Vapor Phase Infiltration of Metal Oxides into Nanoporous Polymers for Organic Solvent Separation Membranes

Abstract

Membrane-based organic solvent separations promise a low-energy alternative to traditional thermal separations but require materials that operate reliably in chemically aggressive environments. While inorganic membranes can withstand demanding conditions, they are costly and difficult to scale. Polymeric membranes, such as polymer of intrinsic microporosity 1 (PIM-1), are easily manufactured into forms consistent with large-scale separations (e.g., hollow fibers) but perform poorly in aggressive solvents. Here, a new postfabrication membrane modification technique, vapor phase infiltration (VPI), is reported that infuses PIM-1 with inorganic constituents to improve stability while maintaining the polymer’s macroscale form and nanoporous internal structure. The atomic-scale metal oxide networks within these hybrid membranes protect PIM-1 from swelling or dissolving in solvents. This stability translates to improved separation performance in a variety of solvents, including solvents capable of dissolving PIM-1. The infiltrated inorganic phase also appears to give new control over solute sorption in organic solvent nanofiltration (OSN). These hybrid membranes further show promising performance for organic solvent reverse osmosis (OSRO) separations in challenging solvents, even at small-molecular-weight differentials (14 Da). Because the VPI process can be integrated with state-of-the-art membrane modules, this treatment could be readily adopted into the large-scale manufacturing of advanced membranes.

Preserving nanoscale features in polymers during laser induced graphene formation using sequential infiltration synthesis

“…The method of combining SIS of organometallic precursors into polymers with LIG formation described in this paper can be generalized to other applications where maintaining micro and nano-sized features of polymers at temperatures well above their T g is desired. An even broader advantage of this approach is the improved mechanical and chemical properties that are observed at these high temperatures, without the need to change the chemistry of the underlying polymer 28 . Other modification approaches that could potentially be used, such as crosslinking of the polymer, would alter the polymer chemistry, potentially altering the material's LIG forming properties.…”

“…Similar to atomic layer deposition (ALD), SIS involves the sequential exposure of a material to alternating vapors of a reactive organometallic precursor and a counter reactant 24,25 . While ALD is performed on a non-porous substrate to grow inorganic films 26 , SIS is performed on polymers, where the diffusion of reactants into the polymer can change its chemical and mechanical properties, increasing its tensile strength 27 , changing its permeability to certain molecules 28 , improving its conductivity 29 , or allowing it to maintain its structure during annealing [30][31][32][33] . ALD, and similar techniques like SIS, have been widely and safely used for decades, both in industry and academic research 34 .…”

Vapor phase infiltration of zinc oxide into thin films of cis-polyisoprene rubber

“…Note that the glass transition temperature for this polymer is around À64 1C. 18 Vapor phase infiltration (VPI) of the polymer films was performed in a custom-built system described earlier, 15 and was controlled via a tree-based control software. 19 The chamber was operated at a temperature of 60, 80, or 100 1C.…”

“…The ability to increase chemical stability of polymers in solvents by VPI has been reported for different systems. 8,15 In a recent study by McGuinness et al, 8 the stability of AlO x -poly(methyl methacrylate) hybrid films was tested in various solvents. The authors found that the infiltration temperature controlled the physicochemical structure of the final hybrid material and its resultant chemical dissolution performance.…”

“…11,12 For example, VPI has been used to increase the toughness of spider silk, 13 increase the electrical conductivity of semiconducting polymers, 14 and increase the solvent stability and separation performance of membranes. 15 A recent investigation examined the use of vapor phase infiltration to incorporate inorganic materials into block co-polymers containing a rubber (elastomeric) block. In this recent study, VPI with diethyl zinc and water was used to infiltrate ZnO into epoxidized and unepoxidized polystyrene-block-poly(1,4-isoprene) copolymers (PS-b-PI).…”