Read properties of the polymer, choose polymer 

polymer has to with stand in at least 70 oc, has do absorb water not up to swelling level

solvent has to choose

wt% has to optimize

use solution casting method...time,temperature, wt% polymer,volume of the solution, thickness of the membrane u have consider

then make a film...and use it for fuel cell application...your membrane has to conduct proton less swelling with high water uptake.

All the best 

Thank You Dr. Meenakshi, Can you support me with any detailed Example of the membrane preparation and fuel application.

For polymer electrolyte membrane fuel cells Nafion membranes have been the standard so far.. However, many innovations and modifications are being carried out.. You can check these publications.. May be you will find them useful.. Best of luck..

http://www.sciencedirect.com/science/article/pii/S0376738814007030

http://www.sciencedirect.com/science/article/pii/S0376738814004256

http://www.sciencedirect.com/science/article/pii/S0306261914002050

http://www.sciencedirect.com/science/article/pii/S0306261913010283

http://www.tandfonline.com/doi/abs/10.1080/15583724.2013.839566

http://www.sciencedirect.com/science/article/pii/S0306261913005965