From Cellulosic Based Liquid Crystalline Sheared Solutions to 1D and 2D Soft Materials

Abstract

Liquid crystalline cellulosic-based solutions described by distinctive properties are at the origin of different kinds of multifunctional materials with unique characteristics. These solutions can form chiral nematic phases at rest, with tuneable photonic behavior, and exhibit a complex behavior associated with the onset of a network of director field defects under shear. Techniques, such as Nuclear Magnetic Resonance (NMR), Rheology coupled with NMR (Rheo-NMR), rheology, optical methods, Magnetic Resonance Imaging (MRI), Wide Angle X-rays Scattering (WAXS), were extensively used to enlighten the liquid crystalline characteristics of these cellulosic solutions. Cellulosic films produced by shear casting and fibers by electrospinning, from these liquid crystalline solutions, have regained wider attention due to recognition of their innovative properties associated to their biocompatibility. Electrospun membranes composed by helical and spiral shape fibers allow the achievement of large surface areas, leading to the improvement of the performance of this kind of systems. The moisture response, light modulated, wettability and the capability of orienting protein and cellulose crystals, opened a wide range of new applications to the shear casted films. Characterization by NMR, X-rays, tensile tests, AFM, and optical methods allowed detailed characterization of those soft cellulosic materials. In this work, special attention will be given to recent developments, including, among others, a moisture driven cellulosic motor and electro-optical devices.

Lignin-Assisted Stabilization of an Oriented Liquid Crystalline Cellulosic Mesophase, Part B: Toward the Molecular Origin and Mechanism

“…Building on these studies, we recently demonstrated that organosolv lignin drastically stabilizes the shear-induced oriented structure of hydroxypropyl cellulose, the so-called band texture . The band texture is a well-known phenomenon for LCPs. − The bulk macromolecular relaxation of the elastic energy stored in the texture occurs in a sinoidal or zigzag manner and appears as a banded microstructure under crossed polarizers. − In our prior study, we revealed that the stability of the band texture was not only drastically increased by the presence of organosolv lignin but further allowed the manufacture of highly anisotropic “banded films” upon drying. In this way, blend films were prepared exhibiting an increase in modulus and tensile strength of up to 500% compared to pure HPC, i.e., values of 2.7 GPa and 60 MPa, respectively, for blend films containing 30% lignin (by weight).…”

Lignin in Bio-Based Liquid Crystalline Network Material with Potential for Direct Ink Writing

“…The possibility to lock the characteristic shear-induced band texture by chemical cross-linking has also been reported for HPC. − Based on the retention of this specific supramolecular arrangement, Godinho and her co-workers ,, drew attention to cellulosic LCPs as potential network materials for soft stimulus-responsive devices. Furthermore, an elastomer-like behavior was observed by Sena et al, who locked the band texture of acetylated HPC by cross-linking with a diisocyanate.…”

Multimode quantum states with single photons carrying orbital angular momentum

“…There are various types of defects, in which the spiral (screw) defects are also very common in the process of fabricating microstructures. The characteristics of these defects have been described in refs 43 and 44 . In the following, we discuss how to identify the spiral defects by using these states.…”