Polymer chemistry

POLYMER CHEMISTRY
Dr. P.U. Singare
Department of Chemistry,
N.M. Institute of Science, Bhavan’s College,
Andheri (West), Mumbai 400 058

Introduction
• The ability of carbon to form successive carbon-carbon bonds is called Catenation.
• This property of carbon is used to prepare giant macromolecules known as Polymers
(Poly = many & mers = parts or units).
• Polymers may be defined as high molecular weight compound formed by the
combination of a large number of one or more types of small molecules of low
molecular weight.
• This small molecules which are linked together by covalent bonds in a polymer are
called Monomers.
• Thus monomers act as a starting materials for the synthesis of polymers.

Classification of Polymers
• Polymers are broadly classified in to Two types
 Natural Polymers
 Synthetic Polymers
• Cellulose, starch, gum, rubber & proteins are natural polymers.
• Synthetic polymers are sub classified in to two sub categories
– Organic & Inorganic Polymers.
• Organic polymers consists of main chain made up of carbon atoms to which other
elements like hydrogen, oxygen, nitrogen etc are attached. eg. Polystyrene,
polyethylene etc.
• Inorganic polymers do not have main chain made up of carbon atoms eg- Glass-
which consists of metallic silicates.

Classification of Polymers
Natural Polymers Synthetic Polymers
Organic Polymers Inorganic Polymers
Depending upon the
monomers present
Depending upon the
method of preparation
Depending upon the
physical properties
Depending upon
the structure
1. Homo polymer
2. Copolymer
1. Addition polymer
2. Condensation
polymers
1. Thermoplastics
2. Thermosetting
3. Elastomers
4. Plastic, fibers, liquid resins
1. Linear polymers
2. Branched polymers
3. Crosslinked
polymers
4. Cyclic polymers

Classification of Organic Polymers based on Monomers Present
• Since monomers act as a starting materials for the synthesis of polymers, based on the monomers
present the polymers are classified as
1. Homopolymers: in which the polymers are synthesized using same type of monomer
eg. Polyethylene which is obtained by combination of single monomer which is
ethylene.
n(CH2=CH2) --(CH2-CH2)n--
(ethylene) (polyethylene)
2. Copolymers: in which the polymers are synthesized using more than one type of
monomers. eg. Nylon 6,6 which is synthesized by reaction of two different type of monomers
namely hexamethylene diamine and adipic acid.
H2N-(CH2)6-NH2 + HOOC-(CH2)4-COOH --[HN-(CH2)6-NH-CO-(CH2)4-CO)]n—
(hexamethylene diamine) (adipic acid) (Nylon 6,6 )
catalyst
high temperature /
high pressure and light
-H2O

About Homopolymers & co-polymers
https://www.youtube.com/watch?v=eyYf4MLovc0
https://www.youtube.com/watch?v=28qrk9RY-es

Classification of Organic Polymers based on methods of preparation
• Based on the methods of preparation, organic polymers are subclassified as
1. Addition polymers: are the polymers which are obtained by multiple addition of an olefinic monomers
without elimination of any simple molecules.
eg. Polyethylene which is obtained by combination of ethylene monomer without elimination of any
simple molecule.
Similarly styrene butadiene rubber is obtained by addition of styrene and butadiene without
elimination of any simple molecule.
n + n(CH2=CH-CH=CH2)
n
(Styrene) (Butadiene) (styrene butadiene rubber)
catalyst
high temperature /
HC=CH2
HC-CH2-CH2-CH=CH-CH2-----HC-CH2-CH2-CH=CH-CH2- ---HC-CH2-CH2-CH=CH-CH2-----

Classification based on methods of preparation (Continued---)
2. Condensation polymers: sometimes the monomers may react with elimination of simple
molecule like water, ammonia etc to give polymers. Such polymers are called condensation
polymers. . eg. Nylon 6,6 which is synthesized by reaction of monomers namely
hexamethylene diamine and adipic acid with elimination of water molecule.
H2N-(CH2)6-NH2 + HOOC-(CH2)4-COOH --[HN-(CH2)6-NH-CO-(CH2)4-CO)--]n—
(hexamethylene diamine) (adipic acid) (Nylon 6,6 )
-H2O

About Addition and Condensation polymers
https://www.youtube.com/watch?v=QBuSFPOtcJ4
https://www.youtube.com/watch?v=GhvevdJU_DM

