Phosphonic acid-containing homo-, AB and BAB block copolymers via ATRP designed for fuel cell applications

The synthesis of various block copolymers containing phosphonic acid moieties is described. Poly(styrene)/PDEVBP AB block copolymers were obtained by atom transfer radical polymerization (ATRP) of diethyl p-vinylbenzyl phosphonate (PDEVBP). Subsequently, BAB block copolymers with tailored architecture composed of the phosphonated monomer and poly(ether ether ketone) were obtained by a combination of polycondensation chemistry and ATRP. The quantitative deprotection of the ethyl phosphonates led to the corresponding free phosphonic acids, which can be applied as polymer electrolyte membranes for fuel cells. In addition, all materials showed high thermal stability. The proton conductivity properties of the ionomers were investigated. The phosphonic acid-containing (co)polymers exhibited a linear increase of the conductivity with the temperature with a maximum value of 4.5 × 10−4 S/cm in anhydrous conditions.