Star polymers as functional building blocks for novel nanofiltration membranes

Star polymers as functional building blocks for novel nanofiltration membranes




Thin film composite membranes (TFC) play an important role in many separation processes, e.g.  water desalination or gas separation. Due to this versatile applicability, very good separation performance and relatively low costs and energy input, interest in TFC membranes with separation properties specifically tailored to certain separation processes is growing. In order to obtain such membranes with high permeability, permselectivity and fouling resistance, already established membrane systems can be combined with novel building blocks. A class of promising building blocks are star polymers. These have a compact, globular structure with a high density of functional groups [1].

In this work star polymers are synthesized using cyclodextrins as core and by controlled atom transfer radical polymerization (ATRP). Depending on the number of hydroxyl groups on the cyclodextrin used as initiator sites and on ATRP conditions, the chain density in and the overall size of the star polymers can be tailored independently. First types of such building blocks contain carboxylic acid or amino groups. Subsequently, the star polymers are embedded in TFC polyamide membranes by interfacial polymerization. Polyamide membranes are commonly used in nanofiltration or reverse osmosis processes. By functionalizing them with star polymers, the membranes’ permeability is expected to increase significantly while the typical selectivity is expected to change, because the incorporated building blocks act as transport domains in the ultrathin separation layer. Of particular interest are membranes which contain building blocks of two or more different types.


  1. J. M. Ren, T. G. McKenzie et al., Chemical Reviews 2016, 116, 6743

Vanessa Schnecke