FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
AND
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2005
COMPLETE SPECIFICATION
(See section 10 and rule 13) TITLE OF THE INVENTION
SULFONATED POLY(BENZYL CINNAMATE-CO-MALEIC ANHYDRIDE) COPOLYMER AND A PROTON EXCHANGE FUEL CELL MEMBRANE THEREOF
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR
Chaudhari Sushil Ekanath of Crompton Greaves Ltd, Conition Monitoring & Diagnostic Centre, CG Global R&D Centre, Kanjur (E), Mumbai 400042, Maharashtra, India, Indian National
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed.

TECHNICAL FIELD OF INVENTION:
This invention relates to sulfonated poIy(benzyl cinnamate-co-maleic anhydride) copolymer and a process for the preparation thereof. Particularly, the sulfonated poIy(benzyl cinnamate-co-maleic anhydride) copolymer have high proton conductivity.
This invention also relates to a proton exchange membrane and a process for the preparation thereof. More particularly, the present invention relates to a proton exchange membrane having high proton conductivity and a process for the preparation thereof
This invention relates to a fuel cell having a proton-conducting polymer membrane between two electrodes where the proton-conducting polymer membrane comprising sulfonated poIy(benzyl cinnamate-co-maleic anhydride) copolymer according to the invention.
BACK GROUND AND PRIOR ART:
A proton exchange membrane conducts the positively charged species within the fuel cell. This membrane, which also blocks electrons, must remain hydrated to be functional and stable.
Proton conductive materials already known in the art include both organic as well as inorganic compounds.
Examples of organic compounds are organic polymers like sulfonated vinyl polymers, polybenzimidazole, perfluoroalkylcarboxylic polymers. Inorganic

compounds used as proton conductive materials include uranyl phosphates which form hydrates.
A major disadvantage of proton exchange membrane fuel cells is that they are typically expensive. It has been known that a major portion of the cost of a proton exchange membrane fuel cell is the proton exchange membrane. Therefore, it is desirable to provide a proton exchange membrane for use in proton exchange membrane fuel cells wherein the membrane is cost-effective.
The proton exchange membranes used in conventional proton exchange membrane fuel cells are aromatic based membranes which require frequent hydration to remain effective. Moreover, these aromatic based membranes typically swell upon losing hydration, which depreciates the proton exchange membrane fuel cell efficiency. The member must always remain hydrated in order to transfer the protons.
US 4450261 discloses a process for preparing a copolymer of styrene or substituted styrene and maleic anhydride in a solvent such that the resultant copolymer has a molecular weight in the range of about 500 to 10,000 and is substantially odorless. This patent further discloses a convenient and efficient process for preparing a sulfonated copolymer of styrene or substituted styrene and maleic anhydride which eliminates intermediate recovery, purification, and handling steps involved in the general styrene-maleic anhydride polymerization process before the sulfonation reaction. However, this patent does not teach a proton exchange membrane having a high proton conductivity that could find suitable application in proton exchange membrane fuel cell as an electrolyte.

US7601785 discloses a sulfonated multiblock copolymer, which comprises a hydrophilic block (X) having a repeating unit represented by a formula and a hydrophobic block (Y) having a repeating unit represented by another formula, wherein the number (m) of the repeating unit of first said formula in the hydrophilic block (X) and the number (n) of the repeating unit of second said formula in the hydrophobic block (Y) satisfy the conditions of 4 <= m <= 400 and 4 >= n >= 400. This patent discloses an electrolyte membrane obtamed from the sulfonated multiblock copolymer and a fuel cell using the electrolyte membrane.
A need remains in the art for a proton exchange membrane for use in proton exchange membrane fuel cell that overcomes the aforesaid problems existing in the art.
OBJECTS OF THE INVENTION:
An object of the invention is to provide a copolymer, sulfonated poly(benzyl cinnamate-co-maleic anhydride) having high proton conductivity.
Another object of the invention is to provide a copolymer, sulfonated poly(benzyl cinnamate-co-maleic anhydride) having high proton conductivity which is cost-effective.
Another object of the invention is to provide a process for the preparation of copolymer, sulfonated poly(benzyl cinnamate -co-maleic anhydride) having high proton conductivity where the process is simple and easy to carry out.

