INTERCALATION AND EXFOLIATION

1. ANJANA S PANICKER
2ND M.Sc BPS
CBPST, KOCHI

2. INTRODUCTION
• The term ‘intercalation’ refers to a process whereby a guest molecule or ion is
inserted into a host lattice.
• The structure of the guest–host or intercalation compound is only slightly
perturbed from the host structure and the reaction used to form the compound is
reversible.
• Reactions involve adsorption of guest species on host crystals, exchange or
insertion at the host surface, the formation of intermediate stages in layered
compounds.
• A famous example is the intercalation of potassium into graphite.
• In extreme case of intercalation is the complete separation of the layers of
the material. This process is called ‘exfoliation’.
Typically aggressive conditions are required involving highly polar solvents
and aggressive reagents.
• Nano-composite material encompass a large variety of systems such as
one-dimensional, two-dimensional, three-dimensional and amorphous
materials, made of distinctly dissimilar components and mixed at the
nanometer scale.

3. • Inorganic layered materials exist in great variety. They possess well defined,
ordered intralamellar space potentially accessible by foreign species. This ability
enables them to act as matrices or hosts for polymers, yielding interesting hybrid
nano-composite materials.
• Lamellar nano-composites can be divided into two distinct classes, intercalated
and exfoliated.
• In intercalation the polymer chains alternate with the inorganic layers in a fixed
compositional ratio and have a well defined number of polymer layers in the
intralamellar space.
• The principle geometrical transitions of layered host lattice matrixes upon
intercalation of guest species include change in interlayer spacing,change in stacking
mode of the layers, and formationof intermediate phases at low guest concentrations
that mayexhibit staging.
• The intercalated nano-composites are also more compound-like because of
the fixed polymer/layer ratio, and they are interesting for their electronic and
charge transport properties.
• In exfoliated nano-composites the number of polymer chains between the layers
is almost continuously variable and the layers stand >100 Å apart. Exfoliated nano-
composites are more interesting for their superior mechanical properties.

4. POLYMER/CLAY NANOCOMPOSITE STRUCTURE
• In general, the structures of polymer/clay nanocomposites are classified according to
the
level of intercalation and exfoliation of polymer chains into the clay galleries.
• Various parameters including clay nature, organic modifier, polymer matrix and
preparation
method are affective on the intercalation and exfoliation level.
• Therefore depending on the nature and properties of clay and polymer as well as
preparation methodology of nanocomposite, different composite micro-structures can be
obtained.
1. Intercalated structure
• When one or more polymer chains are inserted into the inter layer space and cause to
the increasing of the inter layer spacing, but the periodic array of the clay layer is still
exist, the intercalated nanocomposite is formed.
• The presence of polymer chains in the galleries causes to the decreasing of
electrostatic forces between the layers but it is not totally dissolved.
• A well-ordered multilayer hybrid morphology with a high interference interactions
consisted of polymer chains and clay layer is obtained in this configuration.

5. 2. Exfoliated structure
• Exfoliated or delaminated structure is obtained when the insertion of polymer
chains into the clay galleries causes to the separation of the layers one another
and individual layers are dispersed within the polymer matrix.
• At all, when the polymer chains cause to the increasing of interlayer spacing
more than 80-100 Å, the exfoliated structure is obtained.
• Due to the well dispersion of individual clay layers, high aspect ratio is obtained
and lower clay content is needed for exfoliated nanocomposites.
• Also most significant improvement in polymer properties is obtained due to the
large surface interactions between polymer and clay.
3. Phase separated structure
• When the organic polymer is interacted with inorganic clay (unmodified clay), the
polymer is unable to intercalate within the clay layers and the clay is dispersed as
aggregates or particles with layers stacked together within the polymer matrix.
• The obtained composite structure is considered as “phase separated”.
• The properties of phase separated polymer/clay composites are in the range of
traditional micro composites.

7. Nanocomposite materials based on polyurethane intercalated into montmorillonite clay
• Polyurethane organoclay nanocomposites have been synthesized via in situ
polymerization method.
• The organoclay has been prepared by intercalation of diethanolamine or triethanolamine
in
to montmorillonite clay (MMT) through ion exchange process.
• The syntheses of polyurethane–organoclay hybrids were carried out by swelling the
organoclay into different kinds of diols followed by addition of diisocyanate.
• The nanocomposites with dispersed structure of MMT was obtained as evidence by
scanning electron microscope and X-ray diffraction (XRD)
Preparation of Nanocomposite Based on Exfoliation of Montmorillonite in
Acrylamide Thermosensitive Polymer
• Exfoliated nanocomposite based on thermosensitive polymer (PNIPAM) was prepared
utilizing montmorillonite (MMT) by solution blending. Its dispersion characteristics were
investigated using SEM, X-ray diffraction, and particle size analysis.

