamides

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1. Natural and Synthetic Polymers:
Natural polymers
 Polymers are very common in nature

 Some of the most widespread naturally occurring substances are

polymers Starch and cellulose are examples

 Green plants have the ability to take the simple sugar known as
glucose and make very long chains containing many glucose units.

 These long chains are molecules of starch or cellulose.

 If we assign the symbol G to stand for a glucose molecule, then

starch or cellulose can be represented as:
-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-

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 Natural polymers remains the primary choice of formulator
because
- They are natural products of living organism
- Readily available
- Relatively inexpensive
- Capable of chemical modification

 Moreover, it satisfies most of the ideal requirements of

polymers.

 But the only and major difficulty is the batch- to-batch

reproducibility and purity of the sample.

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Examples :
1) Proteins :
- Collagen : Found from animal tissue.
 Used in absorbable sutures, sponge wound dressing, as
drug delivery vehicles
- Albumin : Obtained by fabrication of blood from
healthy donor. Used as carriers in nanocapsules &
microspheres
- Gelatin : A natural water soluble polymer
 Used in capsule shells and also as coating material in
microencapsulation.

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Synthetic polymer
Polypropylene (PP)
Polyvinyl chloride (PVC)
Polyvinylidene chloride (PVdC)
Polystyrene (PS)
Polymethyl methacrylate (PMMA)
Amino formaldehyde
Polyamides (Nylon)
Polyethylene terephthalate
Polytetrafluoroethylene
Cellulose acetate
Acrylonitrile butadiene styrene

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 2) Organic and Inorganic Polymers:

 A Polymer whose backbone chain is essentially made of carbon

atoms is termed an Organic polymer.
 Examples- cellulose, proteins, polyethylene, nylons.

 A Polymer which does not have carbon atom in their backbone

chain is termed as Inorganic polymer.
 Examples- Glass and silicone rubber

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 3) Thermoplastic and Thermosetting Polymer:
 Some polymer are soften on heating and can be converted
into any shape that they can retain on cooling.
 Such polymer that soften on heating and stiffen on cooling
are termed as `thermoplastic’ polymers.
 Ex. Polyethylene, PVC, nylon, sealing wax.

 Polymer that become an infusible and insoluble mass on

heating are called ‘thermosetting’ polymers.

 Ex. Melamine, Urea.

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4)Plastic, Elastomers, Fibers and Liquid Resins:

 A polymer is shaped into hard and tough utility articles by

application of heat and pressure, it is used as ‘plastic’
 Ex. PVC

 When vulcanized into rubbery products exhibiting good

strength and elongation, polymers are used as ‘Elastomers’
 ex. Natural rubber

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 Polymerization is a process of bonding monomer, or
“single units” together through a variety of reaction
mechanisms to form longer chains named Polymer.

 Addition polymerization
 Condensation polymerization

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Addition polymerization

 A carbon – carbon double bond is needed in the

monomer
 A monomer is the small molecule that makes up the
polymer.

H H
H H high pressure/trace O 2
n C C C C
catalyst
H H H H n
ethene
poly(ethene)
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 The polymer is the only product.
 Involves the opening out of a double bond.
 The conditions of the reaction can alter the properties
of the polymer.
 Reaction proceeds by a free radical mechanism.
 Conditions are high pressure and an oxygen initiator.
 Oxygen often used to provide the initial free radical.

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Condensation Polymerisation
 Involves 2 monomers that have different functional
groups.
 They also involve the elimination of water or another
small molecule.
 Hence the term condensation polymer.
 Monomer A + Monomer B  Polymer + small molecule
(normally water).
 Common condensation polymers include polyesters
(the ester linkage) and polyamides (the amide linkage
as in proteins).

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 The example here is terylene, a polymer of benzene-
1,4-dicarboxylic acid and ethane-1,2-diol.

