Molecular Weights of Polymers | Chemistry Optional Notes for UPSC PDF Download

 Page 1


Molecular Weight of Polymers
Page 2


Molecular Weight of Polymers
Introduction 
?Polymers are long chain molecules produced by linking small repeat
units (monomers) together
?Polymers exhibit very different physical properties compared to the
monomers, dependent on the length of the polymer chains
?The presence of small amounts of very long or very short chains can
have drastic effects on properties of the material
Page 3


Molecular Weight of Polymers
Introduction 
?Polymers are long chain molecules produced by linking small repeat
units (monomers) together
?Polymers exhibit very different physical properties compared to the
monomers, dependent on the length of the polymer chains
?The presence of small amounts of very long or very short chains can
have drastic effects on properties of the material
Molecular Weight 
?Repetitive units make up a polymer.
?These repetitive units were originally the monomer molecules.
?When polymer chains form their lengths their weights differ.
?It is important to be able to characterize the polymer structure.
?Determining the weight-average molecular weight or the number-
average molecular weight is a part of any polymer characterization
“Molecu lar weight of a polymer is defined as sum of the
atomic weight of each of the atoms in the molecules,
which is present in the polymer”
Page 4


Molecular Weight of Polymers
Introduction 
?Polymers are long chain molecules produced by linking small repeat
units (monomers) together
?Polymers exhibit very different physical properties compared to the
monomers, dependent on the length of the polymer chains
?The presence of small amounts of very long or very short chains can
have drastic effects on properties of the material
Molecular Weight 
?Repetitive units make up a polymer.
?These repetitive units were originally the monomer molecules.
?When polymer chains form their lengths their weights differ.
?It is important to be able to characterize the polymer structure.
?Determining the weight-average molecular weight or the number-
average molecular weight is a part of any polymer characterization
“Molecu lar weight of a polymer is defined as sum of the
atomic weight of each of the atoms in the molecules,
which is present in the polymer”
Let's think about a small molecule, say, hexane. Hexane has a molecular
weight of 86. Every hexane molecule has a molecular weight of 86.
C C C
C
C
C
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Hexane has one molecular weight, 86
Page 5


Molecular Weight of Polymers
Introduction 
?Polymers are long chain molecules produced by linking small repeat
units (monomers) together
?Polymers exhibit very different physical properties compared to the
monomers, dependent on the length of the polymer chains
?The presence of small amounts of very long or very short chains can
have drastic effects on properties of the material
Molecular Weight 
?Repetitive units make up a polymer.
?These repetitive units were originally the monomer molecules.
?When polymer chains form their lengths their weights differ.
?It is important to be able to characterize the polymer structure.
?Determining the weight-average molecular weight or the number-
average molecular weight is a part of any polymer characterization
“Molecu lar weight of a polymer is defined as sum of the
atomic weight of each of the atoms in the molecules,
which is present in the polymer”
Let's think about a small molecule, say, hexane. Hexane has a molecular
weight of 86. Every hexane molecule has a molecular weight of 86.
C C C
C
C
C
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Hexane has one molecular weight, 86
C C C
C
C
C
H
H
H
H
H
H
H
H
H
H
H
H
H
H
C
H
H
Lengthening the carbon chain by one carbon turns hexane into a
completely different compound, Heptane, molecular weight = 100
Now if we add another carbon to our chain, and the appropriate amount
of hydrogen atoms, we've increased our molecular weight to 100.