Composed exclusively of organic components, polyaniline (PANi), graphene, and double-walled nanotubes (DWNTs) are alternately deposited from aqueous solutions using a layer-by-layer assembly. The 40 quadlayer thin film (470 nm thick) exhibits electrical conductivity of 1.08 × 10(5) S m(-1) and a Seebeck coefficient of 130 μV K(-1) , producing a thermoelectric power factor of 1825 μW m(-1) K(-2) .

The influence of clay-layer spacing on gas barrier thin films of sodium montmorillonite clay and polyelectrolytes, created via layer-by-layer assembly, is investigated. The alternate deposition of polymers and clay leads to the assembly of a nanobrick wall structure that is highly impermeable to gases. In an effort to tailor the thickness (or spacing) between clay layers, films with differing numbers of polymer layers between clay depositions were examined. Films analyzed for their thickness, clay concentration, transparency, nanostructure, and oxygen barrier as a function of layers (or spacing) between clay depositions reveal linear growth, optical clarity, and low OTR at 100 nm thick and containing only four clay layers. An optimal thickness between clay layers appears to exist for achieving the highest oxygen barrier LbL films (PO2 < 1 × 10–21 cc(STP)·cm/(cm2·s·Pa)). This knowledge can ultimately minimize deposition steps and lead to decreased thin film fabrication times.

The thermoelectric properties of fully organic nanocomposites were investigated, for which meso‐tetra(4‐carboxyphenyl) porphine (TCPP) and poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) were used as instrinically conductive and semiconducting stabilizers, respectively. The electrical conductivity (σ) of these dual‐stabilizer organic composites increased to approximately 9500 S m−1 as the concentrations of both the multiwalled carbon nanotubes (MWNTs) and PEDOT:PSS were increased. The thermopower (or Seebeck coefficient, S) and thermal conductivity, however, remained relatively unaffected by the increase in concentration (≈40 μV K−1 and ≈0.12 W m−1 K−1, respectively). Replacing MWNTs with double‐walled carbon nanotubes (DWNTs) increased σ and S to approximately 96 000 S m−1 and 70 μV K−1, respectively, at 40 wt % DWNTs. This study suggests that σ and S can be simultaneously tailored by using multiple stabilizing agents to affect the transport properties of the junctions between nanotubes. Combining semiconducting and intrinsically conductive molecules as CNT‐stabilizers has led to a power factor that is among the best for a completely organic, free‐standing film (≈500 μW m−1 K−2). These flexible, segregated‐network nanocomposites now exhibit properties that rival the more conventional inorganic semiconductors, particularly when normalized by the mass.

In an effort to reduce deposition time and number of layers needed to achieve high gas barrier, multilayer films were deposited using 1 s exposures for the first four bilayers (BLs) and 1 min for subsequent dips. Thin-film assemblies of polyethylenimine (PEI) and poly(acrylic acid) (PAA) were deposited onto poly(ethylene terephthalate) [PET] using the layer-by-layer deposition process. Varying the exposure time of PET to polyelectrolyte solutions (i.e., dip time) significantly alters the growth rate of the multilayer thin films. The PEI/PAA system grows linearly with 1 s dip times and exponentially with longer times. Eight bilayers (650 nm) were required to achieve an undetectable oxygen transmission rate (<0.005 cm 3 /(m 2 •day)) using 1 min deposition steps, but this barrier was obtained with only 6 BLs (552 nm) using 1s deposition of the initial layers, reducing total deposition time by 73%. This "shift-time" concept makes layer-by-layer assembly much faster and more commercially feasible.

Layer‐by‐layer (LbL) assembly is a powerful and versatile technique to deposit functional thin films, but often requires a large number of deposition steps to achieve a film thick enough to provide a desired property. By incorporating amine salts into the cationic polyelectrolyte and its associated rinse, LbL clay‐containing nanocomposite films can achieve much greater thickness (>1 μm) with relatively few deposition cycles (≤6 bilayers). Amine salts interact with nanoclays, causing nanoplatelets to deposit in stacks rather than as individual platelets. This technique appears to be universal, exhibiting thick growth with multiple types of nanoclay, including montmorillonite and vermiculite (VMT), and a variety of amine salts (e.g., hexylamine and diethanolamine). The characteristic order found in LbL‐assembled films is maintained despite the incredible thickness. Films assembled in this manner achieve oxygen transmission rates below 0.009 cc m−2 d−1 atm−1 with just 6 bilayers (BLs) of chitosan/VMT deposited. These thick clay‐based thin films also impart exceptional flame resistance. A 2‐BL film renders a 3.2 mm polystyrene plate self‐extinguishing, while an 8‐BL film (3.9 μm thick) prevents ignition entirely. This ability to generate much thicker clay‐based multilayers with amine salts opens up tremendous potential for these nanocoatings in real world applications.

Layer-by-layer assembly from aqueous solutions was used to construct multilayer thin films (<200 nm) comprising polyethylenimine and graphene oxide. Low-temperature (175 °C) thermal reduction of these films improved gas barrier properties (e.g., lower permeability than SiO x ), even under high humidity conditions, and enhanced their electrical conductivity to 1750 S/m. The flexible nature of the aforementioned thin films, along with their excellent combination of transport properties, make them ideal candidates for use in a broad range of electronics and packaging applications.

Layer-by-layer assembly was used to create quadlayers (QLs) of chitosan (CH), poly(acrylic acid) (PAA), CH, and graphene oxide (GO). Electron microscopy confirmed GO coverage over the film and a highly ordered nanobrick wall structure. By varying pH deviation between CH and PAA, a thick and interdiffused polymer matrix was created because of the altered chain conformation. A 5 CH (pH 5.5)/PAA (pH 3)/CH (pH 5.5)/GO QL assembly (48 nm) exhibits very low oxygen permeability (3.9 × 10(-20) cm(3) cm cm(-2) Pa(-1) s(-1)) that matches SiOx barrier coatings. In an effort to maintain barrier performance under high humidity, GO was thermally reduced to increase hydrophobicity of the film. This reduction step increased H2/CO2 selectivity of a 5 QL film from 5 to 215, exceeding Robeson's upper bound limit. This unique water-based multilayer nanocoating is very promising for a variety of gas purification and packaging applications.

In an effort to speed up the layer-by-layer (LbL) deposition technique, electrophoretic deposition (EPD) is employed with weak polyelectrolytes and clay nanoplatelets. The introduction of an electric field results in nearly an order of magnitude increase in thickness relative to conventional LbL deposition for a given number of deposited layers. A higher clay concentration also results with the EPD-LbL process, which produces higher modulus and strength with fewer deposited layers. A 20 quadlayer (QL) assembly of linear polyethyleneimine (LPEI)/poly(acrylic acid)/LPEI/clay has an elastic modulus of 45 GPa, tensile strength of 70 MPa, and thickness of 4.4 μm. Traditional LbL requires 40 QL to achieve the same thickness, with lower modulus and strength. This study reveals how these films grow and maintain a highly ordered nanobrick wall structure that is commonly associated with LbL deposition. Fewer layers required to achieve improved properties will open up many new opportunities for this multifunctional thin film deposition technique.