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Titanium oxide (TiO2) coated polyimide has broad application prospects under extreme conditions. In order to obtain a high-quality ultra-thin TiO2 coating on polyimide by atomic layer deposition (ALD), the polyimide was activated by in situ oxygen plasma. It was found that a large number of polar oxygen functional groups, such as carboxyl, were generated on the surface of the activated polyimide, which can significantly promote the preparation of TiO2 coating by ALD. The nucleation and growth of TiO2 were studied by x-ray photoelectron spectroscopy monitoring and scanning electron microscopy observation. On the polyimide activated by oxygen plasma, the size of TiO2 nuclei decreased and the quantity of TiO2 nuclei increased, resulting in the growth of a highly uniform and dense TiO2 coating. This coating exhibited excellent resistance to atomic oxygen. When exposed to 3.5 × 1021 atom cm−2 atomic oxygen flux, the erosion yield of the polyimide coated with 100 ALD cycles of TiO2 was as low as 3.0 × 10−25 cm3/atom, which is one order less than that of the standard POLYIMIDE-ref Kapton® film. [ABSTRACT FROM AUTHOR]

Polymeric materials, including polyethylene terephthalate (PET), are widely used in various fields because of their beneficial properties. Functional films are deposited on these materials through different approaches, such as plasma-enhanced atomic layer deposition (PEALD), to enhance their performance and prolong their life span. However, the inert and thermally fragile nature of most polymers hinders deposition. We developed a strategy for the PEALD of nanoscale Al2O3 films on PET substrates. First, a PET substrate is subjected to alkali treatment, which gives it basic hydrophilicity for the subsequent dopamine modification. After 24 h of dopamine deposition, the substrate shows adequate active sites (phenolic hydroxyl groups), which can chemisorb large amounts of precursor during the initial deposition. The island growth mode was observed during the PEALD processes. We analyzed the detailed chemical components of Al2O3 on alkali-treated PET and dopamine-modified PET. After 100 cycles of deposition, the Al2O3 films on both samples contained much hydrogen. Benefitting from the more active sites, we observed more continuous Al2O3 film on dopamine-modified PET, which exhibited excellent water vapor blocking performance. Our findings suggest that dopamine could act as a ‘bridge’ between polymers and PEALD functional films. [ABSTRACT FROM AUTHOR]

[Display omitted] • Our study demonstrates a novel strategy for the ultrathin ALD-Al 2 O 3 film depositing onto polyethylene terephthalate via polydopamine modification (PDA@PET). • Earlier nucleation, more consecutive growth, and more conformal film are observed during the ALD onto PDA@PET. • The presence of the PDA layer narrowed the region of TMA infiltration into the PET, resulting in the formation of a conformal film on the surface. • An ultrathin ALD-Al 2 O 3 film on PDA@PET shows excellent water vapor blocking performance. Atomic layer deposition (ALD) has drawn considerable attention recently for depositing functional films on polymers. However, most polymers are inert and thermally fragile, thus posing many challenges during deposition. This study presents a novel strategy for ALD of an ultrathin Al 2 O 3 film on alkali-treated polyethylene terephthalate (PET) via polydopamine (PDA) modification. The tightly adherent PDA layer exhibited numerous robust active sites (phenolic hydroxyl groups), which are highly desirable for precursor chemisorption during ALD. The modification process was systematically characterized. The PET substrate showed many active sites and a smooth surface after 24 h of PDA deposition. The island growth mode was found during the ALD of an Al 2 O 3 film on the samples. The PDA layer absorbed a large quantity of the precursor (trimethylaluminum [TMA]) during the initial deposition, contributing to the early nucleation and continuous growth of the Al 2 O 3 film. In addition, the presence of the PDA layer narrowed the region of TMA infiltration into the PET, resulting in the formation of a conformal film on the surface. Transmission electron microscopy indicated that an Al 2 O 3 film with a thickness of about 10 nm was formed on the PDA-modified PET substrate after 100 ALD cycles, and exhibited excellent water vapor blocking characteristics. These findings suggest that the added PDA layer has tremendous potential to act as a bonding layer between polymers and ALD functional films. [ABSTRACT FROM AUTHOR]