mainly biodegradable polymer.

1. POLYMER SCIENCE
Presented by
Arantha j joseph
First year Mpharm
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2. Contents
• Introduction
• Definition
• Classification
• Application
• Polymers as thickening agent
• Viscosity
• Solvent selection
• Fabrication technologies
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3. 1. INTRODUCTION
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 A word polymer is a combination of two Greek words,
“Poly” means “many” and “Meros” meaning “parts or units”.
A polymer is a large molecule of which is formed by
repeated linking of the small molecules called “monomers”.
More monomer molecules joined in units of long polymer.
n(CH2-CH2) (-CH2-CH2-)n
ethylene polyethylene

4. 2. DEFINITIONS
4
 Polymer science or macromolecular sciences is a subfield of material
science concerned with polymers.
 Polymer sciences has been the backbone for the development of new
formulations.
 Development of several applications in pharmaceutical sciences.
 Monomer - is the smaller molecule(s) that are used to prepare a
polymer.
 Polymerization : The process of linking the repeating units (monomers)
is termed as polymerization

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 Classification based on SOURCE.
 Classification based on BACKBONE.
Classification based on STRUCTURE.
 Classification based on POLYMERISATION.
3. CLASSIFICATION

6. 1.Classification based on SOURCE
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1. Natural polymers:- polymer that results from only raw materials that
are found in nature.
Example:- Proteins, Cellulose, Starch, Rubber.
Protein based: eg: albumin collagen, gelatin..
polysaccharides : eg: agrose, alginate, chitosan, dextran..
2. Synthetic polymers
a. Biodegradable
Polyesters : polylatic acid, polyglycolic acid, polyhydroxy butyrate.
 polyanhydrides : poly sebacic acid, poly adipic acid, poly
terphthalic acid

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They are degraded in the body
to the simple molecules like
water and CO2 which are easily
eliminated in the urine.
 Mainly used for parental drug
delivery system and can also be
used for oral drug delivery
system like liposomes,
nanoparticles, microspheres etc.
Eg:- poly(glycolic acid)etc….
They are non bio degradable
in the body.
Used only for oral
administration .
They cannot be used for
parental drug delivery of
drugs.
Eg:- ethyl cellulose, methyl
cellulose etc.
Biodegradable V/S Non Biodegradable

8. 2.Classification based on BACKBONE
Carbon chain backbone: eg: polyethylene,polypropylene,pvc,
pvp, polystyrene.
Hetrochain backbone: polyethylene oxide, polypropylene
oxide.
cellulose , amylose, pectinic acid.
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9. 3.Classification based on structure
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1.Linear polymers:- consist of long and straight chains.
Eg:- pvc
2.Branched chain polymers:- contain linear chains having
some branches,
e.g., low density polymer.
3.Cross linked chain polymers:- formed from bi-
functional and tri-functional monomers and contain
strong covalent bonds
e.g. bakelite, melamine.
4.3Dnetwork

10. 4. Classification based on polymerization
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1. Addition polymers
Formed by the repeated addition of monomer molecules possessing double or triple
bonds.
n(CH2=CH2) -(CH2 -CH2 )-
Ethylene polyethylene
2. Condensation polymers
Formed by repeated condensation reaction between two different bi-functional or tri-
functional monomeric units.
eg: nylon 6, 6, nylon 6.
n(H2N(CH2)6 NH2) + n(HOOC(CH2)4COOH) NH(CH2)6NHCO(CH2)4CO-]n nH2O
(Nylon 6:6)

11. CHARACTERISTICS OF IDEAL POLYMER
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1) It should be versatile.
2) It should possess a wide range of mechanical, physical
properties.
3) It should be non-toxic
4) should be easily administered.
5) It should be inexpensive
6) Easy to fabricate.
7) It should be inert to host tissue.

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MECHANISM OF DRUG RELEASE FROM POLYMER
 There are three primary mechanisms by which active agents
can be released from a delivery system: namely,
Diffusion,
Degradation,
Swelling .
 Diffusion occurs when a drug or other active agent passes
through the polymer that forms the controlled-release device.

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 The diffusion can occur on a macroscopic scale as through pores in
the polymer matrix or on a molecular level, by passing between
polymer chains.
 In this design, a reservoir whether
 solid drug,
 dilute solution,
 highly concentrated drug solution
 within a polymer matrix is
surrounded by a film or membrane of
a rate-controlling material.
 The diffusion rate of the active agent
can be kept fairly stable throughout
the lifetime of the delivery system.