Another object of the invention is to provide a proton exchange membrane having high proton conductivity.
Another object of the invention is to provide a proton exchange membrane that remains hydrated for a longer period of time during the operation of the proton exchange membrane fuel cell.
Yet another object of the invention is to provide a proton exchange membrane that is economical and cost-effective.
Yet another object of the invention is to provide a proton exchange membrane that is durable and capable of operating at low temperature, preferably less than 100°C.
Yet another object of the invention is to provide a proton exchange membrane which does not degrade during the fuel cell operating cycle.
Still another object of the invention is to provide a proton exchange membrane which does not swell upon hydration.
Still another object of the invention is to provide a proton exchange membrane fuel cell which does not suffer from the aforesaid disadvantages.
These and other objects of the present invention are achieved by the remaining portion of the description.

SUMMARY OF THE INVENTION:
In one aspect, the invention provides sulfonated poly(benzyl cinnamate-co-maleic anhydride) copolymer having high proton conductivity.
In another aspect, the invention provides a process for the preparation of sulfonated poly(benzyl cinnamate-co-maleic anhydride) copolymer, said process comprising:
(a) copolymerizing benzyl cinnamate with maleic anhydride at 55 - 60° C to produce poly(benzyl cinnamate-co-malefic anhydride) copolymer;
(b) sulfonating said poly(benzyl cinnamate-co-maleic anhydride) copolymer.
In yet another aspect, the invention provides a proton exchange membrane comprising sulfonated poly(benzyl cinnamate-co-maleic anhydride) copolymer of the invention.
In yet another aspect, the invention provides a proton exchange membrane comprising sulfonated poly(benzyl cinnamate-co-maleic anhydride) copolymer of the invention and prepared by convention method such as casting, etc.
In yet another aspect, the invention provides a fuel cell which comprises a cathode comprising a catalyst that promotes a reduction of oxygen; an anode comprising a catalyst that promotes an oxidatipn of a fuel; and a proton exchange membrane interposed between the cathode and the anode; characterized in that the proton exchange membrane comprising sulfonated poly(benzyl cinnamate-co-maleic anhydride) copolymer of the invention.

BREIF DESCRIPITION OF THE ACCOMPANYING DRAWINGS;
Figure 1 illustrates IR of benzyl cinnamate,
Figure 2 illustrates IR of poly(benzyl cinnamate-co-maleic anhydride) copolymer.
Figure 3 illustrates IR of sulfonated poly(benzyl cinnamate-co-maleic anhydride) copolymer.
Figure 4 illustrates XRD of sulfonated poly(benzyl cinnamate-co-maleic anhydride) copolymer.
Figure 5 illustrates graph of TGA.
Figure 6 illustrates the graphical representation of conductivity of the sulfonated copolymers against temperature.
Figure 7 illustrates graphical representation of conductivity of sulfonated copolymer against temperature based on Arrhenius Equation.
Figure 8 illustrates Complex impedance spectrum for the sulphonated copolymer of the invention at temperature ranging from 30° to 150oC between silver electrodes.

DETAILED DESCRIPTION OF THE INVENTION:
According to the present invention, there is provided a sulfonated poly(benzyl cinnamate-co-maleic anhydride) copolymer which possesses high proton conductivity and remains hydrated for a longer period of time.
The sulfonated poly(benzyl cinnamate-co-maleic anhydride) copolymer according to the present invention is economical and cost-effective and is capable of operating at low temperature, preferably less than 100 C as well as sub-zero ambient conditions without degrading.
The aforesaid copolymer does not swell upon dehydration and provides an ideal proton exchange membrane for a proton exchange membrane fuel cell.
According to one embodiment of the present invention, there is provided sulfonated poly(benzyl cinnamate-co-maleic anhydride) copolymer having high proton conductivity.
According to another embodiment of the present invention, there is provided a process for the preparation of sulfonated poIy(benzyI cinnamate-co-maleic anhydride) copolymer, said process comprising:
(a) copolymerizing benzyl cinnamate ester with maleic anhydride to produce poIy(benzyl cinnamate-co-maleic anhydride) copolymer;
(b) sulfonating said poly(benzyl cinnamate-co-maleic anhydride) copolymer.
The reaction parameters for copolymerizing benzyl cinnamate with maleic anhydride is not particularly limiting and may be carried out using

