Vapor phase infiltration (VPI) has emerged as a scalable process that can transform polymer products into organic-inorganic hybrid materials via the exposure of polymer products to vapor phase metal-organic precursors, which modifies the materials’ chemical stability, hydrophilicity, conductivity, and mechanical properties. As a result, VPI has been applied in a wide range of fields such as polymer membranes for chemical separations and catalysis. However, the fundamental transport behaviors of VPI are not well understood. To date, most explorations rely on Fickian kinetics for simplicity, which fails to capture the physical phenomena of VPI due to the complex convolution of precursor diffusion and the reaction between precursor and polymer matrix. In this work, we will present a reaction-diffusion model that provides critical insight into how the presence of reactions will change the transport behavior of metal-organic precursors through the polymer. The model is shown to both fit and more critically, predict experimental processes with a high degree of confidence. Specifically, the infiltration process of trimethylaluminum (TMA) into poly(methyl methacrylate) (PMMA) at 130 <sup>o</sup>C is studied, a temperature where both diffusion and reaction occur. Additionally, a method of nondimensionalization is employed to create domain maps representative of the wide range of behaviors the reaction-diffusion model for VPI can capture to provide a broad overview of how different parameters influence VPI behavior.

Reaction diffusion transport model to predict precursor uptake and spatial distribution in vapor phase infiltration processes

ACS Fall 2021

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