Controlled Mesoscopic Growth of Polymeric Fibers Using Liquid Crystal Template

A review of advanced helical fibers: formation mechanism, preparation, properties, and applications

As a unique structural form, helical structures have a wide range of application prospects. In the field of biology, helical structures are essential for the function of biological macromolecules such as proteins, so the study of helical structures can help to deeply understand life phenomena and develop new biotechnology. In materials science, helical structures can give rise to special physical and chemical properties, such as in the case of spiral nanotubes, helical fibers, etc., which are expected to be used in energy, environment, medical and other fields. The helical structure also has unique charm and application value in the fields of aesthetics and architecture. In addition, helical fibers have attracted a lot of attention because of their tendrils' vascular geometry and indispensable structural properties. In this paper, the development of helical fibers is briefly reviewed from the aspects of mechanism, synthesis process and application. Due to their good chemical and physical properties, helical fibers have a good application prospect in many fields. Potential problems and future opportunities for helical fibers are also presented for future studies.

Effect of smectic polymers on cholesteric liquid crystals

Composite materials made of polymers and liquid crystals have been widely employed in smart windows, optical filters, and bistable displays. However, it is often difficult to decipher the role of the polymer network architecture on the alignment and the texture of liquid crystals. In this study, we use a simple model system where a small amount of polymerizable liquid crystalline monomer is mixed in a liquid crystal that exhibits both a smectic phase and a cholesteric phase with a large helical pitch. By cross-linking the monomer in the smectic phase, the liquid crystal textures become significantly altered. The existence of a polymer network not only creates resistance to form a helix and therefore hinders the formation of cholesteric fingerprints but also modifies the structure of the cholesteric texture. We investigate the effects of changing the concentration of chiral dopant and monomer on the formation and growth of the cholesteric fingerprint texture during the phase transition and on the width of the fingerprints. We find that, within a certain parameter range, the cholesteric fingerprints do not depend on the concentration of the chiral dopant. We explain this phenomenon by hypothesizing that the polymer network acts as a bulk alignment field.

Fabrication of Zigzag Parylene Nanofibers in Liquid Crystals with Electric Field-Induced Defect Structures

Liquid crystals (LCs) have been adopted to induce tunable physical properties that dynamically originated from their unique intrinsic properties responding to external stimuli, such as surface anchoring condition and applied electric field, which enables them to be the template for aligning functional guest materials. We fabricate the fiber array from the electrically modulated (in-plain) nematic LC template using the chemical vapor polymerization (CVP) method. Under an electric field, an induced defect structure with a winding number of -1/2 contains a periodic zigzag disclination line. It is known that LC defect structures can trap the guest materials, such as particles and chemicals. However, the resulting fibers grow along the LC directors, not trapped in the defects. To show the versatility of our platform, nanofibers are fabricated on patterned electrodes representing the alphabets 'CVP.' In addition, the semifluorinated moieties are added to fibers to provide a hydrophobic surface. The resultant orientation-controlled fibers will be used in controllable smart surfaces that can be used in sensors, electronics, photonics, and biomimetic surfaces.