Introducing angled arene units or short flexible alkyl segments into rigid aromatic hetero-atom-free polymer backbones is an efficient strategy to improve the performance of anion exchange membranes (AEM)s. So far, only very few monomers have been presented that increase backbone flexibility in polymers prepared by polyhydroxyalkylations, often with limited reactivity and polymerizability. Here, we present the synthesis of a highly reactive monomer [m-di(biphenyl)ethane, mD] containing two angled biphenyl units bridged by ethane link using a straightforward noble-catalyst-free reductive homocoupling reaction. A series of copolymers were prepared by polyhydroxyalkylation of p-terphenyl, N-methylpiperidone, and different concentrations of mD. Small angle X-ray scattering analysis of the AEMs indicated enhanced ionic clustering withincreasing mD content and backbone flexibility. Moreover, water and KOH (aq.) uptake, hydroxide conductivity and alkaline stability increased with the mD content. The hydroxide conductivity of an AEM containing 25% mD units reached 187 mS cm-1 at 80 °C in water, and an AEM with 50% mD units exhibited a conductivity of 53 mS cm-1 in 2 M KOH (aq.) solution. Using only simple nickel foam electrodes, the latter AEM reached a current density of >400 mA cm-2 at 2.5 V without any cell optimization. In summary, this work demonstrates a convenient synthetic strategy to incorporate flexible units in rigid aromatic polymers prepared by polyhydroxyalkylation, offering improved membrane properties and valuable insights into the design and optimization of advanced AEM materials.