The self-assembly of diblock copolymers provides a convenient route to the formation of mechanically robust films with precise and tunable periodic arrangements of two physically demixed but chemically linked polymeric materials. Chemoselective transport membranes may be realized from such films by selective partitioning of an active species into one of the polymer domains. Here, lithium ions were selectively sequestered within the poly(ethylene oxide) block of a liquid crystalline diblock copolymer to form polymer electrolyte membranes. Optimization of the membrane conductivity mandates alignment of self-assembled structures such that conduction occurs via direct as opposed to tortuous transport between exterior surfaces. We show here that magnetic fields can be used in a very simple and scalable manner to produce highly aligned hexagonally packed cylindrical microdomains in such membranes over macroscopic areas. We systematically explore the dependence of the ionic conductivity of the membrane on both temperature and magnetic field strength. A surprising order of magnitude increase in conductivity relative to the nonaligned case is found in films aligned at the highest magnetic field strengths, 6 T. The conductivity of field aligned samples shows a nonmonotonic dependence on temperature, with a marked decrease on heating in the proximity of the order-disorder transition of the system before increasing again at elevated temperatures. The data suggest that domain-confined transport in hexagonally packed cylindrical systems differs markedly in anisotropy by comparison with lamellar systems.

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Thermal cross-linking is widely used to impart stability or improved mechanical properties to layer-by-layer (LbL) assemblies. However, the kinetics of thermal cross-linking within LbL films is not well understood. Furthermore, because LbL films are generally ultrathin (<100 nm), the influence of confinement on cross-linking kinetics is potentially substantial. Using temperature-controlled ellipsometry, differential scanning calorimetry, and thermal gravimetric analysis, we are able to accurately track amide cross-linking within poly(allylamine hydrochloride)/poly(acrylic acid) LbL films. The rate of amidation is strongly influenced by film thickness and surface chemistry, which indicates that the observed "confinement effects" are primarily related to the catalytic contribution of hydroxyl groups present on the substrate's surface. The analytical techniques presented herein highlight new ways to access thermochemical information within ultrathin LbL assemblies.

A simple, yet very flexible robotic dipping system for the preparation of functional thin films is presented. These films are deposited onto a substrate using the layer-by-layer assembly technique. The robot alternately dips a substrate into aqueous mixtures containing oppositely charged or otherwise complementary species. Samples can be spray rinsed (a unique feature of this robot relative to others created for thin film deposition) and blow dried after each dip. Dipping, rinsing, and drying times are adjustable and up to twelve mixtures can be deposited in any order. An example 20-bilayer film was prepared using aqueous mixtures of carbon black stabilized with polyethylenimine and poly(acrylic acid). This film exhibits low resistivity (&lt;0.2Ω∙cm) and is free of the porosity and brittleness that are characteristic of highly filled polymer composites. The robotic dipping system is especially useful for films requiring more than tenbilayers and a variety of different layers.

The layer-by-layer assembly technique was used to create electrically conductive films with poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT-PSS) and branched polyethylenimine (BPEI). Titanium dioxide (TiO(2)) and carbon black were used to prevent UV-degradation of these PEDOT-PSS thin film assemblies. Film growth and conductivity were studied, while varying composition and examining the effect of UV absorbing particles on the electrical conductivity. All films showed similar initial sheet resistances, but after exposure to 365 nm UV light for 9 days (correlating to approximately 4 years of sunlight), the films containing TiO(2) were up to 250 times more conductive. Additionally, the TiO(2) containing films were 27% more optically transparent than films made with PEDOT in the absence of TiO(2). The addition of colloidal titania allows the useful life of the PEDOT films to be extended without the detrimental effects of decreased transparency. Doping the PEDOT with dimethylsulfoxide produced eight bilayer films that were almost 6 times more conductive. However, the degradation rate for the doped PEDOT films without TiO(2) was 10 times greater than the doped films with TiO(2).