Insight on the Sequential Vapor Infiltration Mechanisms of Trimethylaluminum with Poly(methyl methacrylate), Poly(vinylpyrrolidone), and Poly(acrylic acid)

The sequential vapor infiltration (SVI) method, based on atomic layer deposition chemistry, allows the creation of a polymer-inorganic hybrid material through the diffusion of metal-organic vapor reagents into a polymer substrate. This study investigates the reactivity of the ester, amide, and carboxylic acid functional groups of poly(methyl methacrylate) (PMMA), poly(vinylpyrrolidone) (PVP), and poly(acrylic acid) (PAA), respectively, in the presence of trimethylaluminum (TMA) vapor. This work explores the possible reaction mechanisms of these functional groups through in situ Fourier transform infrared spectroscopy and ab initio quantum chemical analysis. At temperatures of <= 100 degrees C, TMA physisorbs to the carbonyl groups of PMMA. As the temperature is increased, TMA forms a covalent bond with PMMA. TMA physisorbs to PVP and then partially desorbs in the presence of water for all studied temperatures of <= 150 degrees C. PAA readily reacts with TMA to form a covalent bond with the carbonyl group at 60 degrees C. This increased reactivity is attributed to the acidic proton in the carboxylic acid moiety based on TMA's reactivity with hydroxyl-terminated surfaces and ab initio calculations. At temperatures of >= 100 degrees C, TMA catalyzes anhydride formation in PAA. These insights will help with the prediction of chemical interactions in SVI processes for the development of organic-inorganic hybrid materials.