In an effort to impart light gas (i.e., H2 and He) barrier to polymer substrates, thin films of polyethylenimine (PEI), poly(acrylic acid) (PAA), and montmorrilonite (MMT) clay are deposited via layer-by-layer (LbL) assembly. A five "quadlayer" (122 nm) coating deposited on 51 μm polystyrene is shown to lower both hydrogen and helium permeability three orders of magnitude against bare polystyrene, demonstrating better performance than thick-laminated ethylene vinyl-alcohol (EVOH) copolymer film and even metallized polyolefin/polyester film. These excellent barrier properties are attributed to a "nanobrick wall" structure. This highly flexible coating represents the first demonstration of an LbL deposited film with low hydrogen and helium permeability and is an ideal candidate for several packaging and protection applications.

This work presents the first side-by-side comparison of the two leading multifunctional catalyst designs reported in the literature today for sorption-enhance reforming processes. Twodimensional unsteady-state models were developed to compare the performance of a core-shell multifunctional catalyst, consisting of a calcium-based sorbent core enclosed in a porous shell of methane steam reforming or water-gas shift catalyst, against an equivalent case of a uniformdistributed multifunctional design in which catalyst and sorbent materials are uniformly distributed within the particle. Additionally, these two multifunctional catalyst designs were compared against the conventional two-pellet approach, where the capture and catalytic properties are distinguished into separate pellets. Both multifunctional catalyst designs (i.e. coreshell and uniform-distributed) had greater adsorbent utilization and higher H 2 outlet concentration up to breakthrough time than the conventional two pellet design. The uniformdistributed multifunctional catalyst design had greater adsorbent utilization up to breakthrough conditions as compared to the core-shell design. This behavior may be attributed to the fact that for the uniform-distributed multifunctional, the active catalyst is constantly producing CO 2 next to an adsorbent active site. For the core-shell multifunctional catalyst design, decreasing catalystshell thickness resulted in performance approaching the uniform-distributed case. For the case of exothermic water-gas shift reaction coupled with CO 2 chemisorption, the core-shell design mitigated local bed hot-spot magnitudes by ~40 K.

Multilayer thin films of poly(ethylene oxide) (PEO) and poly(methacrylic acid) (PMAA), deposited via layer‐by‐layer (LbL) assembly from aqueous solutions, are investigated for CO2/N2 separation. Eight and ten bilayer (217 and 389 nm thick, respectively) PEO/PMAA thin films deposited on a 25 μm polystyrene substrate exhibit CO2/N2 selectivities of 142 and 136, respectively. These are the highest reported to‐date for this gas pair separation using a homogeneous polymer film. While further work remains to improve CO2 permeability, these results indicate the potential of LbL assemblies as standalone CO2 separation membranes for low‐flux/high‐purity applications, or as part of a composite and/or mixed‐matrix membrane for high‐flux applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1730–1737