Embedding Dopamine Nanoaggregates Into Poly(dimethylsiloxane) Membrane to Confer Controlled Interactions and Free Volume for Enhanced Separation Performance

Poly(dimethylsiloxane) (PDMS) has been demonstrated as one of the most-widely utilized membrane materials. However, pure PDMS membranes often undergo severe swelling and exhibit low permselectivity due to its too flexible Si-O backbone.

In this study, a facile and generic approach for fabricating high-performance hybrid PDMS membranes by incorporating versatile dopamine and dopamine/M nanoaggregates was described. These nanoaggregates will play at least the following three roles within the membrane: (1) intervening the polymer chain packing, tuning the inter-chain spacing and endowing the membrane with favorable free volume property. (2) forming non-covalent interactions with PDMS, which can reinforce chain rigidity, optimize interfacial free volume and elevate cohesive energy of the membrane. (3) acting as facilitated transporters which can specifically and reversibly react with the target penetrant via π-complexation interaction and thus improve the membrane permeation flux, in particular, permselectivity.

When the as-prepared hybrid PDMS membranes were utilized for model gasoline separation, their permeation fluxes and enrichment factors were increased simultaneously, exceeding the upper bound curve of PDMS control membrane. When the dopamine/Cu content reached 5.0 wt%, the membrane acquired permeation flux of 7.42 kg∙m^-2∙h^-1 with enrichment factor of 4.81 under 30 ^oC and 40 L/h of feed solution. Meanwhile, the swelling-resistance property and thermal stability of the membranes were remarkably enhanced thanks to the elevated cohesive energy and the chain extension effect.

Since a broad range of bioadhesive molecules can spontaneously polymerize and self-assemble into nanoaggregates, and these nanoaggregates can form the multiple non-specific interactions with many kinds of polymers and the coordination interaction with many kinds of transition metals, our approach may be applicable for the rational design and fabrication of a variety of hybrid membranes.