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The system shown in Figure (a) is representative of an implantable or oral reservoir
delivery system, whereas the system shown in (b) is transdermal system.

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BIO DEGRADATION OF POLYMERS
 Bio degradation is the chemical changes that alter the molecular weight
or solubility of the polymers.
 Bio erosion may refer to as physical process that result in weight loss of
a polymer device.
 The erosion of polymers basically takes place by two methods:-
1. Chemical erosion
2. Physical erosion

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CHEMICAL EROSION
Bio erosions through chemical mechanisms are explained below-
Mechanism-I
It describes the degradation of water soluble macromolecules that
are cross-linked to form three-dimensional network
Degradation in these systems can occur by
 Type (1A)- Degradation occur at crosslinks to form soluble backbone
polymeric chains. It provides high molecular weight, Water soluble
fragments.
 Type (1B)- Degradation occur to form water-soluble fragments. Such
type provides low molecular weight, water soluble oligomers and
monomers.

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 Mechanism-II
Describes the dissolution of water insoluble macromolecules with
side groups that are converted to water insoluble polymers as a result of
ionization, Protonation or hydrolysis of the groups.
 Molecular weight remains unchanged.
 Materials showing this type of erosion include
Cellulose acetate derivatives,
Co-polymers of maleic anhydride.

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 Mechanism-III
Describes the degradation of insoluble polymers with liable
bonds. It forms low molecular weight, water soluble molecules.
 Polymers undergoing this type of erosion include
Poly(lactic acids)
Poly(glycolic acid) and their co-polymers etc.

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PHYSICAL EROSION
 The physical erosion mechanisms can be characterized as
heterogeneous or homogeneous.
 Most polymers undergo homogenous erosion that means the hydrolysis
occur at even rate through out the polymeric matrix.
 loss of integrity of the matrix or polymer.
 In heterogeneous erosion, also called as Surface Erosion. The polymer
erodes only at the surface and maintains its physical integrity as it
degrades.
 Highly crystalline polymers tend to undergo heterogeneous erosion.

20. DIFFERENT TYPES OF BIODEGRADABLE POLYMERS
1. Lactide / Glycolide Polymers.
2. Polyanhydrieds.
3. Poly Caprolactone.
4. Poly Orthoesters.
5. Poly Phosphazenes.
6. Pseudo Poly Amino Acids.
7. Natural Polymers.
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21. 1. Lactide/ Glycolide Polymers
• Widely used
• Bio compactable
• Predictable biodegradation kinetics
• Ease of fabrication
• A broad spectrum of applicability is obtained by manipulating 4
variables
• Co monomer ratio, monomer stereochemistry, polymer molecular
weight and polymer chain linearity.
• Crystalinity and water uptake key factor for determining rate of in
vivo degradation.
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22. • Solubility depends on type of monomers present.
• Lactide polymers show solubility in org solvents.
Bio degradation
• polymer chains are cleaved by hydrolysis monomeric acid
eliminates
Krebs cycle
Bio erosion of Lactide Occours with no enzymatic involvement.
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23. Biodegradation of lactide/glycolide polymers
Poly[l-Lactide]
18-24
Poly[dl-lactide]
12-16
Poly[glycolide]
2-4
50::50[dl-lactide-co-
glycolide]
2
85::15[dl-lactide-co-glycolide]
5
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24. 2. POLY ANHYDRIDES
OH-(-C-R-C-O-)n-H
O O
Degrade from the surface.
To maximize control over the release process.
increased degradation by copolymerization with sebacic acid.
[800]
eg:-bis carboxyphenoxypropane polymer.
Degrade rapidly in basic media.[100 days in ph 10]
Acidic media [3 years]
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25. • Cortisone acetate incorporated into several poly anhydrides
Rate of release
• Poly[terepthalic acid] poly[terepyhalic acid –sebacic acid] is
50::50.
• Eg formulation containing macromolecules like insulin in
poly anhydride matrices.
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26. 3. Poly carpolactone an its copolymers
• Carpolactone ring opening polymerization
• Suitable for long term drug delivery more than one year.
• Homopolymer degrade slowly compared to polyglycolic acid and
polyglycolic acid-co-lactic acid.
• Polymerization of carpolactone can affected by four mechanism.
• Anionic, cationic, coordination and radicle.
• Imp in the permeability and degradability of polymers.
• Eg: steroids, tetracycline's,
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27. 4. POLY[ORTHO ESTERS]
• Acid labile linkages in their backbone. Manipulation of
hydrolysis rate .
Incoorpation
acidic /basic excipients
Though it is acid sensitive a base is used
to neutralize and maintain hydrolysis
under control.
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28. • Hydrolysis is complicated
• Acid catalysis hydrolysis proceeds with the initial protonation of an
alkoxy oxygen followed by bond cleavage involving exocyclic or
endocyclic alkoxy gp.
• Incorporation of <1%.mol of 9,10dihydroxy stearic acid into the
polymer accelerate polymer erosion.
• Long term surface erosion is desired interior of the device is stabilized
by the use of basic excipients like Mg(OH)2
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Mg(OH)2
+drug
Mg(OH)
2
+drug

