Synthesis and Polyelectrolyte Functionalization of Hollow Fiber Membranes Formed by Solvent Transfer Induced Phase Separation

Abstract

Ultrafiltration membranes are important porous materials to produce freshwater in an increasingly water-scarce world. A recent approach to generate porous membranes is solvent transfer induced phase separation (STrIPS). During STrIPS, the interplay of liquid−liquid phase separation and nanoparticle self-assembly results in hollow fibers with small surface pores, ideal structures for applications as filtration membranes. However, the underlying mechanisms of the membrane formation are still poorly understood, limiting the control over structure and properties. To address this knowledge gap, we study the nonequilibrium dynamics of hollow fiber structure evolution. Confocal microscopy reveals the distribution of nanoparticles and monomers during STrIPS. Diffusion simulations are combined with measurements of the interfacial elasticity to investigate the effect of the solvent concentration on nanoparticle stabilization. Furthermore, we demonstrate the separation performance of the membrane during ultrafiltration. To this end, polyelectrolyte multilayers are deposited on the membrane, leading to tunable pores that enable the removal of dextran molecules of different molecular weights (>360 kDa, >60 kDa, >18 kDa) from a feed water stream. The resulting understanding of STrIPS and the simplicity of the synthesis process open avenues to design novel membranes for advanced separation applications.

Roll‐to‐Roll Fabrication of Bijels via Solvent Transfer Induced Phase Separation (R2R‐STrIPS)

“…[5,33,34] As a result, the CTA + -modified SNPs stabilize the phase separating BDA/water domains via interfacial jamming (Figure 1C-ii). [14] STrIPS results in films composed of particle stabilized bicontinuous emulsion gels (bijels) with toothpaste-like consistency.…”

“…[7] STrIPS yields kinetically arrested bicontinuous oil/water networks, [8] a structure defined as a bicontinuous interfacially jammed emulsion gel (bijel). [9][10][11][12] STrIPS-bijels have been employed as ultrafiltration membranes with antifouling surface coatings, [13,14] catalytic membranes, [15] liquid-liquid extraction devices [8] and as organic solvent-resistant porous materials. [16,17] Moreover, their bicontinuous structure has been shown to provide high solar reflectivity for passive cooling coatings.…”

“…Currently, STrIPS-bijels can be continuously made at rates of milliliters per hour via microfluidics. [14,15,19,20] Additionally, potentially scalable batch fabrication methods have been employed to generate bijels via other methods than STrIPS. [18,[21][22][23][24] As opposed to bijel production, the mass production of flat-sheet NIPS membranes can be readily accomplished via doctor blade-, roll-, and slot die-coating.…”

Biomimetic mussel technology for membrane material modification: Adhesion mechanism and design strategy

“…Thus, a metal-polyphenol coordination network is derived. 89,90 As an alternative derivative of PDA, polyphenols also possess the ability to chelate and coordinate with metal particles. Zhao et al 91 modified PVDF membranes by in situ introducing metal ions (Ti-IV) and polyphenols F I G U R E 6 (A) A novel thin film nanocomposite membrane obtained by modifying PA layer with COFs.…”

“…Many studies have found that polyphenols such as gallic acid and tannic acid (TA) have a catechin structure similar to dopamine. Thus, a metal‐polyphenol coordination network is derived 89,90 …”