Chemistry Reference
In-Depth Information
1.1
Introduction
In today's world, polymers constitute an important class of materials and are the
appropriate substitutes for conventional materials. These materials have been
proved to be of industrial importance in diversified fields [
1
-
4
]. However, most
of the polymers are not able to perform under high temperature and pressure
conditions because of which the concept of speciality polymers emerged. Different
modification techniques have been developed to enhance the properties of poly-
meric materials under required conditions [
5
-
8
]. Surface morphology of polymers
is of great interest, and commercially important products can be developed through
the introduction of reactive sites. Such reaction sites are used for the incorporation
of properties like hydrophilicity, hydrophobicity and resistance towards acid-base
attack along with higher thermal stability [
9
,
10
].
Graft copolymerisation provides a tool in the hands of researchers to incorporate
targeted properties in backbones for specialised applications without affecting their
biodegradability. It is a technique to hybridise synthetic and natural polymers and
assists in fundamental investigation of structure-property relationship. Properties
such as melting point, glass transition temperature, solubility, permeability, chemi-
cal reactivity and elasticity can be modified through graft copolymerisation as per
the specific requirements [
11
-
13
]. In recent years, modification of chemical and
physical properties of natural polymers and their derivatives through graft
copolymerisation has attracted much attention [
14
-
19
]. Graft copolymerisation of
various vinyl monomers onto different polysaccharides has been reported by
various workers. Since polysaccharides occur abundantly in nature, therefore, this
class of polymers is of special significance for the scientists. Polysaccharides have
wide applications in the field of food, cosmetics and pharmaceuticals [
20
-
24
].
In view of the importance of polysaccharides in various fields and their modifi-
cation through graft copolymerisation for their industrial applications, this chapter
deals with the different methods of graft copolymerisation of vinyl monomers onto
polysaccharides.
1.2 Polysaccharides
Polysaccharides are polymeric carbohydrate structures which are formed by repeat-
ing units joined together by glycoside linkages and contain various degrees of
branching. Polysaccharides have a general formula C
x
(H
2
O)
y
, where
y
is usually
a large number between 200 and 2,500. Starch and glycogen are storage
polysaccharides, whereas cellulose and chitosan act as the structural materials.
They provide mechanical strength to plants [
25
] which make them fit for
applications like fibres [
26
], films [
27
], adhesives [
28
], melt-processing plastics
[
29
], hydrogels [
30
], drug delivery agents [
31
] and emulsifiers [
32
].
Polysaccharides are bio-based materials possessing unique combination of func-
tional properties and environmental-friendly features. They are non-toxic, biode-
gradable and renewable materials. Commercially available products include starch,