Classification of Organic Polymers based on the Physical Properties
• Based on their physical properties, organic polymers are subclassified as
1. Thermoplastic resins:
 are linear or branched polymers
 soluble in many organic solvents
 soften on heating & solidify on cooling. The change is reversible i.e. they become soft again on
heating & can be reshaped.
 Example: polyethene, nylon etc.
2. Thermosetting resins:
 are three dimensional polymers.
 insoluble in all organic solvents
 soften on heating and solidify immediately. The change is irreversible i.e when heated for 2nd time they
decompose instead of becoming soft.
 Example: urea formaldehyde resins, phenol formaldehyde resins

About Thermoplastic resins & Thermosetting resins
https://www.youtube.com/watch?v=vE6x9iIgST0
https://www.e-education.psu.edu/matse81/node/2209
https://www.youtube.com/watch?v=4fTtrKPySm0
https://www.youtube.com/watch?v=0lX0AKHv0A4
https://www.youtube.com/watch?v=lNS7TwWmlrg

Classification based on the Physical Properties (Continued---)
3. Plastics: The polymers which can be shaped by application of heat and pressure are
called plastics. Example: Polyvinyl chloride (PVC), polystyrene etc.
4. Elastomers:
 The polymers which when stretched gets deformed and when the stretching force is removed, it
returns to its original form are called elastomers.
 They have high degree of elasticity and can be vulcanised into rubber products having good
strength.
 Example: synthetic rubber, silicone.
5. Fibres:
 The polymer which is in the form of long filament like material is called fibre.
 It is having the length about 80-100 times its diameter.
 Example: nylon.
6. Liquid resins:
 The polymer which is used in the liquid form is called liquid resin.
 It is used as an adhesives or sealing agent.
 Example: epoxy adhesives.

Classification of Organic Polymers based on the Structure
• Based on the structure, the polymers are subclassified as
1. Linear Polymers:
 In this polymers, all the monomer units are linked together forming long chain like structure.
 They are well packed having high densities.
 They have high intermolecular force of attraction giving them high tensile strength and high melting
point.
 Example Polyvinyl chloride (PVC), polyethylene, polyester.
2. Branched polymers:
 In this polymers, there are side chains attached to the long monomeric chain.
 The irregular packing of these polymers is responsible for low density, low melting and boiling point, low
tensile strength as compared to that of linear polymers.
 Example: starch.
3. Crosslinked polymers:
 Consist of crosslinked monomer units forming three dimensional structure of polymer.
 Because of three dimensional structure, they are very hard, brittle and rigid.
 Example: phenol formaldehyde resins, Bakelite, urea formaldehyde resins.
4. Cyclic polymers:
 Also known as cyclic olefinic polymers (COC).
 Amorphous in nature.
 They are mainly used as packing materials and vials in medicine.

Polymerization
• Polymerization: is a process in which low molecular weight compounds called monomers react to form high
molecular weight compound called polymer.
• When the monomers are used in their own state without solvent, then the process is called bulk polymerization.
• When an inert solvent is used it is called solution polymerization.
• The low molecular weight monomers are the repeating units in the polymer molecule. For example in above case
ethylene molecule is used as a monomer, hence ethylene molecules are the repeating units.
• The size and molecular weight of the polymer molecule depend on the number of repeating monomer units in it.
• The value (n) represents number of repeating units in the polymer molecule which is expressed in the term of
degree of polymerization (DP).
• When the number of repeating unit (n) is in excess of 100 , the molecule is called High Polymer.
• For example, if there are 200 repeating unit in a high polymer molecule (i.e. n = 200), then degree of
polymerization (DP) is 200.
• DP is used in expressing the molecular weight (M) of a polymer as follows
molecular weight (M) of a polymer = DP x molecular weight of a monomer (repeating units)
catalyst
high temperature /

Monomer= repeating unit = ethylene
Polymer= polyethylene
Chemical type of polymer = polyethylene
n = degree of polymerization (DP) = No. of ethylene monomers present in the polymer
M.W. of ethylene = 28
Monodisperse Polymer System
• All polymer molecules will be of same
chemical type (polyethylene)
• All polymer molecules will have same
number of ethylene monomers (repeating
units) i.e. having same degree of
polymerization i.e. same value of n.
• As a result all the polymer molecules will
have same M.W.
• Since the system is having polymer
molecules all of them have same M.W., the
system is said to be Monodisperse
Polydisperse Polymer system
• All polymer molecules will be of same chemical type
(polyethylene)
• All polymer molecules will have different number of
ethylene monomers (repeating units) i.e. having
different degree of polymerization i.e. different values
of n.
• Example: --(CH2-CH2)100— M.W. = 28x100 =2800
--(CH2-CH2)150— M.W. = 28x150 = 4200
--(CH2-CH2)200— M.W. = 28x200 = 5600
--(CH2-CH2)250— M.W. = 28x250 = 7000
And so on -----
• All the above polymer molecules will have different M.W.
• All the above polymer molecules of different M.W. are
present in the same polymeric system.
• Hence the system is Polydisperse.

