4
58
P. Dutta et al. / Reactive & Functional Polymers 73 (2013) 457–464
2
. Experimental
2.6. Transport number determination
2
.1. Materials
The total ionic transport number, tion was evaluated by the stan-
dard Wagner polarization technique. The cell SS/(Polymer)/SS (SS
stands for Stainless Steel) was polarized by a step potential (about
1 V) and the resulting potentiostatic current was monitored as a
function of time. The two stainless steel plates act as blocking elec-
trodes for the above cell. The tion was evaluated using the formula:
Cis-9-octadecen-1-ol (MERCK), methacrylic acid (SPECTRO-
CHEM), p-toluene sulphonic acid (LOBA CHEMIE), ethylmethylke-
tone (MERCK), 1-hexene (SPECTROCHEM), ethylene glycol
dimethacrylate (MERCK) were used without further purification.
t
ion = (i
t
ꢀ i
e t t e
)/i , where i and i are total and residual current
respectively.
2
.2. Synthesis of co-polymers with acrylic acid
In addition to the percentage electronic character of the poly-
mers we also collected the XRD plots (Fig. S1) verifying amorphous
nature of the gels and the change in conductivity of the gels
About 0.03 mol (9.57 ml) of cis-9-octadecen-1-ol, 0.03 mol
(
2.5 ml) of acrylic acid, 0.05 g of p-toluenesulphonic acid were
(Fig. S2) with increase in temperature. These plots are given in
heated together for 30 min at 100–110 °C. After that 0.03 mol 1-
hexene (1:1) was added to the reaction mixture along with
the supplementary information.
0
.5 ml of ethylene glycol dimethacrylate (EGDMA, crosslinker)
2
.7. Swelling measurements
and allowed to react at 100–120 °C for 4 days. We have chosen
thermal polymerization to avoid the use of any external agent.
The above reaction was repeated with 0.06 mol 1-hexene (1:2)
mol ratio. The products obtained were washed with ethylmethylk-
etone and then vacuum dried to give 8 g and 8.2 g of soft yellow
polymeric gels of poly-9-octadecenylacrylate-co-hexene. The co-
polymers having 1:1 and 1:2 mole ratios of 9-octadecenylacrylate
and 1-hexene were labeled as PODAH1 and PODAH 2 respectively.
The swelling measurement of the co-polymer gels was carried
out in different polar/nonpolar solvents such as water, ethanol,
acetone, tetrahydrofuran, diethylether, dichloromethane, chloro-
form, benzene, toluene, thiophene, furan, and pyridine, respec-
tively, by gravimetric methods. For this purpose,
a known
amount of polymer sample was placed in a bag (made of filter pa-
per) and immersed in a solvent. The weight of the filter paper bag
was taken before placing the sample in it. The bags were taken out
at different intervals of time (15 min, 30 min, 45 min, 60 min,
2.3. Synthesis of co-polymers with methacrylic acid
9
0 min and 120 min, respectively), blotted quickly to remove ex-
0
.03 mol (9.57 ml) of cis-9-octadecen-1-ol, 0.03 mol (3 ml) of
cess solvent, and weighed in a stoppered bottle. The swelling
experiments were carried out at different temperature ranges i.e.,
0
methacrylic acid, 0.05 g of p-toluenesulphonic acid were heated to-
gether for 30 min at 100–110 °C. After that 0.03 mol 1-hexene
along with 0.5 ml of EGDMA (cross linker) was added to the reac-
tion mixture and allowed to react at 100–120 °C for 4 days. The
same experiment was repeated with 0.06 mol 1-hexene (1:2) mol
ratio. The products obtained were washed with ethylmethylketone
and then vacuum dried to give 8.1 g and 8.2 g of soft yellow poly-
meric gels of poly-9-octadecenylmethacrylate-co-hexene. The co-
o-polymers with 1:1 and 1:2 molar ratios were labeled as POD-
MAH1 and PODMAH 2 respectively.
°C, 25 °C and 50 °C, respectively.
The swelling capacity can be calculated by the following
formula:
ꢀW ꢀ Wꢁ
t
Swelling capacity ¼
ꢁ 100%
ð1Þ
W
t
where W is the weight of the swollen gel at time t and W is the
weight of the dry sample.
The swelling capacities were also calculated for the gels in dif-
ferent oils, such as, kerosene, gasoline, engine oil (SAE 30), and sil-
icon oil (DC 704). The known amount of dry gels were placed in
different oils and left for 24 h. Then the gels were wiped with a
blotting paper and their weights were recorded. An experiment
showing the removal of kerosene by the co-polymer gel PODAH
from water/kerosene mixture was also performed to prove their
future applicability as water purifiers.
Temperature dependence of swelling in the above solvents and
oils was measured at different temperatures i.e. 0 °C, 25 °C and
5
and kept at different temperatures until the swelling reached the
equilibrium. The gels were taken out at different intervals of time
and their weights were measured. Due to low boiling points, the
swelling properties of the gels in solvents like tetrahydrofuran,
chloroform, dichloromethane, and ether were not checked at 50 °C.
2
.4. Characterization
Fourier Transform Infrared Spectra of the monomers 9-octade-
cenylacrylate (ODA), 9-octadecenylmethacrylate (ODMA) and the
co-polymers poly-9-octadecenylacrylate-co-hexene (PODAH1, PO-
DAH2) and poly-9-octadecenylmethacrylate-co-hexene (POD-
MAH1, PODMAH2) were recorded with a Bruker Vector 22 FT-IR
ꢀ1
spectrophotometer in the range of 400–4000 cm . The FT-IR spec-
tra for the monomers were taken in the form of liquid. The polymer
samples for FT-IR measurements were prepared in the form of pel-
lets by mixing about 20 mg of IR spectroscopic grade potassium
bromide with about 2 mg of dried samples. The spectra were re-
corded in transmission mode over 64 scans. The Thermogravimet-
ric analysis (TGA) of the polymers was carried out using Perkin
Elmer TGA 4000 at the heating rate 10 °C/min and with a nitrogen
flow rate of 20 ml/min. The solubility of the polymers was checked
in different polar and nonpolar solvents.
0 °C respectively. The sample was placed in the above solvents
2.8. Kinetic studies
For kinetic studies, the solvent absorption capacities were mea-
2
.5. Morphological studies
sured by immersing a known amount of dry gel in polar/nonpolar
solvents and then taking the weight of the swollen gel at different
intervals of time (15 min, 30 min, 45 min, 1 h, etc.). Longer immer-
sion times leads to greater absorption until the saturation point is
reached. Thus we checked the swelling kinetics for all the gels [26].
For first order kinetics, the swelling is expressed as shown in the
following equation:
Square shaped gels of size about 2 mm height were dried in a
desiccator and considered for surface studies. The surface mor-
phology of the gels was determined by SIGMA-VP (ZEISS) Scanning
Electron Microscope at an accelerating voltage of 5 kV and at a con-
stant magnification of 2000ꢁ. All the samples were gold coated be-
fore SEM analysis.