29. 5. POLYPHOSPHAZENES
• Hydrolytic stability/instability is determined by the change in side gp.
• Long chain backbone altering P and N
• Side gp attached to each P.
• Molecular structural change is by macromolecular substitution
reaction.
Amphiphilic Phosphazenes
• Attachment of hydrophilic and hydrophobic side gp.
• Eg. Trifluroethoxy and methyl amino gp
• Varied surface property,semipermiability.
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30. •Polyphosphazenes as hydrogels
• Intra ocular lens
• Soft tissue prosthesis
• Hydrophilic coating for biomedical devices.
Water soluble bioactive polyphosphazenes.
Higher biological activity
As a carrier molecule.
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31. 6. Pseudopoly[amino acids]
• Derived from simple nutrient amino acids
• No toxic degradation products.
Limitations
 antigenicity
 unfavourable material property.
 expensive.
• Slowly degrading polymer
• Long term therapy
Eg implantable multilayer contraceptive formulation.
Ttrosine-derived poly[imino carbonates]
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32. 7. Natural polymers
• Deliver drug in an area.
• Natural products of living organism .
Easily available.
Relatively in expensive.
Capable of chemical modification.
• Proteins and polysaccharides .
Collagen- solid ocular inserts.
Starch ,dextran ,cellulose ,inulin – drug carriers.[ antibiotic
enzymes]
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APPLICATIONS IN CONVENTIONAL DOSAGE FORMS
• Tablets :
- As binders
- To mask unpleasant taste
- For enteric coated tablets
• Liquids :
- Viscosity enhancers
- For controlling the flow
• Semisolids :
- In the gel preparation
- In ointments
• In transdermal Patches

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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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36. Polymers as thickening agents
Viscosity of polymer solution increases with concentration.
Viscosity of methyl cellulose has viscosity of 80 poise
Water 0.01poise
2%dissolved polymer increase viscosity up to 8000fold.
5% polymer viscosity- set into gel.
Viscosity of polymer solution is greater than free draining coils.
Thermal agitation results molecule to be entangled.
[random coils expose to large amt of solvent so Brownian motion Chain
entanglement's causes reduced viscosity
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This effect is independent of shear
Partial uncoiling, elongation and alignment of random coils results in
decreased viscosity.
Dependent of shear.
 At low shear rate.
• Chain random coil.
• Trap large amount of solvents.
• Remain entangled.
• Large flow units and high apparent viscosity.
At high shear rate.
• Uncoiled and elongated.
• Trapping less solvents.
• Usually distangled.
• Small flow units and less apparent viscosity

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SOLVENT SELECTION IN POLYMERS
• Primary functions of a solvent system is to dissolve or disperse the
polymers and other additives .
Important considerations for ideal solvent system
Should either dissolve or disperse polymer system.
Easily disperse other solution components .
Should be colorless, tasteless, odorless, inexpensive, non toxic,
inert, nonflammable.
Have a rapid drying rate.
Have no environmental impact.

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• Most widely used solvents either
alone or in combination are water,
ethanol, methanol, isopropanol,
chloroform , acetone, methylethyl
ketone, methylene chloride.