Polymerization (Continued----)
• During the polymerization reaction, the polymer chain will start growing but the chain will not get
terminated after growing to the same size.
• As a result each polymer molecule formed will have different number of monomer units
(repeating units).
• Thus depending upon the monomers combined together during polymerization, the molecular
weight of each polymer molecule will be different.
• Hence, a given polymer sample consists of mixture of polymer molecules of same chemical type
but different molecular weights.
• If a polymer sample contain polymer molecules all of them having same molecular weight, then
the system of polymer is called Monodisperse system.
• However, mostly polymer system consists of polymer molecules all of them having different
molecular weight, then the system of polymer is called Polydisperse system.
• For such a polydisperse system it is necessary to consider average molecular weight, which are of
2 types:
1. Number average molecular weight(𝑀n)
2. Weight average molecular weight (𝑀w)

Number average molecular weight(𝑀n)
• Consider a polymer sample consisting of ‘ i ’ number of polymer molecules.
• Let Wi be the total weight of polymer sample having ‘ i ’ number of polymer molecules.
• Let n1 number of polymer molecules have molecular weight m1, n2 number of polymer
molecules have molecular weight m2 and so on.
• Then the Number average molecular weight(𝑀n) is the ratio of sum of weight of all polymer
molecules (Wi) to the total number of all the polymer molecules(ni) present.
𝑀n =
𝑊𝑖
𝑛𝑖
But 𝑊i= 𝑚𝑖. 𝑛𝑖
Therefore
𝑀n =
𝑚𝑖
.𝑛𝑖
𝑛𝑖
=
𝑚1
𝑛1
+𝑚2
𝑛2
+−−−−−−−−−−
𝑛1
+𝑛2
+ −−−−−−−−−−
here Wi is the total weight of polymer sample having ‘ i ’ number of polymer molecules,
ni is the number of polymer molecules of molecular weight mi

Weight average molecular weight (𝑀w)
Weight average molecular weight (𝑀w) is calculated as
𝑀w =
𝑚𝑖
.𝑊𝑖
𝑊𝑖
But 𝑊i= 𝑚𝑖. 𝑛𝑖
Therefore
𝑀w =
𝑚𝑖
.𝑚𝑖.𝑛𝑖
𝑚𝑖
.𝑛𝑖
=
𝑚𝑖
2
. 𝑛𝑖
𝑚𝑖
.𝑛𝑖
=
𝑚1
2
𝑛1
+𝑚2
2
𝑛2
+−−−−−−−−−−
𝑚1
𝑛1
+𝑚2
𝑛2
+ −−−−−−−−−−

Polydispersity and Polydispersity index
• The ratio of weight average molecular weight (𝑀w) and number average molecular weight
(𝑀n) is called polydispersity index of a polymer system.
Polydispersity index =
𝑀w
𝑀n
• The value of this Polydispersity index decide the polydispersity of a polymer system.
• Higher the ratio value greater will be the polydispersity of the polymer system.
• For polydisperse system the value of Polydispersity index is greater than unity
i.e.
𝑀w
𝑀n
> 1 hence 𝑀w > 𝑀n
• For monodisperse system the value of Polydispersity index is equal to unity
i.e.
𝑀w
𝑀n
= 1 hence 𝑀w = 𝑀n

Important formulas
Number average molecular weight(𝑀n) =
𝑊𝑖
𝑛𝑖
𝑊i= 𝑚𝑖. 𝑛𝑖
Number average molecular weight (𝑀n) =
𝑚𝑖
.𝑛𝑖
𝑛𝑖
=
𝑚1
𝑛1
+𝑚2
𝑛2
+−−−−−−−−−−
𝑛1
+𝑛2
+ −−−−−−−−−−
Weight average molecular weight (𝑀w) =
𝑚𝑖
.𝑊𝑖
𝑊𝑖
𝑀w =
𝑚𝑖
2
. 𝑛𝑖
𝑚𝑖
.𝑛𝑖
=
𝑚1
2
𝑛1
+𝑚2
2
𝑛2
+−−−−−−−−−−
𝑚1
𝑛1
+𝑚2
𝑛2
+ −−−−−−−−−−
𝑀w
𝑀n
For polydisperse system
𝑀w
𝑀n
> 1 i.e. 𝑀w > 𝑀n
For monodisperse system
𝑀w
𝑀n
= 1 i.e. 𝑀w = 𝑀n

