Dual pH-responsive smart gating membranes

A novel dual pH-responsive smart gating membrane is proposed for the first time by skillfully blending poly(N,N′-dimethylamino-2-ethyl methacrylate) (PDMAEMA) microgels into poly(ether sulfone) membrane as functional gates via liquid-induced phase separation method. The as-prepared membrane exhibits dual pH-responsive characteristics, i.e., this novel membrane is featured with both positively pH-responsive characteristics in acidic environment and negatively pH-responsive characteristics in basic environment. The mechanism of the positively pH-responsive performance is attributed to the pH-responsive volume change of PDMAEMA microgels embedded in the membrane, while that of the negatively pH-responsive performance is originated from the pH-responsive hydrophobicity and stiffness of the microgels. As a result, the permeability of this novel membrane is increased at first and then decreased with increasing the environmental pH value. The dual pH-responsive property of the prepared membrane is reversible and repeatable. The dual pH-responsive membrane proposed in this study provides a novel gating mode for design and development of pH-responsive smart membranes, which is highly potential for myriad applications, such as sewage treatments, sensors, controlled release of drugs and so on.