O O
n HO C C OH + n HO CH2 CH2 OH
heat with
an acid
• hhhhhhhhhhhhhhhhhhh + nH2O
catalyst

O O
C C O CH2 CH2 O

poly(ethan-1,2-diyl benzene-1,4-dicarboxylate)

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1. Linear Polymers:
A polymer in which the molecules form long
chains without branches or cross-linked
structures.

Examples: nylon, polyester, PVC etc.

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2. Branched Polymer:
A polymer chain having branch points that
connect three or more chain segments.
Examples: polythene, glycogen, starch etc

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3. Cross linked Polymer:
Cross-links are bonds that link one polymer chain to
another. They can be covalent bonds or ionic bonds.

Examples: malamine formaldehyde resin etc

 Linear & Branched Polymers are know as thermoplastic

materials.

 Cross linked Polymer are know as thermosetting materials.

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 When polymers are fabricated, there will always be a
distribution of chain lengths.
 The properties of polymers depend heavily on the
molecule length.

 There are two ways to calculate the average molecular

weight:

a. Number Average Molecular Weight

b. Weight Average Molecular Weight

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a. Number Average Molecular Weight
 Molecular weight is determined by calculating the total
molecular weight of monomer and total number of
monomer.

Mn
NM i i

N i

 Mi- total molecular weight of monomer.

 Ni- number of monomer molecules.
 Mn- number average molecular weight.
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b. Weight Average Molecular Weight

 M - weight average molecular weight.

 Mi- total molecular weight of monomer.
 Ni- number of monomer molecules.
 Mw- weight molecular weight.

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 Thermal analysis of the polymers is the important
phenomenon to study the stability and degradation of
polymers.

Method :-
a. TGA
b. DSC
c. Thermo mechanical analysis

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THERMOGRAVIMETRICAL ANALYSIS (TGA)

• This method provides indication for thermal stability

and upper limit of thermal degradation where loss of
sample begins.

• This method only measures loss of volatile content from

the polymer.

• This method has limitation that it can not detect

temperature at chain cleavage takes place.

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Differential Scanning Calorimetry (DSC)

Parameters measured-
1. Glass transition temperature (Tg)
2. Crystalline melting point
3. Heat of fusion
4. Heat of crystallization

 It requires placing of reference and test sample

for the continuous monitoring in the heating
chamber.

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 The glass–liquid transition or glass transition is the reversible transition in
amorphous materials (or in amorphous regions within semicrystalline
materials) from a hard and relatively brittle "glassy" state into a viscous or
rubbery state as the temperature is increased.[1] An amorphous solid that
exhibits a glass transition is called a glass. The reverse transition, achieved by
supercooling a viscous liquid into the glass state, is called vitrification.
 The glass-transition temperature Tg of a material characterizes the range of
temperatures over which this glass transition occurs. It is always lower than the
melting temperature, Tm, of the crystalline state of the material, if one exists

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Major polymer transition

1. Glassy
2. glassy transition
3. rubbery plateau
4. Rubbery flow
5. Viscous flow

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Thermo Mechanical Analysis (TMA)

• This method is used for determination of deformation

of polymer sample as a function of temperature placed
on platform in contact with probe.

• It measures transition from glassy to a rubbery polymer

and gives idea about softening temperature.

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39
CRITERIA FOLLOWED IN POLYMER SELECTION

 The polymer should be soluble and easy to synthesis

 It should have finite molecular weight

 It should be compatible with biological environment

 It should be biodegradable

 It should provide good drug polymer linkage

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 Applications in Conventional Dosage
Forms
 Tablets :
- As binders. Examples: Acacia, Gelatin, Sodium alginate
- To mask unpleasant taste
- For simple and enteric coated tablets. Ex. HPMC, MC and HPMCP, CAP.
- Disintigrants. Ex. Starch
 Capsules
 - Gelatin/HPMC to prepare HGC/SGC
 Liquids :
- Viscosity enhancers. Ex. MC
- For controlling the flow
- Suspending and emulsifying agent. Ex. Gelatin
 Semisolids :
- In the gel preparation
- As base of the ointments
 In transdermal Patches

 For microencapsulation polymers are used.