Problem 1: A sample of polymer contains polymer chains of two distinct molecular weights 2x103 & 5x103 in the
ratio 5:2. Calculate weight average molecular weight and number average molecular weight. Calculate
polydispersity index and comment on the polydispersity of system.
Solution: Let us consider two polymer molecules A & B
For molecule A, let the molecular weight be mA = 2x103 and number of molecules be nA = 5
For molecule B, let the molecular weight be mB = 5x103 and number of molecules be nB = 2
𝑚𝐴
𝑛𝐴
+𝑚𝐵𝑛𝐵
𝑛𝐴
+𝑛𝐵
𝑀n =
2x103x5+5x103x2
5+2
=
10x103+10x103
5+2
=
20x103
7
𝑀n = 2.857 x103 = 2857
𝑚𝐴
2
𝑛𝐴
+𝑚𝐵2
𝑛𝐵
𝑚𝐴
𝑛𝐴
+𝑚𝐵𝑛𝐵
𝑀w =
2x103 2
5+(5x103)2
2
2x103x5+5x103x2
=
20000000+50000000
10000+10000
=
20000000+50000000
10000+10000
𝑀w =
70000000
20000
=
7000
2
= 3500
𝑀w
𝑀n
=
3500
2857
= 1.23
Since Polydispersity index > 1 i. e. 𝑀w > 𝑀n the system is polydisperse

Problem 2: Determine the number average and weight average molecular weight of a sample containing 50 g pf
polymer A having M.W. 14,000 and 130 g of Polymer B having M.W.17,000
Given: mass of polymer A (WA) = 50 g; M.W. of polymer A (mA) = 14,000
mass of polymer B (WB) = 130 g; M.W. of polymer B (mB) = 17,000
Solution: 𝑊A= 𝑚𝐴. 𝑛𝐴 hence 𝑛𝐴 =
𝑊A
𝑚𝐴
=
50
14,000
Similarly 𝑊B= 𝑚𝐵. 𝑛𝐵 hence 𝑛𝐵 =
𝑊B
𝑚𝐵
=
130
17,000
𝑚𝐴
𝑛𝐴
+𝑚𝐵𝑛𝐵
𝑛𝐴
+𝑛𝐵
𝑀n =
14,000x
50
14000
+17000x
130
17000
50
14000
+
130
17000
=
50+130
0.00357+0.00765
=
180
0.01122
𝑀n = 16042.8 ≈ 16043
𝑚𝐴
2
𝑛𝐴
+𝑚𝐵2
𝑛𝐵
𝑚𝐴
𝑛𝐴
+𝑚𝐵𝑛𝐵
𝑀w =
14000 2 50
14,000
+(17,000)2 130
17,000
14000 50
14,000
+(17,000)
130
17,000
=
14000 50+(17,000)
130
50+
130
𝑀w =
70,0000+221,0000
180
𝑀w = 16166.66 ≈ 16,167
Since 𝑀w > 𝑀n the system is polydisperse

Problem 3: A solution of protein contain equimolar mixture of protein A (m =13700) and protein B (m =15500).
Calculate weight average molecular weight and number average molecular weight.
Given: mA= 13700 & mB = 15500
Since a solution of protein contain equimolar mixture of protein A and protein B, nA = nB = n
𝑚𝐴
𝑛𝐴
+𝑚𝐵𝑛𝐵
𝑛𝐴
+𝑛𝐵
=
𝑚𝐴
𝑛+𝑚𝐵𝑛
𝑛+𝑛
=
(𝑚𝐴
+𝑚𝐵)𝑛
2𝑛
=
(𝑚𝐴+𝑚𝐵)
2
𝑀n =
(13700+15500)
2
= 14600
𝑚𝐴
2
𝑛+𝑚𝐵2
𝑛
𝑚𝐴
𝑛+𝑚𝐵𝑛
=
(𝑚𝐴
2
+𝑚𝐵2
)𝑛
(𝑚𝐴
+𝑚𝐵)𝑛
=
(𝑚𝐴2
+𝑚𝐵2
)
(𝑚𝐴+𝑚𝐵)
𝑀w =
(13700)2
+(15500)2
(13700 +15500)
=
(187690000)+(240250000)
29200
𝑀w =
427940000
29200
= 14655.48 ≈ 14655
Since 𝑀w > 𝑀n the system is polydisperse

Problem 4: Equal number of molecules with m1 = 1000 and m2 =10,000 are mixed. Calculate weight
average molecular weight and number average molecular weight.
Solution: Since equal number of molecules are present means n1 =n2 = n
Answer:
Number average molecular weight (𝑀n) = 5500
Weight average molecular weight (𝑀w) = 9181.8 ≈ 9182

