Elucidating the Kinetics and Thermodynamics of Organic Vapor Phase Infiltration and Molecular Layer Deposition for...

Vapor phase chemical synthesis techniques, such as atomic layer deposition (ALD) and vapor phase infiltration (VPI), enable molecular-level tailoring of polymeric materials through deposition or incorporation of inorganic components. However, benefits are often paired with compromised mechanical stability and organic-inorganic bonds that are prone to degradation via hydrolysis. To address these limitations, we investigate all-organic VPI and molecular layer deposition (MLD) chemistries as a strategy for enhancing polymer properties. We examine the reaction-diffusion kinetics and thermodynamic behavior of three aromatic step-growth polymerization reactions: polyamide (isophthaloyl chloride + m-phenylenediamine, MPD), polyurea (1,4-phenylene diisocyanate + MPD), and polyimine (terephthalaldehyde + MPD). Their material growth occurs via MLD at the surfaces of nonabsorbing silicon and zirconia. Organic VPI occurs within the bulk of nucleophile-rich polyvinyl alcohol (PVA), but not through physical entrapment in unreactive polystyrene and poly-(methyl methacrylate). Using a reaction-diffusion model, we quantify diffusion-limited polyamide and reaction-limited polyurea nucleation behavior in PVA, identifying key parameters: diffusivity, reaction rate, and Damköhler number. Unlike inorganic alumina treatment, organic modification enhances dissolution-resistance in PVA, preserving polymer integrity and resisting hydrolysis even in harsh pH 13 solutions. This study demonstrates the potential of all-organic material deposition for synthesizing novel polymers with improved durability and solvent resilience.