Deposition of Ion-Conductive Membranes from Ionic Liquids via Initiated Chemical Vapor Deposition

In this study, liquid droplets of 1-allyl-3-methylimidazolium dicyanamide have been processed by initiated chemical vapor deposition (iCVD) with a cross-linked polymer film consisting of (hydroxyethyl)methacrylate and ethylene glycol dimethacrylate to develop free-standing, ion-conductive membranes. We found that the obtained films are solids and have a conductivity of up to 18 ± 6 mS/cm, associated with the negatively charged counterion, indicating no loss of conductivity, compared to the ionic liquid in the liquid state. The membranes were conductive within a large process window and in air, thanks to the fact that the iCVD process does not affect the mobility of the anion in the ionic liquid. Furthermore, we demonstrate that varying the deposition conditions can influence the homogeneity and conductivity of the resulting membranes. The promising results of this study represent an important stepping stone on the way to novel ion-conductive membranes

Simple method for the quantitative analysis of thin copolymer films on substrates by infrared spectroscopy using direct calibration

The chemical composition of a copolymer drives many important material properties and quantification in terms of comonomer volume fraction is thus of practical relevance for many studies. Infrared spectroscopy is one of the most common techniques for compositional analysis but it usually relies on manual evaluation of baselines and peak heights, which can be rather inaccurate and become a laborious task when having multiple spectra to evaluate. On the contrary, Maxwell's theory of electrodynamics can be used to calculate the complex index of refraction from measured spectra promising a more accurate quantification. Since this procedure is rather involved, we propose a simple in-house developed IR-quantification routine to automatically evaluate the comonomer volume fractions of thin copolymer films by using the Bouguer-Lambert-Beer approximation after correcting the baseline of all absorbance spectra automatically. This method was experimentally evaluated on over 40 thin polymeric coatings synthesized by initiated chemical vapor deposition on silicon substrates. The samples comprised a wide range of different compositions and were synthesized from four different monomers, with single films consisting of up to three components. All data obtained by our routine was compared with data from spectroscopic ellipsometry and with X-ray photoelectron spectroscopy data of selected samples. The comparisons show that the IR-quantification routine reliably evaluated the polymer composition even when the involved comonomers exhibited similar chemistry, as it is the case for methacrylic acid cross-linked with ethylene glycol dimethacrylate

Tuning of material properties of ZnO thin films grown by plasma-enhanced atomic layer deposition at room temperature

The ability to grow inorganic thin films with highly controllable structural and optical properties at low substrate temperature enables the manufacturing of functional devices on thermo-sensitive substrates without the need of material postprocessing. In this study, the authors report on the growth of zinc oxide films by direct plasma-enhanced atomic layer deposition at near room temperature. Diethyl zinc and oxygen plasma were used as the precursor and coreactant, respectively. The process was optimized with respect to the precursor and coreactant dosing as well as to the purging times, which ultimately resulted in saturated atomic layer deposition growth. The so-obtained films exhibit a polycrystalline pattern with a (100) texture and low amount of incorporated carbon. Furthermore, the possibility to tune crystallite size, refractive index, and bandgap of the films by adapting the plasma radio-frequency power is demonstrated

Crystallization of Carbamazepine in Proximity to Its Precursor Iminostilbene and a Silica Surface

Amorphous films of the anticonvulsant drug carbamazepine are easily accessible by various methods, while the crystallization into specific polymorphs represents a challenging and time-consuming task. In this work, the crystallization of drop cast carbamazepine at silica surfaces is investigated by atomic force microscopy and both <i>in situ</i> and <i>ex situ</i> grazing incidence X-ray diffraction. The pristine films grow with low crystallization rates into a triclinic polymorph, exhibiting poor orientational order within films. However, if iminostilbene, a chemical precursor of carbamazepine, is added to the solution, enhanced crystallization rates result. The individual components crystallize phase-separated upon solvent evaporation without the formation of cocrystals. Iminostilbene reduces the time scale of carbamazepine crystallization from several hours to minutes. Besides the change in crystallization dynamics, iminostilbene induces order to the carbamazepine crystallites, evident as a 110 texture. <i>In situ</i> data of intermixed solutions demonstrate that iminostilbene crystallization occurs first. The iminostilbene crystals then act as templates for carbamazepine growth, whereby fully epitaxial growth is suggested from the results. The findings motivate such an approach for other systems, as this solution-processed, intrinsic epitaxial behavior might be employed in up-scaled manufacturing processes