Problem 5: Equal weight of polymer molecules with mA = 1000 and mB = 10,000 are mixed together.
Calculate weight average molecular weight and number average molecular weight. Calculate
polydispersity index and comment on the polydispersity of system.
Solution: Since equal weight of polymer molecules are mixed together WA = WB = 20,000 (say)
𝑊A= 𝑚𝐴. 𝑛𝐴 hence 𝑛𝐴 =
𝑊A
𝑚𝐴
=
20,000
1000
= 20
Similarly 𝑊B= 𝑚𝐵. 𝑛𝐵 hence 𝑛𝐵 =
𝑊B
𝑚𝐵
=
20,000
10,000
= 2
𝑚𝐴
𝑛𝐴
+𝑚𝐵𝑛𝐵
𝑛𝐴
+𝑛𝐵
𝑀n =
1000x 20+10,000x 2
20+2
=
20,000+20,000
22
=
40,000
22
𝑀n = 1818.2 ≈ 1818
𝑚𝐴
2
𝑛𝐴
+𝑚𝐵2
𝑛𝐵
𝑚𝐴
𝑛𝐴
+𝑚𝐵𝑛𝐵
𝑀w =
1000 2
20+(10,000)2
2
1000x 20+10,000x 2
=
20,000000+200000000
20,000+20,000
= 5500
𝑀w
𝑀n
=
5500
1818
= 3.03
Since Polydispersity index > 1 i. e. 𝑀w > 𝑀n the system is polydisperse

Viscosity method to determine Viscosity Average Molecular weight
• The property by virtue of which a liquid resists the relative motion of one layer of liquid
over other layer is called Viscosity.
• The viscosity is represented by a symbol (ƞ) pronounced as “eta”
• Generally the Viscosity of unknown polymer sample is found out by using Ostwald’s
Viscometer.
• In this method the viscosity of polymer sample is determined by comparing its viscosity
with a standard solvent like water whose viscosity is known.
• The apparatus consists of a U-Shaped glass tube with two arms each
having a bulb (A) and bulb (B) of different capacities.
• The higher bulb (B) has a fine capillary on its lower side.
• There are two markings above and below the bulb (B): Upper mark C &
Lower mark (D).
• The liquid polymer sample and solvent (Water) is introduced in Bulb (A)
through the Arm 1.
• A rubber tubing which is attached to the arm 2 is used to suck the
sample or solvent from bulb (A) in to the bulb (B) above the Upper mark
C.

Viscosity method (Continued----)
• Initially a suitable solvent like water whose viscosity is known
is introduced in bulb A through the arm 1.
• By means of a rubber tubing attached to the Arm 2 the
solvent water is sucked in bulb B above the Upper mark C.
• The solvent is now allowed to flow down freely.
• As the solvent level reach the Upper mark C, the stopwatch is
started.
• As the solvent level reach the lower mark D, the stop watch is
stopped.
• The efflux time (in seconds) for the solvent to flow from
Upper mark C to lower mark D is recorded.
• The solvent is now removed from the viscometer and the
viscometer is cleaned thoroughly.
• Now the above procedure is repeated for the 5 different
polymer solutions of increasing concentrations (like 0.1%,
0.25%, 0.50%, 0.75% & 1.0%) and the efflux time for each
polymer solution is measured as explained above.

• Knowing the efflux time for a solvent (water) and the efflux time for different polymer solutions of 0.1%,
0.25%, 0.50%, 0.75% & 1.0% concentrations, the relative viscosity (ƞrel) for different polymer solutions is
calculated by the formula
ƞrel =
𝑒𝑓𝑓𝑙𝑢𝑥 𝑡𝑖𝑚𝑒 𝑓𝑜𝑟 𝑝𝑜𝑙𝑦𝑚𝑒𝑟 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑜𝑓 𝑎 𝑔𝑖𝑣𝑒𝑛 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛
𝑒𝑓𝑓𝑙𝑢𝑥 𝑡𝑖𝑚𝑒 𝑓𝑜𝑟 𝑡ℎ𝑒 𝑠𝑜𝑙𝑣𝑒𝑛𝑡 𝑤𝑎𝑡𝑒𝑟 (𝑡𝑠)
------ (1)
• From the calculated values of relative viscosity (ƞrel), specific viscosity (ƞsp) is calculated for each polymer
solution using equation
ƞsp = ƞrel – 1 -------- (2)
% Concentration of Polymer solution
(C)
Efflux time
(s)
Ƞrel Ƞsp = ƞrel -1 Ƞsp/C
0 (blank solution having only water) ts ---
0.10 t1 t1/ts
0.25 t2 t2/ts
0.50 t3 t3/ts
0.75 t4 t4/ts
1.00 t5 t5/ts

