Unit 3.1_WW.ppt POLYMERIC IMPLANT MATERIALS

POLYMERIC IMPLANT MATERIALS
SUBJECT: BIOMATERIALS

1. UBM2404 - BIOMATERIALS

2. POLYMERIC IMPLANT MATERIALS
•Polymerization
•factors influencing the properties of polymers

3. Session Objective
The objective of this session is to enable the student to
•Learn about Polymerization & the factors influencing the properties of polymers

4. Monomer
•A monomer is a molecule that binds chemically to other molecules to form a
polymer.
•The term "monomeric protein" is used to describe one of the proteins making up a
multiprotein complex.
•The most common natural monomer is glucose, which is linked by glycosidic
bonds into polymers such as cellulose, starch, and glycogen.
•The term monomer refers to the organic molecules which form synthetic
polymers.
•For example, vinyl chloride, is used to produce the polymer polyvinyl chloride
(PVC).
•The process by which monomers combine end to end to form a polymer is called
polymerization.
•Molecules made of a small number of monomer units, up to a few dozen, are
called oligomers.

6. Quaternary Structure
•A quaternary structure is the number and arrangement of multiple
protein subunits in a multi-subunit complex.
•Proteins are assemblies of multiple polypeptide chains.
•Examples of proteins with quaternary structure include hemoglobin, DNA
polymerase etc.

7. Contd.
•The number of subunits in an oligomeric complex is described using
names that end in -mer (Greek for "part, subunit").
•1 = monomer/subunit
•2 = dimer
•3 = trimer
•4 = tetramer
•5 = pentamer and so on.
•A dimer is a macromolecular complex formed by two, non-covalently
bound, macromolecules such as proteins or nucleic acids.
•It is a quaternary structure of a protein.
•A trimer is a macromolecular complex formed by three, non-covalently
bound, macromolecules like proteins or nucleic acids.

8. Large molecule composed of repeated subunits
(monomers)
Polymer
• Monomer – A substance composed of monomer
molecules
• Monomer molecule – A molecule which can
undergo polymerization to form structure of a
macro molecules
• Monomer combine to form dimers, trimers,
tetramers, pentamers and so on..
• Oligomers – Molecules made of a small number
of monomer units, up to few dozen are called
oligomers

9. Natural monomers: Amino acids, Nucleotides,
Glucose, Isoprene

10. Polymerization
•Polymerization is a process of reacting monomer molecules together in a
chemical reaction to form polymer chains or 3D networks.
•There are many forms of polymerization and different systems exist to
categorize them.

11. An example of alkene polymerization, in which each styrene monomer's
double bond reforms as a single bond plus a bond to another styrene
monomer. The product is polystyrene.

12. Condensation Polymers
•Condensation polymers are kind of polymers formed through a condensation
reaction.
•The molecules join together—losing small molecules as by-products such as water
or methanol.
•Types of condensation polymers include polyamides, polyacetals and polyesters.
•Condensation polymerization, is a process by which two molecules join together,
resulting in loss of small molecules like water.
•The type of end product resulting from a condensation polymerization is dependent
on the number of functional end groups of the monomer which can react.

13. Contd.
•Monomers with only one reactive group terminate a growing chain, and gives end
products with a lower molecular weight.
•Linear polymers are created using monomers with two reactive end groups.
•Monomers with more than two reactive end groups give three-dimensional cross-
linked polymers.

15. Addition Polymerization
•An addition polymer is a polymer formed by an addition reaction.
•The monomers bond together via rearrangement of bonds without the loss of any
atom or molecule.
•Most of the common addition polymers are formed from unsaturated monomers
(usually having a double bond).
•This includes polyethenes, polypropylene, PVC, Teflon, polyacrylates,
polystyrene etc.
•A saturated compound is a chemical compound that has a chain of carbon
atoms linked together by single bonds.

16. •Alkanes are an example of saturated compounds.
•An unsaturated compound is a chemical compound that contains carbon-carbon
double bonds or triple bonds, such as those found in alkenes (C
nH2n) or alkynes (
C
nH2n−2
), respectively.