- Examples: Ethyl cellulose, Gelatin, Acacia, Polyvinylpyrrolidone etc.
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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

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 Material progressively releasing dissolved or
dispersed drug, with ability of functioning for a
temporary period and subsequently degrade in the
biological fluids under a controlled mechanism, in to
product easily eliminated in body metabolism
pathway.

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Biodegradable polymers can be classified in two:

1. Natural biodegradable polymer

examples: xanthum gum, gaur gum, chitosan, chtin etc.

2. Synthetic biodegradable polymer

examples: Polyanhydrides, Poly(ß-Hydroxybutyric Acidc)
etc.

 Synthetic biodegradable polymer are preferred more than the

natural biodegradable polymer because they are free of
immunogenicity & their physicochemical properties are more
predictable &reproducible

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 ADVANTAGES OF BIODEGRADABLE
POLYMERS IN DRUG DELEVERY

 Localized delivery of drug

 Sustained delivery of drug

 Stabilization of drug

 Decrease in dosing frequency

 Reduce side effects

 Improved patient compliance

 Controllable degradation rate

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ROLE OF POLYMER IN DRUG DELIVERY
 The polymer can protect the drug from the physiological
environment & hence improve its stability in vivo.

 Most biodegradable polymer are designed to degrade within the

body as a result of hydrolysis of polymer chain into biologically
acceptable & progressively small compounds.
TYPES OF POLYMER DRUG DELIVERY SYSTEM:
 MICRO PARTICLES: These have been used to deliver
therapeutic agents like doxycycline.

 NANO PARTICLES: Delivery drugs like doxorubicin,

cyclosporine, paclitaxel, 5- fluorouracil etc

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 POLYMERIC MICELLES: Used to deliver therapeutic agents.

 HYDROGELS: these are currently studies as controlled release

carriers of proteins & peptides.

 POLYMER MORPHOLOGY: The polymer matrix can be

formulated as either micro/nano-spheres, gel, film or an
extruded shape.
The shape of polymer can be important in drug release
kinetics.

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DRUG RELEASE MECHANISM
The release of drugs from the erodible polymers occurs
basically by three mechanisms,

I. The drug is attached to the polymeric backbone by a

labile bond, this bond has a higher reactivity toward
hydrolysis than the polymer reactivity to break down.
II. The drug is in the core surrounded by a biodegradable
rate controlling membrane. This is a reservoir type
device that provides erodibility to eliminate surgical
removal of the drug-depleted device.
III. A homogeneously dispersed drug in the biodegradable
polymer. The drug is released by erosion, diffusion, or a
combination of both.

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 For specific site drug delivery- anti tumour agent

 Polymer system for gene therapy

 Bio degradable polymer for ocular, non- viral DNA, tissue

engineering, vascular, orthopaedic, skin adhesive &
surgical glues.

 Bio degradable drug system for therapeutic agents such as

anti tumor, antipsychotic agent, anti-inflammatory agent
and biomacro molecules such as proteins, peptides and
nucleic acids

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 Wound management
 Sutures

 Orthopedic devices
 Rods
 Screws Staples
 Ligaments
 Pins

 Tissue engineering

 Dental applications
• Guided tissue regeneration Membrane
• Void filler following tooth extraction
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 Govariker V. R., Viswanathan N. V., Sreedhar J., “Polymer
Science”, New age publications, 263 .

 Jain N.K., Controlled and novel drug delivery, CBS

Publisher,New delhi, 27-49.

 Martin A., Swarbrick J., Commarata A., Physical pharmacy,

K.M.varghese company, Bombay, 592-636.

 Biodegradable Polymer as drug delivery system; “Synthetic

polysaccharides”; edited by-Mark Chasin, Robert Langer Vol-
45; Page No-43-49,71-90,121-160. 51
THANK
YOU

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