• A graph of Ƞsp/C against concentration (%) is
plotted which is a straight line.
• The straight line is extrapolated to meet Y-axis.
• The intercept on Y- axis will give the value of
intrinsic viscosity (ƞInt).
• The intrinsic viscosity (ƞInt) is related to
viscosity average molecular weight by
Mark Houwink equation
ƞInt = K.Mv
α ------------ (3)
Here ‘K’ and α are the constants for a given
polymer solution.
• Simplifying the eq(3) we get
Mv =
α
ƞInt/K -------------- (4)
• Since the value of K & α are the constants for a given
polymer solution, knowing the ƞInt value from graph,
the viscosity average molecular weight (Mv) can be
calculated using eq (4).
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 0.25 0.5 0.75 1
Ƞsp/C
Concentration (%)

• The ratio Ƞsp/C indicate relative increase in specific viscosity per unit concentration of
polymer.
• It is also known as reduced viscosity.
• It depends upon the concentration of a polymer solution.
• Therefore the plot Ƞsp/C against concentration is extrapolated to zero concentration.
• This extrapolated value is known as intrinsic viscosity (ƞInt) which is also called viscosity
number or Staudinger index.
ƞInt = C0
𝑙𝑖𝑚 Ƞsp
𝐶

Important formulas
ƞInt = K.Mv
α
Mv =
α
ƞInt/K
ƞsp = ƞrel – 1
ƞInt = C0
𝑙𝑖𝑚 Ƞsp
𝐶
ƞInt = C0
𝑙𝑖𝑚 ƞrel – 1
𝐶

Problem 6. The intrinsic viscosity of a polymer in an organic solvent was found to be 1.60 at 298K. Calculate the
viscosity average molecular weight of the polymer solution. Given: K= 5.1X104 α = 0.73
Given: ƞInt = 1.60, K= 5.1X104 , α = 0.73
To Find: Mv = ?
Formula: Mv =
α
ƞInt/K
Solution: Mv =
α
ƞInt/K
log Mv =
1
α
(log ƞInt - log K)
log Mv =
1
0.73
(log 1.60 - log 5.1X104)
log Mv = 1.3699 (log 1.60 - log 0.00051)
log Mv = 1.3699 [0.20412- (-3.29243)]
log Mv = 1.3699 [0.20412 + 3.29243]
log Mv = 1.3699 [3.49655]
log Mv = 4.78992
Mv = a.log(4.78992)
Mv = 61,648 g/mol

Problem 7. For a polymer solution in CHCl3 of concentration 3.0 g/dl, the specific viscosity was
found to be 0.12. Calculate the molecular weight of a polymer. Given: K = 3.2X10-6 α = 0.85
Given: C = 3.0 g/dL, ƞsp = 0.12 , K = 3.2X10-6 α = 0.85
To find: Mv = ?
Formula: ƞInt = C0
𝑙𝑖𝑚 Ƞsp
𝐶
ƞInt = K.Mv
α
Solution: ƞInt = C0
𝑙𝑖𝑚 Ƞsp
𝐶
ƞInt = C0
𝑙𝑖𝑚 0.12
3
= 0.04
ƞInt = K.Mv
α
0.04 = (3.2X10-6).Mv
0.85
Mv
0.85 =
0.04
3.2X10−6
= 12,500
Mv
0.85 = 12,500
0.85logMv = log (12,500)
0.85 log Mv =4.0969
log Mv = 4.8199
Mv = a.log (4.8199)
Mv = 66,054 g/mol

Problem 8. The intrinsic viscosity of a polymer is 217 cm3/g. Calculate the approximate
concentration of a polymer in water having relative viscosity of 1.5.
Given: ƞInt = 217 cm3/g ƞrel = 1.5
To Find: C = ?
𝑙𝑖𝑚 Ƞsp
𝐶
ƞsp = ƞrel – 1
Solution: ƞsp = ƞrel – 1
ƞsp = 1.5– 1
ƞsp = 0.5
ƞInt = C0
𝑙𝑖𝑚 Ƞsp
𝐶
217 =
0.5
𝐶
C =
0.5
217
C = 0.0023 = 2.3x10-3 g/cm3

