Effects of trimethylaluminum vapor pressure and exposure time on inorganic loading in vapor phase infiltrated PIM-1 polymer membranes

Abstract

Vapor phase infiltration (VPI) is a post-polymerization modification method for infusing inorganic clusters into a polymer to create organic-inorganic hybrid materials with properties that are unique from the parent polymer. The properties of these hybrid materials can vary with the amount of VPI generated inorganic loading. However, the relationship between VPI processing conditions and inorganic loading is still not fully understood. In this paper, the effects of VPI dose pressure and exposure time on inorganic loading are explored using the technologically relevant membrane material known as “polymer of intrinsic microporosity 1” (PIM-1). At sufficiently low dose pressures and infiltration times (i.e., before saturation), inorganic loading can be controlled with both vapor pressure and exposure time. However, inorganic loading appears to saturate for this system when the polymer's functional groups become fully populated with bound VPI precursors. These experimental results can be understood with the use of a recently developed reaction-diffusion model for VPI. Critical to applying this model to these post-deposition measurements is re-normalizing the mass loading to the total number of functional groups in the polymer.