Alumina Priming-Mediated Enhanced Binding of Diethylzinc with Carbonyl Groups in Poly(Methyl Methacrylate) during Vapor-Phase Infiltration

Vapor-phase infiltration (VPI) of inorganic materials in polymers is increasingly becoming popular for synthesizing various functional hybrid materials. While AlO _<i>x</i> infiltration using trimethylaluminum (TMA) has been extensively studied, the mechanism of diethylzinc (DEZ)-based ZnO _<i>x</i> infiltration, especially one that is initiated by AlO _<i>x</i> priming, has not received much attention because highly reactive hydroxyl groups generated by AlO _<i>x</i> -priming are expected to dominate the initial binding of DEZ, thus enabling the overall ZnO _<i>x</i> VPI. Here, we interrogate the ZnO _<i>x</i> infiltration mechanism in AlO _<i>x</i> -primed poly-(methyl methacrylate) (PMMA) in comparison to the control AlO _<i>x</i> -only infiltration by utilizing a suite of complementary characterizations, including quartz crystal microbalance mass gain measurement, transmission electron microscopy, infrared reflection-absorption spectroscopy (IRRAS), and synchrotron X-ray absorption spectroscopy (XAS). The multivalent TMA precursor and associated hyperbranched AlO _<i>x</i> network can quickly saturate the AlO _<i>x</i> infiltration by clogging the polymer-free volume near the top. On the contrary, the ZnO _<i>x</i> infiltration using divalent DEZ precursor, once activated via AlO _<i>x</i> -priming, can lead to accelerated ZnO _<i>x</i> infiltration. With the help of IRRAS, XAS, and density functional theory (DFT) simulations, we uncover that the AlO _<i>x</i> -priming enhances the reactivity of neighboring carbonyl groups toward DEZ and opens up simultaneous reaction pathways, leading to accelerated high-fidelity infiltration of ZnO _<i>x</i> .