Novel polymeric additives in the preparation and modification of polymeric membranes: A comprehensive review

One of the basic challenges in polymeric membrane fabrication is the control of pore size and the porosity of the membranes. In this review paper, the role of polymeric additives is overviewed in membrane fabrication processes, such as the formation of pores in membranes, increasing permeability, hydrophilicity and even the creation of a desirable property such as antifouling and antibacterial properties. The polymeric additives could dissolve in water during the phase inversion process (a pore forming agent) or remain in the membrane matrix (hydrophilic and antifouling agent) or could have both roles. The additives could also act as proton exchanger and gas transport facilitating agents. This review concentrates on the introduction of new polymeric additives. In the blended membranes, the miscibility of chosen polymeric additives at the molecular levels make it a challenge to use the modification method. Molecular interactions between polymers such as hydrogen bonding and charge transfer play the main roles of the quality of blending. Different methods of polymer/co-polymer addition to the polymeric matrix of membranes are investigated to identify the best polymeric additives in various types of polymeric membranes including: pervaporation, contactor membrane, distillation membrane, etc. Moreover, the mixability of the additive polymer with the matrix polymer solution and the effectiveness of some functional additives are described in this review.