8. • XRD showed exfoliation of MMT in polymer matrix above lower critical solution
temperature (LCST).
• SEM indicated that polymer chains were dispersed among the layers of MMT.
Particle size analysis showed two distinctive regions at 311 (31/5%) and 1160
(68/5%) nm.
Nanocomposite materials: polyaniline-intercalated layered double hydroxides
• Open lamellar systems such as layered double hydroxides (LDHs) can be used to
generate new intercalation compounds.
• The oxidising host matrixes used as hosts for the interlamellar oxidative
polymerisation of aniline were
[Cu(1 –x)
2+Crx
3+(OH)2]·[(C6H4-1,4-(CO2)2)x/2
2–·nH2O] and
[Cu(1x)
2+Alx
3+(OH)2]·[(Fe(CN)6)x/4
4–·nH2O]
• The synthesis of nanocomposite materials consisting of organopolymer
molecules encapsulated between ultra-thin mixed-metal hydroxide sheets which
are propped apart by spacers [terephthalate or hexacyanoferrate(II) ions acting
as pillars] have been reported.

9. Aluminosilicate Nanocomposite Materials. Poly(ethylene glycol)−Kaolinite
Intercalates
• Involves the direct intercalation of an organic polymer into the interlamellar
spaces of kaolinite.
• Poly(ethylene glycols) (PEG 3400 and PEG 1000) were intercalated into kaolinite
by displacing dimethyl sulfoxide (DMSO) from the DMSO−kaolinite intercalate
(Kao−DMSO). This was done directly from the polymer melt at temperatures
between 150 and 200 °C.
• XRD showed that the intercalated oxyethylene units were arranged in flattened
monolayer arrangements, such that the interlayer expansion was 4.0 Å.
Biopolymer−Clay Nanocomposites Based on Chitosan Intercalated in
Montmorillonite
• The intercalation of a chitosan bilayer in Na+−montmorillonite through cationic
exchange and hydrogen-bonding processes turns the resulting nanocomposite into an
anionic exchanger, applied in the development of potentiometric sensors that show a
remarkable selectivity toward monovalent anions due to the special arrangement of
the biopolymer as a nanostructured bidimensional system.

10. • The first chitosan layer is adsorbed through a cationic exchange procedure, while
the second layer is adsorbed in the acetate salt form. Because the deintercalation of
the biopolymer is very difficult, the −NH3
+Ac- species belonging to the chitosan
second layer act as anionic exchange sites and, in this way, such nanocomposites
become suitable systems for the detection of anions.
• These materials have been successfully used in the development of bulk-
modified electrodes exhibiting numerous advantages as easy surface renewal,
ruggedness, and long-time stability. The resulting sensors are applied in the
potentiometric determination of several anions, showing a higher selectivity toward
monovalent anions.

11. Lamellar polysilicate nanocomposite materials: Intercalation of polyethylene
glycols into protonated magadiite
• The direct intercalation of organic polymers into the interlamellar
spaces of the layered polysilicate magadiite have been reported.
• Poly(ethylene glycols) (PEG 3400 and PEG 1000) were intercalated
into acidified magadiite (H-magadiite) by displacing a dipolar aprotic
solvent (e.g., dimethylsulfoxide (DMSO)) from the H-magadiite –DMSO
intercalate.
• This was done directly from the polymer melt at 155°C. The polysilicid
acid (H-magadiite) was obtained by HCl titration of the sodic form of
magadiite obtained by hydrothermal synthesis.
• Dipolar aprotic solvents (dimethylsulfoxide, N-methylformamide, and
hexamethylphosphorictriamide) were intercalated in the interlamellar spaces
of H-magadiite. PEG 3400 and PEG 1000 were then intercalated by
dispersing the H-magadiite intercalates in a large excess of the polymers
heated above their fusion temperature, without any solvent.
• The resulting polymer intercalated H-magadiite nanocomposites were
isolated and purified .

12. Preparation and properties of exfoliated nanocomposites through intercalated a
photoinitiator into LDH interlayer used for UV curing coatings
• The exfoliated polymer/layered double hydroxide (LDH) nanocomposites based
on MgAl were prepared through intercalating a photoinitiator into LDH interlayer,
following by UV irradiation induced polymerization.
• The fragmental photoinitiator, 2-hydroxy-2-methyl-1-phenylpropane-1-one (1173)
firstly reacted with isophorone diisocyanate (IPDI) to obtain the semiadduct, 1173-
IPDI, and then reacted with the LDH modified by aminoundecanoic acid, obtaining
LDH-1173 with an intercalated microstructure.
• The obtained LDH-1173 was mixed with the multifunctional acrylate oligomer and
monomer, and then exposed to a UV lamp to prepare a polymer/LDH
nanocomposite.
•
Compared with the pure polymer material, both the exfoliated and intercalated
polymer/LDH nanocomposites exhibited the enhancements in mechanical and
thermal properties, as well as hardness.

13. Intercalated PS/Na+-MMT Nanocomposites Prepared by Ultrasonically
In Situ Emulsion Polymerization
• Ultrasonically initiated in situ emulsion polymerization, was employed to
prepare intercalated polystyrene/Na+-MMT nanocomposites.
• FTIR, XRD, and TEM results confirm that the hydrophobic PS can easily
intercalate into the galleries of hydrophilic montmorillonite via ultrasonically
initiated in situ emulsion polymerization.
• The glass transition temperature of nanocomposites increased as the
percentage of clay increased, although the average molecular weight of PS
decreased, and the decomposition temperature of the 1obtained
nanocomposites moves to higher temperature.

14. APPLICATIONS
 Potentiometric sensors
 Energy storage
 Sensors
 Actuators
 Transistors