40. VISCOSITY
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Molecular weight of polymer
• Mark-Houwink equation gives a relationship between intrinsic
viscosity, [η] and molecular weight, M of a polymer solution,
expressed as:
• [η] = KMa
• where the constants, a and K, depend on the particular polymer-
solvent system.
• A value of a = 0.5 is indicative of 'theta solvent'. A value of a = 0.8 is
typical for 'good solvents'. For most flexible polymers, 0.5 ≤ a ≤ 0.8.

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Depending on the experimental techniques used, polymers may
have four different kinds of average molecular weights
1. Weight average molecular weight, Mw (light scattering)
2. Number average molecular weight, Mn (colligative
properties)
3. Z-average molecular weight, Mz (centrifugation data)
4. viscosity average molecular weight, Mv (viscometric behavior)
and the relative order of their values are:
Mz > Mw > Mv > Mn
Molecular weights based on viscosity measurements are less
precise, as it depends on the solvent used, but is less expensive
and easy to perform.

43. FABRICATION TECHNOLOGIES
Conversion of monomers or bulk polymer into the desired form.
 Methods of polymer fabrication.
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• 1. MOLDING
• 2. EXTRUSION
• 3. PREPARATION OF FILMS
1.MOLDING
 compression molding,
injection molding,
transfer molding

44. MOLDING
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• Polymer is forced to flow into a closed container having the
desired shape by the application of heat and pressure.
• The closed container is used as the mold.
• VARIOUS MOLDING PROCEDURES
• Compression molding
• Injection molding
• Transfer molding

45. Compression molding
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• Polymer is placed in the lower half of
the heated mold ,
• Mold is closed air and excess polymer
are forced out .
• Fixed pressure is applied for the
selecting time.
• The mold is cooled and the object is
removed with thermoset material .

46. Injection molding
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• Polymer is first preheated and
then forced into a cold mold
cavity by means of a hydraulic
plunger.
• The mold becomes cold.
• This is a high speed method
not require a time consuming
cooling step.
• This methodology needed an
extremely high degree of
sophistication.

47. Transfer molding
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• As the polymer is a good insulator
uniform heat transfer through out
the bulk of a sizable molded
object is difficult.
• May result in uneven setting of
thermosetting material .
• For the reason transfer molding a
combination of compression
molding and injection molding
are developed.

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• Heating the polymer in a semisolid cavity until it becomes
semisolid and forcing by means of a ram through an orfice
into the mold cavity.
• Because the entire mold is heated , thermoplastic material
cannot be removed until the mold has cooled.

49. Extrusion
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• Polymer is propelled continuously along a screw through a region of
high temp and pressure.
• It is melted and comparted and finally forced through a die to give
the final object.
• Procedure is useful for preparing rods , tubes , channels and sheets.

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PREPARATION OF FILMS
METHODS INCLUDES,
• MELT FABRICATION OR CALENDERING
• SOLUTION CASTING
• POLYMERISATION IN SITU

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MELT FABRICATION OR CALENDERING
• Films can be made through a suitably shaped disc or extrusion.
• By first extruding the `tube and then expanding the hot tube by
compressed gas into a tube of thin films.
• As in calendaring polymer is squeezed into a thin film between healed
rollers
• Films can also be produced by melt pressing where the polymer is placed
between two melted plates and the plates then placed between two heated
plates.

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SOLUTION CASTING

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•Polymer is dissolved in a suitable solvent to form a
viscous solution .
•The solution is then spread on a flat non adhesive
surface.
•Solvent is slowly evaporates .
•The resultant polymer is peeled from the surface .

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POLYMER IN -SITU
•polymerization inside a suitable
mold.
•useful for the preparation of rigid
polymers
•particularly sheets of cross linked
polymers.

55. BIBLIOGRAPHY
• file:///D:/polymerization/polymers%20with%20biodegradable.htm
• file:///D:/polymerization/Polymerization.htm
• Vishakha K et AL, Natural polymer- a comprehensive review.
International journal of research in pharmaceutical and biomedical
sciences.Dec-2012;3(4):1597-1599.
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• The Theory And Practice Of Industrial Pharmacy, Lachman /Lieberman;
Fourth Edition, Pg: No- 365-376
• Controlled Drug Delivery, Concepts And Advances; Suresh P. Vyas,pg No-
98-107
• Controlled And Novel drug Delivery, N.K.Jain ; Pg No- 365,27,31,67

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