Polymermembraner

Polymermembraner is a term used to describe polymer-based membranes designed for selective transport in separation processes. These membranes typically consist of a porous substrate onto which a thin, selective polymer film is formed. The selective layer governs which molecules pass through and at what rate, while the substrate provides mechanical strength and chemical resistance.

Materials and structures: common polymers include polyimides, polysulfones, polyethersulfones, polyvinylidene fluoride, cellulose derivatives, and polyamides. Membranes can be dense, with permeation across a nonporous film, or porous, where transport occurs through pores. Thin-film composite membranes stack a dense active layer on a porous support.

Fabrication and tuning: phase inversion and solvent casting create porous supports; interfacial polymerization forms thin-film composite membranes; electrospinning yields nonwoven mats. Surface modification (grafting, plasma or UV treatments) improves fouling resistance and chemical stability. Mixed-matrix membranes incorporate inorganic fillers to enhance selectivity and stability.

Performance and metrics: performance is described by permeability and selectivity. For gases, permeabilities are measured in Barrer and selectivity as the ratio of permeabilities; for liquids, flux and rejection/retention metrics are used. A typical consideration is the trade-off between permeability and selectivity, often discussed in the context of the Robeson upper bound for gas separations. Stability and aging, including plasticization and chemical compatibility, are important in many applications.

Applications: polymermembraner materials are used in water treatment and desalination, gas separations (such as CO2/CH4 and O2/N2), pervaporation, and various filtration processes in chemical and biomedical industries.

Challenges and outlook: ongoing research targets higher performance, fouling resistance, and longer-term durability, with approaches like crosslinking, novel monomers, and advanced mixed-matrix designs.