Download POLYMER CHEMISTRY Lecture/Lession Plan -1

Chapter 6
POLYMER CHEMISTRY
Lecture/Lession Plan -1
POLYMER CHEMISTRY
6.1
Introduction
The Natural giant molecules DNA which contains all the genetic information from generation to
generation is a macromolecule. Similarly biomolecules like starch, cellulose, proteins, enzymes etc.
and synthetic compunds like polythene, polyvinyl chloride are also class of macromolecules. Among
these macromolecules some macromolecules have large number (Hundred to ten thousand or more)
of repeating simple monomer unit joint together through covalent bonds which is called polymer
and the process of formation of polymer from the simple starting molecules is called polymerization.
The word ”Polymer” have been taken from greek word ”Poly”, which means many and ”meros”
which means part or unit. Polymers have very high molecular weight. Polymers are macromolecules
but chlorophyll, butter, Tween 20, Tween 60, Tween 80, Sodium dodecyl sulphonates (SDS), Cetyl
trimethyl ammonium bromide(CTAB) are macromolecule due to their giant structure but having
no repeating unit of monomer that is why they are not polymer.
6.2
Monomer
The smallest unit or part which combine togetherrepeatedly to form polymers is called monomers.
Polythene is a polymer which is formed by the combination (addition) of ETHYLENE monomer
unit.
nC2 H4 → (C2 H4 )n .
6.3
Degree of polymerization
The number of monomer unit present in a polymer is called degree of polymerization.
Synthetic polymer are mainly prepared from organic compounds having long chain molecules but
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there are so many polymer which are mainly prepared from inorganic compounds like metaphosphoric acid (HPO3 )n , silicates (SiO2 )n , asbestos fiber.
6.4
Classification of polymers
Polymer can be classifieon different basis.
1. Classification On the basis of origin
2. Classification On the basis of used monomer
3. Classification On the basis of copolymer structure
4. Classification on the basis of chain growth
5. Classification on the basis of mode of polymeric growth
6. Classification on the basis of tactility
7. Classification on the basis of molecular force
6.4.1
Classification on the basis of origin
On the basis of origin polymer can be divided into two categories:
a) Natural polymer
b) Synthetic polymer
c) Semi-synthetic polymer
Natural polymer: Complex compound which obtained from natural resources having high molecular mass and weak molecular forces are called natural polymer. Natural rubber, protein, starch,
cellulose, gum resin silk and wool are example of natural polymer.
Natural rubber is a sappy material obtained from latex of rubber tree (plant in the tropical zone) is
a polymer of cis poly isoprene (cis-2 − methyle − 1, 3 − butadiene) having average molecular weight
about one million.
Proteins are the large polymer of different amino acid (contain −NH2 and − COOH) having amide
linkage by the condensation (removal of one molecule of water) of one −NH2 and − COOH.
Starch and cellulose are polymers made from monosaccharide (α − D -glucose) and (β − D -glucose)
respectively.
Synthetic polymer: Depending on demand and supply there are variety of artificially synthetic
polymer which is obtained from chemical resources having high molecular mass and weak molecular
forces. Synthetic polymers can be made to achieve such properties which cannot be achieved with
natural polymer. They can withstand very high temperature and resistance to many chemicals.
Synthetic rubber (Styrenebutadiene rubber or Buna-S,nitrile rubber or Buna-N), Polyvinylchloride(PVC), Bakelite, Teflon, nylon etc. are examples of synthetic polymer.
Semi-synthetic polymer: To increase the different properties of natural polymers they are treated
by some chemical which are called semi synthetic polymer. Vulcanised rubber, nitrocellulose, cellulose acetate etc. are examples of semi-synthetic polymer.
6.4.2
Classification on the basis of used monomer
On the basis of used monomer polymer can be divided into two categories:
a) Homopolymer
b) Copolymer
6.4. CLASSIFICATION OF POLYMERS
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Homopolymer: Polymer obtained from only one type of monomer unit is called homopolymer.
Polyethylene, polyvinylchloride, polystyrene, polybutadiene, polyacrylonitrile, polypropylene etc.
are examples of homopolymer.
Homopolymer - PVC
Copolymer: Polymer obtained by the simple addition of more than one monomer unit or condensation(release of material during reaction) of more than one type of monomer unit having bi
or more functional group is called copolymer. Styrene butadiene rubber(SBR or Buna-S), Nitrile
rubber(NBR or Buna-N rubber), nylon-66 etc. are examples of copolymer.
Copolymer - Nylon6,6
polyester, Phenol formaldehyde resin, Melamine formaldehyde resin.
6.4.3
Classification on the basis of copolymer structure:
On the basis of copolymer structure polymer can be divided into two categories:
a) Block copolymer
b) Graft copolymer
a) Block copolymer: A linear chain copolymer in which one monomer unit is blocked by other
monomer unit in various manner are called block copolymer. Example: Styrenebutadiene(SBR)
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Block copolymer - SBR - Shoe sole
b) Graft copolymer: A branched chain copolymer in which one monomer unit form the main
or long backbone chain and branches attached to it are made by other monomer is called graft
copolymer. Example: High Impact Polystyrene (HIPS) consists of the polystyrene backbone with
polybutadiene chains branching from it in each direction.
