The proton exchange membrane fuel cell (PEMFC) is considered to be the most promising power source for portable and automotive applications. Currently, perfluorinated polymers such as Nafion are the state of the art materials because of their good physical and chemical stability along with high proton conductivity under a wide range of relative humidity at moderate operation temperatures. However, high operation temperatures, cause weakening of their properties. In addition, their shortcomings such as high cost and high methanol permeation property, limit their application. To remedy these problems, aromatic hydrocarbon polymers have been extensively studied as alternative materials for proton exchange membranes (PEMs)and many sulfonated aromatic polymers such as poly(phenylene)poly(ether ether ketone)s, poly(ether ether sulfone) poly(arylene ether) and polyimides have been developed as alternate candidates. Generally, membranes based on these polymers can achieve high proton conductivity by increasing their ion exchange capacities (IECs), resulting in huge water uptake and a dramatic loss of mechanical properties. Recently, introduction of block copolymer structures to PEMs has been considered as a strategy to overcome the weak points of a random copolymer system. Block copolymers composed of hydrophilic and hydrophobic segments are expected to form ion transport channels due to hydrophilic/hydrophobic phase separated structures and show improved proton conductivity. Poly(phenlyquinoxalines) are a family of aromatic condensation polymers known their outstanding thermal and chemical stability. Based on this polymer class new sulfonated block copolyphenylchinoxalines with hydrophilic and hydrophobic segments have been developed. The block copolymers were synthesized via polycondensation reactions between 3,3`-4,4`tetraaminodiphenylether and two different tetracetones, followed by sulfonation using a mixture of concentrated sulfuric acid. and oleum (4:1).High molecular-weight polymers over 20 000 in number average molecular weight were easily obtained and gave tough and flexible membranes by solvent casting. The properties of their membranes, such as proton conductivity, water uptake, oxidation and dimensional stability were investigated und presented.