Self-Assembled Polymer Nanostructures for Liquid Filtration Membranes: A Review

Membrane separations are a crucial technology in water desalination, wastewater treatment, bio-processing, and the food and beverage industries. Most commercial membranes available today for liquid filtration were developed using trial-and-error methods and are based on a handful of materials. Recent efforts use polymer self-assembly at the nanometer scale to develop membranes with improved permeability, selectivity, and fouling resistance. For example, block copolymer self-assembly into cylindrical or gyroid microphases has been used for membranes with very high flux and tight selectivity and can be integrated into large scale membrane manufacture. Graft copolymer microphase separation has been used to form membranes with similar to 1 nm size cut-offs, while exceptional selectivity has been achieved by desalination membranes obtained from polymerizable liquid crystals. Surface segregation of amphiphilic copolymers has been also used to manufacture fouling resistant membranes in a single step. All these examples represent a new approach to the development of novel membranes, i.e., the design of materials with tailored surface properties and nanostructures.