Air-Curable, High-Resolution Patternable Oxetane-Based Liquid Crystalline Photonic Films via Flexographic Printing.

The production of patterned photonic films on a large scale remains a challenge. Here, we report on a new class of photonic materials that are based on oxetane liquid crystals (LCs). Patterned reflective coatings can be produced from these materials on flexible substrates by using flexographic printing. This industrially relevant process allows for upscaling in future applications. Furthermore, the oxetane LCs used do not require an inert atmosphere for photopolymerization, unlike previously described acrylate systems. We show that the flexographic printing process results in excellent alignment, and that the patterns produced display a high resolution. Additionally, we demonstrate that free-standing photonic reflecting foils can also be produced from these materials. Our new oxetane-based patterned iridescent colored materials have potential application for both esthetic purposes as well as anticounterfeit labels.

Directed Self-Assembly of Liquid-Crystalline Molecular Building Blocks for Sub-5 nm Nanopatterning.

The thin-film directed self-assembly of molecular building blocks into oriented nanostructure arrays enables next-generation lithography at the sub-5 nm scale. Currently, the fabrication of inorganic arrays from molecular building blocks is restricted by the limited long-range order and orientation of the materials, as well as suitable methodologies for creating lithographic templates at sub-5 nm dimensions. In recent years, higher-order liquid crystals have emerged as functional thin films for organic electronics, nanoporous membranes, and templated synthesis, which provide opportunities for their use as lithographic templates. By choosing examples from these fields, recent progress toward the design of molecular building blocks is highlighted, with an emphasis on liquid crystals, to access sub-5 nm features, their directed self-assembly into oriented thin films, and, importantly, the fabrication of inorganic arrays. Finally, future challenges regarding sub-5 nm patterning with liquid crystals are discussed.

3D Orientational Control in Self-Assembled Thin Films with Sub-5 nm Features by Light.

While self-assembled molecular building blocks could lead to many next-generation functional organic nanomaterials, control over the thin-film morphologies to yield monolithic sub-5 nm patterns with 3D orientational control at macroscopic length scales remains a grand challenge. A series of photoresponsive hybrid oligo(dimethylsiloxane) liquid crystals that form periodic cylindrical nanostructures with periodicities between 3.8 and 5.1 nm is studied. The liquid crystals can be aligned in-plane by exposure to actinic linearly polarized light and out-of-plane by exposure to actinic unpolarized light. The photoalignment is most efficient when performed just under the clearing point of the liquid crystal, at which the cylindrical nanostructures are reoriented within minutes. These results allow the generation of highly ordered sub-5 nm patterns in thin films at macroscopic length scales, with control over the orientation in a noncontact fashion.

Sub-5 nm Patterning by Directed Self-Assembly of Oligo(Dimethylsiloxane) Liquid Crystal Thin Films.

Highly ordered nanopatterns are obtained at sub-5 nm periodicities by the graphoepitaxial directed self-assembly of monodisperse, oligo(dimethylsiloxane) liquid crystals. These hybrid organic/inorganic liquid crystals are of high interest for nanopatterning applications due to the combination of their ultrasmall feature sizes and their ability to be directed into highly ordered domains without additional annealing.

Improving the Transparency of Ultra-Drawn Melt-Crystallized Polyethylenes: Toward High-Modulus/High-Strength Window Application.

Highly transparent, ultradrawn high-density polyethylene (HDPE) films were successfully prepared using compression molding and solid-state drawing techniques. The low optical transmittance (<50%) of the pure drawn HDPE films can be drastically improved (>90%) by incorporating a small amount (>1 wt %/wt) of specific additives to HDPE materials prior to drawing. It is shown that additives with relatively high refractive index result in an increased optical transmittance in the visible light wavelength which illustrates that the improvement in optical characteristics probably originates from refractive index matching between the crystalline and noncrystalline regions in the drawn films. Moreover, the optically transparent drawn HDPE films containing additives maintain their physical and mechanical properties, especially their high modulus and high strength, which make these films potentially useful in a variety of applications, such as high-impact windows.