Polymeric films can be grown by a sequential, self-limiting surface chemistry process known as molecular layer deposition (MLD). The MLD reactants are typically bifunctional monomers for stepwise condensation polymerization and can yield completely organic films. The MLD of organic–inorganic hybrid polymers can also be accomplished using a bifunctional organic monomer and a multifunctional inorganic monomer. In this work, the growth of a poly(aluminum ethylene glycol) polymer is demonstrated using the sequential exposures of trimethylaluminum (TMA) and ethylene glycol (EG). These hybrid polymers, known as alucones, were grown over a wide range of temperatures from 85 to 175 °C. In situ quartz crystal microbalance and ex situ X-ray reflectivity experiments confirmed linear growth of the alucone film versus number of TMA/EG reaction cycles at all temperatures. The alucone growth rates decreased at higher temperatures. Growth rates varied from 4.0 Å per cycle at 85 °C to 0.4 Å per cycle at 175 °C. In situ Fourier transform infrared spectroscopy was used to monitor the surface reactions during alucone MLD. Ex situ FTIR spectroscopy, X-ray photoelectron spectroscopy, and X-ray reflectivity measurements were also employed to determine the chemical composition, thickness, and density of the alucone films. These ex situ studies revealed that the alucone films grown on Al2O3 ALD surfaces evolved under ambient conditions before reaching a stable state. Alucone films capped with rapid SiO2 ALD displayed much more stability than alucone films grown on Al2O3 ALD surfaces. These results indicated that H2O may facilitate the chemical transformation of the alucone MLD films. The alucone films represent a new class of organic–inorganic hybrid polymers. Modification of this basic alucone MLD chemistry with use of other diols or other bifunctional monomers can produce different alucone polymers with variable properties.

Single Al2O3 atomic layer deposition (ALD) films on polymers have demonstrated excellent gas diffusion barrier properties. Further improvements can be achieved using multilayers of Al2O3 ALD layers with other inorganic layers. In this study, multilayers of Al2O3 ALD and rapid SiO2 ALD were grown on Kapton and heat-stabilized polyethylene naphthalate substrates. Transmission rates for tritium through the films were measured using the radioactive HTO tracer method. Comparison with previous Ca tests and tritium exchange experiments with alcohols indicated that the tritium in HTO may diffuse as either molecular HTO or atomic tritium. Assuming that the tritium diffuses only as HTO, single Al2O3 ALD films reduced the effective water vapor transmission rate (WVTR) to ∼1 × 10-3 g/m2/day. When the Al2O3 ALD film was directly exposed to the saturated H2O/HTO vapor pressure, the barrier properties deteriorated markedly after 4−5 days. Al2O3 ALD barriers that were not subjected to direct H2O/HTO exposure indefinitely maintained low tritium transmission rates (TTRs). Rapid SiO2 ALD layers deposited on the Al2O3 ALD layer improved the diffusion barrier properties and protected the Al2O3 ALD layers from H2O corrosion. The effective WVTR also reduced to ∼1 × 10-4 g/m2/day for the Al2O3/SiO2 ALD bilayer. Multilayers of Al2O3/SiO2 bilayers initially further reduced the TTRs. Two Al2O3/SiO2 bilayers reduced the effective WVTR to ∼5 × 10-5 g/m2/day. Multilayers composed of >2 Al2O3/SiO2 bilayers displayed degraded performance and effective WVTRs that were comparable with the single Al2O3 ALD film. These multilayer barriers may have cracked during handling and mounting as a result of brittleness at larger thicknesses. The barrier improvement observed for one Al2O3/SiO2 bilayer and two Al2O3/SiO2 bilayers could not be explained using laminate theory. The improvement suggests that the rapid SiO2 ALD layer successfully closed pinhole defects in the Al2O3 ALD layer.

Fatty acid has recently received considerable interest as a possible precursor for producing renewable hydrocarbon. In this study, we investigated hydrothermal catalytic deoxygenation of palmitic acid to produce paraffin over a Ni/ZrO 2 catalyst with no or low-pressure (100 psi) external supply of H 2. The results show that the presence of water greatly improved conversion of palmitic acid and paraffin yield. Significant improvement was attributed to the formation of in-situ H 2. Without an external H 2 supply, a 64.2 C% conversion of palmitic acid was achieved in the presence of water, while only a 17.2 C% conversion was achieved without water. The results also show that the presence of water suppressed the side reactions of palmitic acid, specifically ketonization and esterification. We concluded that, compared with decarboxylation and hydrodeoxygenation, decarbonylation was the major route for palmitic acid deoxygenation catalyzed by Ni/ZrO 2. Varieties of shorter-chain paraffin (C 8-C 14) were formed through hydrogenolysis, which also produced a considerable amount of CH 4. A viable reaction pathway for hydrothermal catalytic deoxygenation of palmitic acid in the presence of Ni/ZrO 2 was suggested. The results show that hydrogenolysis and decarbonylation were the major reactions that occurred. This study demonstrates that this hydrothermal catalytic process is a promising approach for producing liquid paraffin (C 8-C 15) from fatty acids under no or low-pressure H 2 .

Despite extensive studies on hydrogen production via steam reforming of alcohols and sugar alcohols, catalysts typically suffer a variety of issues from poor hydrogen selectivity to rapid deactivation. Here, we summarize recent advances in fundamental understanding of functionality and structure of catalysts for alcohol/sugar alcohol steam reforming, and provide perspectives on further development required to design highly efficient steam reforming catalysts.