Problem 9. For a polymer solution of concentration 3.5x10-4 g/cm3 , if the intrinsic viscosity of a
polymer is 350 cm3/g. Calculate the specific viscosity and relative viscosity of a polymer solution.
Given: ƞInt = 350 cm3/g C = 3.5x10-4 g/cm3
To Find: ƞsp = ?
ƞrel = ?
𝑙𝑖𝑚 Ƞsp
𝐶
Solution: ƞInt = C0
𝑙𝑖𝑚 Ƞsp
𝐶
350 = C0
𝑙𝑖𝑚 Ƞsp
3.5x10−4
ƞsp = 350 x 3.5x10−4
ƞsp = 0.1225
ƞsp = ƞrel – 1
ƞrel = ƞsp +1
ƞrel = 0.1225 +1
ƞrel = 1.1225

Problem 10. Calculate the intrinsic viscosity of a polymer solution having relative viscosity 1.8 and
concentration 5.4 x10-3 g/cm3 .
Given: ƞrel = 1.8 C = 5.4x10-3 g/cm3
To Find: ƞint = ?
𝑙𝑖𝑚 Ƞsp
𝐶
ƞsp = ƞrel – 1
Solution: ƞsp = ƞrel – 1
ƞsp = 1.8– 1
ƞsp = 0.8
ƞInt = C0
𝑙𝑖𝑚 Ƞsp
𝐶
ƞInt = C0
𝑙𝑖𝑚 0.8
5.4x10−3
ƞInt = 148

Light Emitting Polymers (LEP)
• LEP’s are the polymers that emits light when voltage is applied to it.
• This property is called electroluminescence.
• They are called conducting polymers because they have metallic and semiconducting
properties.
• They are special plastic materials that convert electrical power into visible light.
• LEP’s are used to manufacture light weight, ultra thin displays for mobiles, TV screens,
computer displays.
• Examples of LEP’s are Polyphenylene Vinylene (PPV) and its derivatives like polythiophenes,
polypyridines, polyphenylenes.
• Flexible Organic Light Emitting Diodes (FOLED’s) are made by applying thin film of
semiconducting polymers on the surface of optically clear plastic films or on the surface of
reflective metal foils.
• These LED’s can be bent, rolled, and displayed in any shape.
• They are ultra light weight and thin, less fragile, more impact resistant and durable.
• They can be manufactured in mass production at low cost.

Structure and Working of LEP devices or Polymer based LED
Construction
• The structure of LEP consist of a thin film
of semiconducting p-phenylene vinylene
(PPV)polymer solution coated on
Indium-Tin oxide (ITO) coated glass.
• The polymer solution is coated on the
glass surface and is thermally heated to
high temperature which result in the
formation of dense pin hole free film on
the glass substrate.
• The thickness of polymer film is in the
order of 100 nm.
• This film of semiconducting polymer is
sandwiched between the anode and
cathode.
• In this device ITO act as a anode and Al
metal act as a cathode.
Glass
ITO Layer
Polymer film
Al electrode
excition

Structure &Working of LEP devices or Polymer based LED (Continued---)
Working
• When a voltage is applied between the
two electrodes, the positively charged
holes and negatively charged electrons
from the electrodes move into the
conducting polymer film.
• These moving holes & electrons
combine together to form hole-electron
pairs which are known as excitions.
• These excitions are in excited state.
• When they return back to the ground
state they emit energy in the form of
light.
Glass
ITO Layer
Polymer film
Al electrode
excition

Advantages
• Require only 3.3V and have lifetime of more than 30,000h.
• Greater power efficiency.
• No directional or blurring effect and hence can be viewed properly from all angle.
• Cost of manufacturing is very less because the active material is polymer.
• Fast switching speed.
• Due to high refractive index of the polymer, only a small fraction of light generated in the
polymer layer escape the polymer film. Hence they have high luminescence efficiency.
• LEP range from tiny device (dimension in mm) to high definition devices (up to 5mt in
diameter).

Applications
• The ultra thin and light weight of polymer films are used in flat panel displays in cell
phones, portable computers and TV screens.
• Transparent organic light emitting devices (OLED’s) are used in dynamic credit cards.
• Used to prepare organic solar cells.

Stabilisers & Antioxidants
• Plastic polymers and elastomers on exposure to oxidative environment will undergo ageing
and degradation which is indicated by discolouration and yellowing of polymers or loss of
gloss in case of a plastics.
• This will result in reduction of mechanical properties like flexibility, strength and stiffness of
polymers.
• During the moulding or casting of plastics, they are often heated above their melting point
temperature.
• Under this condition, there is a possibility that the plastic polymeric materials will undergo
auto oxidation by reacting with atmospheric oxygen.
• During this process, added antioxidants plays an important role by inhibiting auto oxidation
of plastic polymeric materials.
• The substances which when added to the polymers will help to improve the mechanical and
physical properties of polymers are called Stabilisers and Antioxidants.