Graft copolymer - SBR(CD case)
6.4. CLASSIFICATION OF POLYMERS
6.4.4
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Classification on the basis of chain Growth
On the basis of chain growth polymer can be divided into to three parts:
a) Linear chain polymer
b) Branched chain polymer
c) Cross linked polymer
Linear, branched and cross linked polymer
a)Linear chain polymer: Polymer in which single monomer (incase of homo polymer) or more
than one monomer (incase of copolymer) units are linked together to form only long chain or straight
chain linear polymer called linear chain polymer. Due to their linear structure the different polymeric
backbone chain these chains are well fitted to each other, having high density and high melting point.
Example: High density polyethylene(HDPE) Polyvinylchloride(PVC) Polystyrene(PS) Polybutadiene etc.(homopolymer); Nylon-66 Styrene butadiene polyester(copolymer)etc.
b) Branched chain polymer: Polymer in which single monomer unit (incase of homo polymer)
or more than one monomer (incase of copolymer) units are linked together to form long chain with
long or short branch throughout the long backbone chain is called branched chain polymer. Due
to presence of branch throughout the polymeric backbone chain these chains are not well fitted to
each other and hence they are low density polymer with high melting point. Example: Low density
polyethylene(LDPE) Glycogen etc. (homopolymer:)
c) Cross linked polymer: Polymer in which normally more than one monomer (incase of copolymer) units are linked together to form long chain and different long backbone chains are randomly
cross linked resulting in the three dimensional network structure called branched chain polymer. Due
to presence of three dimensional cross link throughout the different polymeric backbone chain with
a giant molecular structure and make the structure rigid hard and brittle. Example: Homo polymer:
Vulcanized rubber Bakelite (PF) resin Urea formaldehyde(UF) resin Melamine formaldehyde(MF)
resin etc.
6.4.5
Classification on the basis of mode of polymeric growth
a) Addition polymerization
b) Condensation polymerization
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a). Addition polymerization :
Addition polymerization
During the process of polymeric chain growth if there is only addition of monomers with out any
loss of small molecules like H2 O, NH3 , alcohol etc. and the polymer is an exact multiple of used
monomer unit then the polymerization process is called addition polymerization. Example of addition polymers are PE PVC, PP etc.
b). Condensation polymerization:
Condensation polymerization
During the process of polymeric chain growth if chemical reaction takes place between different
functional group of single monomer or different monomers with the loss of compound like HCl,
H2 O or other compounds and the polymer is not an exact multiple of used monomer unit then the
polymerization process is called condensation polymer polymerization. Example of condensation
polymers are PF, UF, MF, Nylon, PET etc.
Different between addition and condensation polymerization:
6.4. CLASSIFICATION OF POLYMERS
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Addition polymerization
A) This type of polymerization
occur by the addition of
single monomer unit.
B) Generally the used monomer have
no functional group.
C) Empirical formula of the polymer
is same as molecular formula and
molecular formula is an integral
multiple of empirical formula
D) Polymerization takes place without
loss of any compound.
E) Polymerization takes places by
linear or branch polymerization.
J) Example of these these polymers
are polymers are PVC,PE,
PP
Condensation polymerization
A) This type of polymerization
occur by the condensation of
occur by single monomer unit.
B) Generally the used monomer have
Two or more functional group.
C) Empirical formula of the polymer
is not same as molecular formula
and molecular formula is not an
integral multiple of empirical formula
D) Polymerization takes place with
loss of compound.
E) Polymerization takes places by
cross linked polymerization polymer
J) Example of these these
are Nylon6,6, PF , MF, UF resin,
Epoxy rein,Polyester resin etc.
Preparation of some important addition polymer:
1) Nylon6,6
2) Nylon 6
3) polyester or poly ethylene teriphthalate
1) Nylon-6,6:
Nilon-6,6
Nylon-6,6 is a polymer having poly amide group (-CONH-) in a long back bone chain. It is a thin
and trade type polymer and capable of forming fiber. Nylon-6,6 is prepared from equimolar ratio of
hexamethylene diamine and adipic acid at a temperature 900 C. The number 6,6 indicate the carbon
atoms. It is an example of copolymer ans linear polymer same time. The preparation method of
nylon-6,6 is condensation polymerization process.
2) Nylon-6:
Nilon-6 from caprolactum
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Nilon-6 from caproic acid
Nylon-6 is a polymer having poly amide group (-CONH-) in a long back bone chain. It is a thin
and trade type polymer and capable of forming fiber. Nylon-6 is prepared from ε-amino caproic
acid by self condensation at a temperature 900 C. The number 6 indicate the carbon atoms present
in monomer unit. Unlike nylon-6,6, nynol-6 is a homopolymer.
3) polyester or poly ethylene terephthalate(PET): Polyester is a polymer having poly ester
group(-COOC-)in long back bone chain. It is a thin and trade type polymer and capable of forming
fiber. The important polyester is poly ethylene terephthalate (PET). It is prepared from equimolar
ratio of ethylene glycol and terephthalic acid at a temperature 140 − 1900 C.
PET
Characteristics of polyester or poly ethylene terephthalate (PET):
a) Polyester is colour less odour less polymer soluble in ester amyl acetate
b) It is a condensation polymer .
c) Resistance to insect, heat and moisture also.
d) Chemically inert, nonpolar, moisture resistance and highly resistance to any acid base.
e) Produce fine highly tough wrinkle free but flexible fiber.
f) Resistance to any acid base except HNO3 .
Uses of polyester
a) As produce high quality fiber like dacron, terylene they normally used for the preparation of
clothes.
b) These are used for the preparation of high quality magnetic recording tape.
c) Fir thin and thread type having high tensile strength they are used as curtain, fishing line.