152
P. Wankhade et al.
The homogenization has been done for 30 min, and 5 min of break has been given
after every 10 min of stirring to allow the particles to settle.
4.3 Nanoemulsion Application Through Layer by Layer
Technique
Preparation of polyelectrolyte solution: Two polyelectrolyte solutions are prepared
with the aid of a magnetic stirrer at room temperature. These polyelectrolytes are used
in the LBL application technique, where oil nanoemulsion will be attached on fabric
due to surface ionic bonding. The first solution contains 0.1 % polyethyleneimine
(cationic polyelectrolyte), branched having molecular weight 25,000. The pH of
polyelectrolyte solution is adjusted to 7 using 1 M HNO 3 . The second solution
contains 0.1 % polyacrylic acid (anionic polyelectrolyte) having molecular weight
450,000. The pH is adjusted to 5 using 1 M HNO 3 [4].
PAA contains carboxylic acid repeat unit that dissociates to form negatively
charged anion in low pH aqueous solutions. With the increase in pH, the polymer
chain becomes increasingly ionized, the building negative charge constrains further
deprotonation, and the pKa, the dissociation constant value of PAA, alters. PAA
adopts a relatively smooth swelling process in the pH range of 4–6. As the degree
of ionization increased from pH 4 to 6, the equivalent deprotonation and subsequent
anionic charge drive PAA to adopt an extended state with a relatively smooth transition, with only small changes to polymer physical properties that save additional
anionic potential [7]. Thus, the pH of polyacrylic acid is adjusted to 5.
Application of Oil Nanoemulsion through LBL Technique: Fabric is immersed
into a beaker containing a solution of cationic polyelectrolyte which results in activation of functional groups on the outer surface, that is, attachment of first layer. Cotton
fabric has negative charge when immersed in water, thus when it is first dipped in the
solution of cationic solution, positive charges from the cationic solution would easily
bond with the negative charge on the cotton substrate. Thus, the fabric has been first
dipped in the solution of positive polyelectrolyte solution for 2 min. A washing step
with distilled water is followed to remove the loosely adhered polyelectrolyte. The
fabric is then dipped into a beaker containing solution of negative polyelectrolyte and
oil nanoemulsion for 2 min. This is again followed with a washing step to remove
the loosely deposited electrolytes. The cycle is repeated till the required number of
layers are obtained. The number of layers is the number of times the cycle of dipping
the fabric into alternate solutions of polyelectrolyte is repeated. When the fabric
is dipped into alternate solutions of polyelectrolytes, multilayers are spontaneously
deposited on the fabric surface through strong electrostatic formation. The finished
sample is air dried at room temperature and stored in an airtight bag [3].
Trials have been conducted using 50 and 100 g/l of nanoemulsion concentration
in the negative polyelectrolyte solution. The nanoemulsion is added in the negative
polyelectrolyte solution as the oil would easily get attached from the anionic solution
P. Wankhade et al.
The homogenization has been done for 30 min, and 5 min of break has been given
after every 10 min of stirring to allow the particles to settle.
4.3 Nanoemulsion Application Through Layer by Layer
Technique
Preparation of polyelectrolyte solution: Two polyelectrolyte solutions are prepared
with the aid of a magnetic stirrer at room temperature. These polyelectrolytes are used
in the LBL application technique, where oil nanoemulsion will be attached on fabric
due to surface ionic bonding. The first solution contains 0.1 % polyethyleneimine
(cationic polyelectrolyte), branched having molecular weight 25,000. The pH of
polyelectrolyte solution is adjusted to 7 using 1 M HNO 3 . The second solution
contains 0.1 % polyacrylic acid (anionic polyelectrolyte) having molecular weight
450,000. The pH is adjusted to 5 using 1 M HNO 3 [4].
PAA contains carboxylic acid repeat unit that dissociates to form negatively
charged anion in low pH aqueous solutions. With the increase in pH, the polymer
chain becomes increasingly ionized, the building negative charge constrains further
deprotonation, and the pKa, the dissociation constant value of PAA, alters. PAA
adopts a relatively smooth swelling process in the pH range of 4–6. As the degree
of ionization increased from pH 4 to 6, the equivalent deprotonation and subsequent
anionic charge drive PAA to adopt an extended state with a relatively smooth transition, with only small changes to polymer physical properties that save additional
anionic potential [7]. Thus, the pH of polyacrylic acid is adjusted to 5.
Application of Oil Nanoemulsion through LBL Technique: Fabric is immersed
into a beaker containing a solution of cationic polyelectrolyte which results in activation of functional groups on the outer surface, that is, attachment of first layer. Cotton
fabric has negative charge when immersed in water, thus when it is first dipped in the
solution of cationic solution, positive charges from the cationic solution would easily
bond with the negative charge on the cotton substrate. Thus, the fabric has been first
dipped in the solution of positive polyelectrolyte solution for 2 min. A washing step
with distilled water is followed to remove the loosely adhered polyelectrolyte. The
fabric is then dipped into a beaker containing solution of negative polyelectrolyte and
oil nanoemulsion for 2 min. This is again followed with a washing step to remove
the loosely deposited electrolytes. The cycle is repeated till the required number of
layers are obtained. The number of layers is the number of times the cycle of dipping
the fabric into alternate solutions of polyelectrolyte is repeated. When the fabric
is dipped into alternate solutions of polyelectrolytes, multilayers are spontaneously
deposited on the fabric surface through strong electrostatic formation. The finished
sample is air dried at room temperature and stored in an airtight bag [3].
Trials have been conducted using 50 and 100 g/l of nanoemulsion concentration
in the negative polyelectrolyte solution. The nanoemulsion is added in the negative
polyelectrolyte solution as the oil would easily get attached from the anionic solution