Presentation On Polymer Gels (Hydrogels).

1. Presented by
Devansh Gupta
M.Sc. Polymer Science
Semester 4

2. • Polymer gel is a water-swollen, and cross-linked polymeric network produced by the simple
reaction of one or more monomers.
OR
• Polymer gel is a polymeric material that exhibits the ability to swell and retain a significant
fraction of water within its structure, but will not dissolve in water.
OR
• Polymer gels are macromolecular structure constructed of a cross linked water insoluble
polymeric network that has capacity to absorb large amount of water.
• The ability of polymer gels to absorb water arises from hydrophilic functional groups attached
to the polymeric backbone, while their resistance to dissolution arises from cross-links
between network chains.
• After the absorption of water these gels can expand up to 1000 times in volume.
Definition
• Hydrogels have become very popular due to their unique properties such as
high water content, softness, flexibility and biocompatibility.

3. • Polymer gels can be classified on different bases as detailed
below.
a) Classification based on source - Natural or synthetic origin
b) Classification based on polymeric composition
c) Classification based on type of cross-linking
d) Classification based on physical appearance
e) Classification according to network electrical charge
ClassificationOf Polymer Gels

4. • The method of preparation leads to formations of some different classes of
polymer gels which are shown below.
a) Homopolymeric polymer gels – Here the polymer network is derived
from a single species of monomer. They may have cross-linked skeletal
structure depending on the nature of the monomer and polymerization
technique.
b) Copolymeric polymer gels – Here the polymer network is comprised of
two or more different monomer species with at least one hydrophilic
component, arranged in a random, block or alternating configuration.
c) Multipolymer Interpenetrating polymeric gels – Here The polymer
network is made of two independent cross-linked synthetic and/or
natural polymer component. In semi-IPN polymer gel, one component is
a cross-linked polymer and other component is a non-cross-linked
polymer.
Classification Based On Polymeric Composition

5. • Polymer gels can be divided into two categories based on the chemical or
physical nature of their cross-link junctions.
• Chemically cross-linked networks have permanent junctions, while
physical networks have transient junctions that arise from either polymer
chain entanglements or physical interactions such as ionic interactions,
hydrogen bonds, or hydrophobic interactions
Classification Based On type of cross-linking
Classification Based On Physical Appearance
• The classification of polymer gels depends on their physical structure and
chemical composition can be classified as follows.
a) Amorphous (non-crystalline)
b) Semicrystalline - mixture of amorphous and crystalline phases
c) Crystalline

6. • Polymer gels are classified into four groups on the basis of
presence or absence of electrical charge located on the cross-
linked chains.
a) Non-ionic (neutral)
b) Ionic (anionic or cationic)
c) Amphoteric electrolyte (containing both acidic and basic
groups)
d) Zwitterionic (containing both anionic and cationic groups in
each structural repeating unit)
Classification Based On Electrical Charge

7. • Polymer gels can be synthesized by different polymerization methods such
as chain growth polymerization, addition and condensation polymerization
and gamma and electron beam polymerization which are shown below.
Synthesis
• Chain-growth polymerization includes free radical polymerization, controlled
free radical polymerization, anionic and cationic polymerization.
• In which free radical & controlled free radical polymerization is done by
three process viz., initiation, propagation, and termination. After initiation, a
free radical active site is generated which adds monomers in a chain link-
like fashion.
• Controlled living radical polymerizations offer the benefits of longer growing
chain compared to free radical polymerizations.
• While Anionic and Cationic polymerization methods suffer from extreme
sensitivity toward aqueous environments and therefore, are not widely used.

8. • In addition and condensation polymerization monomers can be
converted into polymer gels using crosslinking agents such as
Tetramethylethylenediamine.
• Here polymer chains are crosslinked in the presence of water to
form a polymer gel. In which water occupies voids in the
network, and give the polymer gel its characteristic surface
properties.
EX - Polyurethanes, polyesters, or nylon polymers are most
commonly synthesized for polymer gel applications.
• Gamma and electron beam polymerization involves high energy
electromagnetic irradiation as crosslinker.
• During irradiation, Hydroxyl radicals are formed and initiate free radical
polymerization among the monomers which propagate in a rapid chain
addition fashion and creates network of polymer gel.
• This process has an advantage over other crosslinking methods since it can
be performed at room temperature without using toxic and hard to remove
crosslinking agents such as Tetramethylethylenediamine.

9. Applications
Polymer
Gel

10. That’s All From Me..