conventional methods known in the art. However, the choice of monomers selected for preparing the copolymer, according to the present invention, i.e. benzyl cinnamate and maleic anhydride was found critical to achieve the aforesaid one or more advantages of the present invention. Likewise, the reaction parameters for sulfonating the poly(benzyl cihnamate-co-maleic anhydride) copolymer is not particularly limiting and may be carried out using conventional methods known in the art.
The benzyl cinnamate ester is copolymerized with maleic anhydride at 55° C to 60° C to produce poly(benzyl cinnamate-co-maleic anhydride) copolymer.
The benzyl cinnamate ester, poly(benzyl cinnamate-co-maleic anhydride) copolymer and sulfonated poly(benzyl cinnamate-co-maleic anhydride) copolymer were analyzed by IR spectrometry. The figure 1 illustrates IR of benzyl cirmamate ester and characteristic peaks are as follows:

Frequency (Reported) Frequency (Observed)
C=0 (Stretching) 1690-1760 1715
C—H (bending -CH2-) 1430-1470 1450
C—C (Stretching Arom.) 1500-1600 1500,1580
C—H (bending Arom.) 675-870 720
C—H (Stretching Arom.) 3000-3300 3300
C=C (Stretching Arom.) 1650 1639.03
C-C (Stretching) 2800-3000 2917, 2850
The figure 2 illustrates IR of poly(benzyl cinnamate-co-maleic anhydride) copolymer and characteristic peaks are as follows:

Frequency (Reported) Frequency (Observed)
C=O (Stretching) 1690-1760 1736.41
C—O 1000-1200 1174.46
C-4I (bending -CH2-) 1410-1470 1418
C—C (Stretching Arom.) 1500-1600 1540
C—H (bending Arom.) 675-870 720,684
C=C (Stretching Arom.) 1650 1608.1
C-H (Stretching) 2800-3000 2918,2849.79
The figure 3 illustrates IR of sulfonated poly(benzyl cinnamate-co-maleic anhydride) copolymer and characteristic peaks are as follows:

Frequency (Reported) Frequency (Observed)
C=0 (Stretching) 1690-1760 1735
c—0 1000-1200 1070,1174.29
C-H (bending-CHz-) 1430-1470 1454
C—C (Stretching Arom.) 1500-1600 1448
C—H (bending Arom,) 675-875 750.3,844.4
C-H (Stretching Arom.) 3000-3100 3004.13
O—H (Broad Band) 3200-3600 3433.38
C—H (Stretching) 2800-3000 2920,2958
The figure 4 illustrates XRD of sulfonated poly(benzyl cinnamate-co-maleic anhydride) copolymer and it is found that the sulfonated copolymer is amorphous in nature. XRD is a plot of intensity (I) against 20.
The figure 5 illustrates graph of TGA and it is found that the sulfonated copolymer is stable.

Sulfonated poly(benzyl cinnamate-co-maleic anhydride) copolymer is studied for its conductivity at varying temperature. The figure 6 illustrates the graphical representation of conductivity of the sulfonated copolymers against temperature and found that conductivity of the polymer increases with the decrease of temperature. The sulfonated copolymer has a proton conductivity of 33.96 Scm"' by using a pellet having cross sectional area 1.34x10-4 cm2 at30° C and is decreased to 5.9x10-5 Scm-1 at 150° C.
Yet another finding embodied in the present invention is that the sulfonated poly(benzyl cinnamate-co-maleic anhydride) copolymer of the present invention possessed a proton conductivity of 33.96 Scm"' at 30° C when incorporated within proton exchange membrane fuel cell.
According to another embodiment of the present invention, there is provided a proton exchange membrane comprising sulfonated poly(benzyl cinnamate-co-maleic anhydride) copolymer; the membrane has high proton conductivity. The membrane also remains hydrated for a longer period of time. The membrane is capable of operating at low temperature, preferably
less than 100 C as well as sub-zero ambient conditions without degrading.
The proton exchange membrane is prepared from sulfonated poly(benzyl cinnamate-co-maleic anhydride) copolymer of the invention by using conventional methods such as casting, film making, etc.
According to yet another embodiment of the present invention, there is provided a fuel cell which comprises a cathode comprising a catalyst that promotes a reduction of oxygen; an anode comprising a catalyst that promotes an oxidation of a fuel; and a proton exchange membrane

