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.
Highlights
Cellulose, the main constituent of plant cell walls, is a linear polysaccharide (Figure 1), which is mainly used to produce paper
Many studies were performed and described in literature that concerns the preparation of films from Nano crystalline cellulose (NCC)/polymer mixtures in aqueous media [25], more recently nano cellulose paper was applied as substrate and gate dielectric to produce flexible field effect transistors [26] and electro-optical sensors [27]
In order to understand the origin of the intrinsic curvature observed for cellulosic liquid crystalline materials, Magnetic Resonance Imaging (MRI) experiments were performed on different acetoxypropylcellulose (APC) dimethylacetamide (DMac) solutions
Summary
The main constituent of plant cell walls, is a linear polysaccharide (Figure 1), which is mainly used to produce paper. In 1976, Gray reported that concentrated solutions of cellulose derivatives could self-assemble into ordered phases [1] Those liquid crystalline phases displayed colors that changed with concentration and viewing angle, which were attributed to a cholesteric structure. Many studies were performed and described in literature that concerns the preparation of films from NCC/polymer mixtures in aqueous media [25], more recently nano cellulose paper was applied as substrate and gate dielectric to produce flexible field effect transistors [26] and electro-optical sensors [27]. Due to the intrinsic curvature of the system micro-jets swinging as well as micro/nano fibers winding and overwinding, self-motions could be observed and controlled by adjusting temperature and electrospun experimental parameters These cellulose-based materials mimic at the micro/nano scale the helical shapes observed, for example, in tendrils and their motion and mechanical adaptability could be reproduced. Liquid Crystalline Solutions Studied by Nuclear Magnetic Resonance (NMR) Methods
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