17. Process of reacting monomer molecules together in
a chemical reaction to form polymer chain or 3D
network
Polymerization

18. Step-Growth Polymerization
•Step-growth polymers are defined as polymers formed by the stepwise reaction
between functional groups of monomers.
•Most step-growth polymers are also classified as condensation polymers.
•However, not all step-growth polymers release condensates.
•Step-growth polymers increase in molecular weight at a very slow rate at lower
conversions and reach moderately high molecular weights only at very high
conversion (i.e., >95%).

19. Chain Growth Polymerization
•Chain-growth polymerization (or addition polymerization) involves the
linking together of molecules incorporating double or triple carbon-carbon
bonds.
•These unsaturated monomers have bonds that break and link up with other
monomers to form a repeating chain, whose backbone typically contains
only carbon atoms.
•Chain-growth polymerization is involved in the manufacture of polymers
such as polyethylene, polypropylene, and polyvinyl chloride (PVC).

20. Photopolymerization
•Photopolymerization reactions are usually chain-growth polymerizations
initiated by the absorption of visible or ultraviolet light.
•The light may be absorbed either directly by the reactant monomer (direct
photopolymerization) By a photosensitizer which absorbs the light and transfers
energy to the monomer.
•In step-growth photopolymerization, absorption of light triggers a condensation
reaction.
•Photopolymerization can be used as a photographic or printing process, because
polymerization only occurs in regions which have been exposed to light.

21. Contd.
•Unreacted monomer can be removed from unexposed regions, leaving a
polymeric image.
•Several forms of 3D printing use photopolymerization.

22. Polyamid
es
Nylon - First commercial polymer made
in 1930s

23. Drawback: Tendency for reaction to stop before the
chain grow sufficient length. This is due to
decreased mobility of chains and reactant chemical
species during polymerization
Additional polymerization can be achieved by
rearranging the bonds within each monomer. Each
monomer has to share atleast two covalent
electrons with other and should have atleast one
double bond
Initiat
or

24. Initiator: Free radicals such as Benzyl
peroxide
Initiation can be activated by heat, UV, and other
chemicals
The free radical can react with monomers and this
free radical can react with other monomers and
so on…. (Propagation)

25. • Long chain molecules formed by covalent
bonding along backbone chain
• Long chain are flexible and tangled
easily

26. Degree of Polymerization is defined as average
number of repeated units per chain.
Each chain have different number depending
condition of polymerization

30. Chemical
compositi
on
Arrangem
ent of
chains
Polymer can be
tailored to meet
the use
• Increasing the molecular
weight, the polymer
chains becomes longer
and less mobile, and a
more rigid material

33. Cross-Links
•A cross-link is a bond that links one polymer chain to another.
•They can be covalent bonds or ionic bonds.
•To promote a difference in the polymers' physical properties.
•Example: When cross links are added to long rubber molecules, the flexibility decreases, the
hardness increases and the melting point increases as well.
•Cross-links can be formed by chemical reactions that are initiated by heat, pressure, change in pH,
or radiation.
•For example, mixing of an unpolymerized or partially polymerized resin with specific chemicals
called crosslinking reagents results in a chemical reaction that forms cross-links.
•The chemical process of vulcanization is a type of cross-linking that changes rubber to the hard,
durable material associated with car and bike tires.

34. • Size : Increasing the size of side chain
groups in linear polymers such as PE
decreases the melting temperature due
to decreased crystallinity.
•Lowers the melting temperature due to
the interference of cross-linking which
causes decreased mobility of the chains ,
resulting in retardation of the
crystallization rate.
• Large degree of cross linking can
prevent crystallization completely.
Example: When a cross-linking density
increases for Rubber, the material
becomes harder and Tg also increases.

35. Session Outcome
The student can be able to
•Explain the Polymerization & the factors influencing the properties of polymers.

36. Reference
1. Sujata V. Bhatt, Biomaterials, 2ndEdition, Narosa Publishing House, 2005.
2. Sreeram Ramakrishna, Murugan Ramalingam, T. S. Sampath Kumar, and
Winston O. Soboyejo, Biomaterials: A Nano Approach, CRC Press, 2010.
3. Park J.B, Biomaterials Science and Engineering, Plenum Press, 1984.