Membrane separation technology is one of the most innovative and steadily growing fields across science and engineering. The performance of a membrane is determined by several key properties: high selectivity and permeability; excellent chemical, thermal, and mechanical stability under the process operating conditions; low maintenance; good space efficiency; and defect free conditions. The most commonly used membrane in fuel cell technology is Nafion, which relies on liquid water humidification of the membrane to transport protons. This implies that it is not feasible to use temperatures above 80-90 , since the membrane would dry. Recent studies on the surface modification of Nafion membranes involved doping with other polymers, plasma treatment, and electron beam treatment. In this... study, modification of Nafion was done using conducting polymer such as poly(dipheylamine) (PDPA) to reduce the methanol crossover in direct methanol fuel cell applications.