Vapor phase infiltration (VPI) is a post-polymerization modification technique for embedding inorganic clusters within polymer networks to create organic-inorganic hybrid materials with properties unique from the parent polymer. Recently, our research team has used VPI to synthesize hybrid membranes with consistent nanofiltration performance in a variety of organic solvents that would otherwise swell or dissolve the parent polymer membrane. This talk will discuss how variations in VPI process pressures and precursor chemistries can be used to vary inorganic loading in these hybrid membranes and the impacts on chemical separation performance. First, we will report on how variations in the partial pressure of the trimethylaluminum (TMA) precursor alter inorganic loading. We find that inorganic loadings as low as 6.7% can be achieved when infiltrating at 0.2 Torr and as high as 13.2% can be achieved when infiltrating at 1.1 Torr. Inorganic loadings were verified using TGA, XPS, and Raman spectroscopy. Secondly, we examine the differences in inorganic loading for three different precursor chemistries at a constant VPI process pressure of 0.2 Torr: (1) TMA, (2) diethylzinc (DEZ), and (3) titanium tetrachloride (TiCl<sub>4</sub>). Mass loadings for each of these chemistries appear to scale almost linearly with density functional theory calculations of their binding chemistries to the PIM-1 polymer. This correlation provides new insight for future selection and design of precursors for infiltration of polymer membranes. Finally, we will discuss how these difference in inorganic loading affect membrane swelling, dissolution, permeation, and separation performance.

Effects of vapor pressure and chemistry on inorganic loading of PIM-1 membranes modified via vapor phase infiltration for chemical separations

ACS Fall 2021

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