Because of its high conductivity and intrinsic stability, poly(3,4-ethylenedioxythiophene (PEDOT) has gained great attention both in academic research and industry over the years. In this study, we used the oxidative molecular layer deposition (oMLD) technique to deposit PEDOT from 3,4-ethylenedioxythiophene (EDOT) and a new inorganic oxidizing agent, rhenium pentachloride (ReCl 5 ). We extensively characterized the properties of the films by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), Raman, and conductivity measurements. The oMLD of polymers is based on the sequential adsorption of the monomer and its oxidation-induced polymerization. However, oMLD has been scarcely used because of the challenge of finding a suitable combination of volatile, reactive, and stable organic monomers applicable at high temperatures. ReCl 5 showed promising properties in oMLD because it has high thermal stability and high oxidizing ability for EDOT. PEDOT films were deposited at temperatures of 125−200 °C. EDS and XPS measurements showed that the as-deposited films contained residues of rhenium and chlorine, which could be removed by rinsing the films with deionized water. The polymer films were transparent in the visible region and showed relatively high electrical conductivities within the 2−2000 S cm −1 range.

In this paper, the deposition of pyrrone thin film materials by molecular layer deposition (MLD) is reported for the first time using pyromellitic dianhydride (PMDA) and 3,3'‐diaminobenzidine (DAB) as monomers, and ozone as a promoting precursor. Besides ozone, the effect of water, hydrogen peroxide, and oxygen is also tested to promote the growth of MLD thin films. Ozone as a strong oxidant is the best reactant in this process. Two precursor pulsing sequences are tested and both result in pyrrone films. With the DAB+O3+PMDA sequence, growth per cycle (GPC) of 1.2 Å is obtained at 250–300 °C, whereas with the DAB+PMDA+O3 sequence, GPC of 1.5 Å is obtained. When only DAB and O3 are used, indamine films with GPC of 1.0 Å are obtained. The films are characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy. Chemical, thermal, and electrical properties of the films are also investigated. The films are stable in acidic and basic solutions and organic solvents, and they withstand 300 °C when annealed in air.

aliphatic or aromatic derivatives as monomers for optimizing application specific properties for bioactive materials and fuel cell membranes, for example. [17,18] In recent years, with the developments of using insulating polymer materials in electronic devices, needs for high-thermalresistance polymer dielectrics have been increasingly emphasized in order to ensure high reliability of devices operating at high temperatures. [19] While conventional polyethylene and polypropylene possess intrinsically excellent insulating properties, [20] they are facing great challenges in advanced electrical devices due to their limited service temperatures below 105 °C and increased leakage currents at elevated temperatures. [2,20,21] Another prevalent area for PBI lies in membrane applications such as H 2 separation membranes, fuel cells, and redox battery membranes. High intrinsic H 2 selectivity over larger gas molecules, such as CO 2 , N 2 , and CH 4 , was demonstrated with PBI film membranes prepared using flat and hollow polyamide P84 fibers as a support material. [8] PBI has gained great interest also as a membrane material in vanadium redox flow batteries where ion-selectivity for vanadium was obtained with a thin layer of PBI polymer. [22] Polybenzimidazoles and their more complex derivatives are often classified as expensive specialty plastics due to their outstanding properties but also difficulties in manufacturing. PBI plastics are known as the thermally most stable thermoplastics with a glass transition temperature (T g ) higher than 400 °C. [11] In a previous study by Iqbal et al. [19] PBI exhibited excellent thermal stability up to a temperature of 500 °C with a total weight loss of only 15%. The stability of PBI polymers drives from the high number of aromatic rings incorporated in the polymer chain. Aromatic rings are efficiently absorbing both thermal and radiation energy and aid in redistributing the excitation energy throughout the material. [18,19] Conventional PBI polymers are usually prepared via hightemperature polycondensation reactions in either solution or melt to achieve high degree of cyclization. [23][24][25] PBIs are typically synthesized from aromatic tetraamines (bis-o-diamines) and dicarboxylates (acids, esters, or amides) [26] (Scheme 2).PBI thin films are scarcely reported. Previous depositions were carried out either by a casting solution method from formic acid and dimethylsulfoxide (DMSO) solutions or dip-coating and blade-casting methods. [23] The deposition of polybenzimidazole (PBI)-like thin films by molecular layer deposition is reported here for the first time using isophthalic acid (IPA) and 3,3′-diaminobenzidine (DAB) as monomers and trimethylaluminum (TMA) as a linker precursor. Two precursor pulsing sequences are tested, the ABCB (TMA + IPA + DAB + IPA) and ABC (TMA + IPA + DAB) type MLD processes result in different types of PBI-like films. With the ABCB sequence thin film growth per cycle (GPC) of 6.0 Å is obtained at 225-280 °C, whereas GPC of 7.0 Å is obtained with the ABC s...