(694a) Facile Fabrication of ZnO-Polymer Hybrid Thin Films Via Vapor Phase Infiltration

Vapor phase infiltration (VPI) is an emerging method for synthesizing organic-inorganic hybrid thin films. In a typical VPI process, metalorganic precursor vapor diffuses and reacts into polymer matrixes to form hybrid materials. The simple vapor process enables modification of the mechanical, optical and electronic properties of the matrix polymer, and can be used in pattern transfer from directed self-assembly of block copolymers. The incorporation of ZnO nanoparticles in polymer matrixes could obtain tunable dielectric and piezoelectric properties, and enable applications in EMI shielding, sensing, and energy storage. Unlike trimethylaluminum (TMA), however, very few processes have been reported for the infiltration of diethylzinc (DEZ) into polymers to form ZnO-incorporated hybrid materials, because the large molecular size of DEZ hinders the diffusion while the weak Lewis acidity of Zn affects the reactivity to form adducts with the Lewis basic groups in the polymer structure. In this work, we explored a seeding process using VPI Al₂O₃ for the subsequent diffuse and reaction of DEZ in a variety of polymers. With Al-OH moieties pre-formed in the polymer, we found that VPI ZnO can fully infiltrate spun-coated poly(methyl methacrylate) (PMMA) thin films (ca. 80 nm thickness) and achieve substantial Zn loading in the PMMA films. We further compared the VPI ZnO process in PMMA, poly(butylene terephthalate) (PBT) and cellulose acetate (CA) to study the roles of the functional groups (e.g. ester and hydroxyl groups) and the crystallinity of the polymer matrixes. Additionally, we evaluated the mechanical and dielectric properties of these VPI-fabricated hybrid materials. Our results are expected to provide new insights for the VPI ZnO process and guide future design of vapor-phase approaches for organic-inorganic hybrid films.