interposed between the cathode and the anode; characterized in that the proton exchange membrane comprising sulfonated poly(benzyl cinnamate-co-maleic anhydride) copolymer of the invention.
The sulfonated copolymer has a proton conductivity of 33.96 Scm"' at 30° C. Further, the raw materials used to prepare the sulfonated copolymer are readily available and cheap without affecting proton conductivity thereby making the copolymer of the invention cost-effective. The process for the preparation of copolymer, sulfonated poly(benzyl cinnamate-co-maleic anhydride) is simple and easy to carry out. It was observed that the proton exchange membrane of the invention remains hydrated for a longer period of time during the operation of the proton exchange membrane fuel cell. Thus, cost-effective copolymer of the invention makes the proton exchange membrane economical and cost-effective. The proton exchange membrane is durable and capable of operating at low temperature, preferably less than 100°C. Further it was observed that the proton exchange membrane of the invention does not degrade during the fuel cell operating cycle and does not swell upon hydration.
The following experimental examples are illustrative of the invention but not limitative of the scope thereof:
Example 1:
Benzyl cinnamate was prepared by reacting 0.46 moles of cinnamic acid and 0.23 moles of benzyl alcohol using 0.2 ml of sulfuric acid as a catalyst and 86 ml of dry toluene as a solvent. Water was separated azeotropically using Dean-Stark apparatus. After completion of reaction, the crude ester was

neutralized by concentrated sodium bicarbonate solution to remove acidity. The organic layer was separated and dried over anhydrous sodium sulphate and the solvent was recovered by vacuum distillation.
The benzyl cinnamate (0.20 mol) was copolymerized with double re-crystallized maleic anhydride (0.20 mol) in 1:1 mole ratio in 67 ml of dry benzene under nitrogen atmosphere with 0.7% by weight of total monomers of Azobisisobutyronitrile (AIBN) as an initiator at 55 to 66oC with constant stirring. After completion of reaction, excess benzene was distilled off under reduced pressure. Then, purification of copolymer was effected by repeated solvent non-solvent method (Benzene-methanol) and traces of solvent were removed by drying under reduced pressure at 50°C / 25 mm Hg for 12 hours.
5gm of the said copolymer was dissolved in 10 ml of dichloro methane. To this mixture, 2.5 ml of CISO3H and 2.5 ml of distilled water was added drop wise with continuous stirring under reflux conditions for 15 minutes to get a solid cream colored sulphonated product. It was washed with distilled water to remove excess acid present until the water after washing is neutral.
The sulfonated copolymer was analysed by IR, XRD and TGA.
Figure 3 illustrates IR of sulfonated poly(benzyl cinnamate-co-maleic anhydride) copolymer and characteristic peaks are as follows:

Frequency (Reported) Frequency (Observed)
C=O (Stretcbiag) 1690-1760 1735
C—O 1000-1200 1070,1174.29
C—H (bending -CH2-) 1430-1470 1454

C—C (Stretching Arom.) 1500-1600 1448
C—H (bending Arom.) 675-875 750.3,844.4
C-H (Stretching Arom.) 3000-3100 3004.13
O—H (Broad Band) 3200-3600 3433.38
C—H (Stretching) 2800-3000 2920,2958
Figure 4 illustrates XRD of sulfonated-(poly-(benzyl cinnamate ester-co-maleic anhydride) copolymer and found that the sulfonated copolymer is amorphous in nature.
The figure 5 illustrated graph of TGA and found that the sulfonated copolymer is stable.
The copolymer prepared according to the invention is used to prepare the proton exchange membrane by casting. It is used in the fuel cell and its conductivity behavior is studied at different temperatures ranging from 30 to 150° C by using a pellet of cross sectional area 1.34x100-4 cm2. The conductivity results were shown in table 1.
Table 1: Results of conductivity of the sulfonated copolymer at varying temperatures