Thermal stabilisers
• They are the salts of heavy metals, metallic salts of organic acids.
• When added to the plastic polymeric materials they protect the plastic
materials from high temperature during processing and storage of plastics.
• Barium-zinc additives are very effective heat stabilizers for PVC but are
restricted for medical applications in some countries.
• Alternatives like calcium-zinc formulations are often used to stabilize medical-
grade PVC against heat.
• Heat stabilizers trap the hydrogen chloride that is generated when PVC
decomposes at high temperatures and prevent discoloration and degradation.
• For silicon sealants and adhesives- Iron oxide and carbon black are added as a
heat stabilisers.
• They prevent discoloration and degradation of sealants and adhesive
materials.

UV-light stabilizers
• Many polymeric materials on exposure to strong UV radiations from sunlight will degrade
and become yellow in colour.
• In order to prevent the UV deterioration of polymeric materials, UV stabilizers are added.
• Addition of light stabilizers/UV absorbers can extend the life and hence, improve
the appearance of the plastic.
• Selection of a light stabilizer / UV absorber largely depends upon the substrate to be
protected, its envisioned functional life and its sensitivity to photodegradation.
• The most common UV absorbers are benzotriazoles, oxanilides,
benzophenones and organic nickel compounds.
• Zinc derivatives of mono-alkyl H-phosphonates are used as a UV stabilizers for cellulose and
polyesters.
• For polyvinyl chloride (PVC) polymeric materials, mixture of metal salts like Mg, Ca, Pb, Sn,
Zn, Ba, Cd) of different mono alkyl H-Phosphonates are added as a UV- Stabilisers.
• Such UV stabilizers in the concentration of less than 1% will help to improve UV light
transmission from the polymeric materials thereby reducing the yellowness and
deterioration of polymers.

Plastic Colorants
• There are many plastic products around us, such as plastic bottles, stationery, and food containers.
• These plastic products are not originally colored. Plastics are nearly colorless (milky-white).
• Colorants such as pigments are added to produce plastic products in various colors.
• There are roughly two methods of coloring: external coloring and internal coloring.
• External coloring is a method of coloring the surface of plastics. It applies to printing, coating, and
plating.
• Internal coloring is a method of coloring plastics by kneading colorants into them. Unlike external
coloring, materials are colored evenly up to the inside, because colorants are mixed with plastics.
• Colorants used for internal coloring are generically called Plastic Colorants.
• They are dyes and pigment compounds which are used for coloring the polymeric materials like
polycarbonates, polystyrene, and acrylic polymers.
• The colorants used for colouring the polymeric materials should be chemically stable during
processing of polymers at high temperature and fabrication process.
• Examples of plastic colourants include Oil blue A Dye, Disperse red 11 dye, diarylide pigments.
• Such colourants provide the desired colouring effect to polymeric materials and they can withstand
high temperature and heat changes.

Antistatic agents
• Development of static charges on the surface of plastic materials affect the processing of plastic
materials.
• It is a matter of great concern from hygiene and aesthetic point of view.
• In order to reduce or eliminate the effect of development of static charge in the plastic materials,
antistatic agents are added to it.
• An antistatic agent is a compound used for treatment of materials or their surfaces in order to
reduce or eliminate buildup of static electricity.
• The role of an antistatic agent is to make the surface or the material itself slightly conductive, either
by being conductive itself, or by absorbing moisture from the air.
• The molecules of an antistatic agent often have both hydrophilic and hydrophobic areas, similar to
those of a surfactant; the hydrophobic side interacts with the surface of the material, while the
hydrophilic side interacts with the air moisture and binds the water molecules.
• Such antistatic agents can be sprayed externally on the surface of plastic materials.
• Antistatic agents can be added to nonpolar solvents to increase their conductivity & to allow
electrostatic spray painting.
• Common antistatic agents are based on long-chain aliphatic amines (optionally ethoxylated)
and amides, quaternary ammonium salts, esters of phosphoric acid, polyethylene glycol esters.

Antistatic agents (Continued---)
• Alternately they can be added internally into the polymeric matrix when they migrate
to the surface of plastic materials.
• Migrating antistatic agents offer cost-effective protection for short-term applications.
• Traditional migrating antistatic agents include long-chain alkyl phenols, ethoxylated
amines, and glycerol esters, such as glycerol monostearate.

Curing agents
• The process of hardening and toughening of polymeric materials is called Curing.
• The hardness or toughness of polymeric materials can be brought about by heating,
electron beam impact or by incorporating chemical additives.
• In the curing process when the chemical additives are activated by exposure to UV
radiation, the process is called UV-Curing.
• Polyamines, polythiols, poly amido amines are some of the examples of curing agents used
for epoxy resins.

Polymer chemistry

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