Temp (oC) Temp(K) 1/T(K-1) R(Ω) σ (S cm-1) Log σ
30 303 0.0033 11.163 33.96332 1.53101
35 308 0.00325 58.033 6.53305 0.81512
40 313 0.00319 55.765 6.79875 0.83243
50 323 0.0031 44.125 8.59224 0.93411
60 333 0.003 106.01 3.57638 0.55344
70 343 0.00292 263.03 1.4414 0.15879
80 353 0.00283 89206 0.00425 -2.3716
90 363 0.00275 1.0449E6 3.62841E-4 -3.44028
100 373 0.00268 8.7609E6 4.32755E-5 -4.36376
110 383 0.00261 2.9534E7 1.28372E-5 -4.89153
120 393 0.00254 1.4053E7 2.69788E-5 -4.56898
130 403 0.00248 1.3214E7 2.86917E-5 -4.54224
140 413 0.00242 9.9757E6 3.80056E-5 -4.42015
150 423
- 0.00236 6.4192E6 5.90623E-5 -4.22869
Figure 6 illustrates graphical representation of conductivity of sulfonated copolymer against temperature. The graph shows the results obtained for the sulfonated copolymer are varying with temperature and found that it is inversely proportional to temperature i.e. as the temperature increases, conductivity decreases. At the low temperature (i.e. 30° C), it shows high conductivities of approximately 33.96 Scm'^ by using a pellet of cross sectional area 1.34x10-4 cm2 and with the same pellet as the temperature increases up to 150°C the conductivity decreases to 5.9x10-5 Scm-1. The conductivity is calculated by the formula,
σ = (1/R)(L/A)
Where, A= Area of the pellet in cm2 R= Resistance

L=Length
Figure 7 illustrates graphical representation of conductivity of sulfonated copolymer against temperature based on Arrhenius Equation.
This graph relates log (a) vs. I/T according to the Arrhenius Equation -
. -E/w
σ— σ.e
Log σ =log σo-E/CT
where, Σ0 = constant
E = activation energy
K=rate constant
Hence, Arrhenius Equation becomes -Log σ oc 1/T
The temperature dependence of the conductivity of polymer electrolyte here indicates a deactivated process. Thus the conductivity decreases with increasing temperature, and Arrhenius behavior provides a good representation in Figure 7.
Figure 8 illustrates Complex impedance spectrum for the sulphonated copolymer of the invention at temperature ranging from 30° to 150oC between silver electrodes. Here Z" is the imaginary impedance and Z' is the real impedance. The bulk resistance of the electrolyte (Rb) can be derived from this Cole-Cole plot. The value for the resistance of the sample (Rb) along with thickness of the sample and electrode area yields the resistivity of the sample or its inverse, the conductivity. σ = (1/R)(L/A)

Here; in this graph variation of real impedance vs. frequency is shown for different temperatures. It can be concluded from the graph (figure 8) that as the frequency increases real impedance decreases.
The invention has been described with reference to the aforesaid specific examples. It should be noted that the example(s) appended above illusfrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the present invention.

We Claim;
1. Sulfonated poly(benzyl cinnamate-co-maleic anhydride) copolymer having high proton conductivity.
2. The copolymer as claimed in claim 1 wherein the copolymer has a proton conductivity of 33.96 Scm-1 at 30°C and remains hydrated.
3. A process for the preparation of Sulfonated poly(benzyl cinnamate -co-maleic anhydride) copolymer, said process comprising:

(a) copolymerizing benzyl cinnamate ester with maleic anhydride at 55°C to 60° C to produce poly(benzyl cinnamate-co-maleic anhydride) copolymer;
(b) sulfonating said poIy(benzyl cinnamate-co-maleic anhydride) copolymer.

4. A proton exchange membrane comprising sulfonated poly (benzyl cinnamate-co-maleic anhydride) copolymer of claim 1.
5. The membrane as claimed in claim 4 wherein the membrane has proton conductivity of 33.96 Scm-1 at 30°C and remains hydrated.
6. A fuel cell comprising
a. a cathode comprising a catalyst that promotes a reduction of
oxygen;
b. an anode comprising a catalyst that promotes an oxidation of a
fuel; and

c. a proton exchange membrane interposed between the cathode and the anode;
characterized in that the proton exchange membrane comprising Sulfonated poly(benzyl cinnamate-co-maleic anhydride) copolymer of claim 1.