Macro- and Microstructural Evolution during Drying of Regenerated Cellulose Beads

Abstract

The macro- and microstructural evolution of water swollen and ethanol swollen regenerated cellulose gel beads have been determined during drying by optical microscopy combined with analytical balance measurements, small-angle X-ray scattering (SAXS), and wide-angle X-ray scattering (WAXS). Two characteristic length scales, which are related to the molecular dimension of cellulose monomer and elongated aggregates of these monomers, could be identified for both types of beads by SAXS. For ethanol swollen beads, only small changes to the structures were detected in both the SAXS and WAXS measurements during the entire drying process. However, the drying of cellulose from water follows a more complex process when compared to drying from ethanol. As water swollen beads dried, they went through a structural transition where elongated structures changed to spherical structures and their dimensions increased from 3.6 to 13.5 nm. After complete drying from water, the nanostructures were characterized as a combination of rodlike structures with an approximate size of cellulose monomers (0.5 nm), and spherical aggregates (13.5 nm) without any indication of heterogeneous meso- or microporosity. In addition, WAXS shows that cellulose II hydrate structure appears and transforms to cellulose II during water evaporation, however it is not possible to determine the degree of crystallinity of the beads from the present measurements. This work sheds lights on the structural changes that occur within regenerated cellulose materials during drying and can aid in the design and application of cellulosic materials as fibers, adhesives, and membranes.

Humidity‐Induced Nanoscale Restructuring in PEDOT:PSS and Cellulose Nanofibrils Reinforced Biobased Organic Electronics

“…X‐ray and neutron scattering techniques are suited methods to follow dynamic processes in‐situ and have successfully resolved the nanoscale re‐assembly of CNF‐based 3D objects as well as in thin films during wet and drying conditions. [ 23 ] [ 24,25 ] Grazing incidence X‐ray scattering was used to study and model the organization of PEDOT:PSS on individual CNFs. [ 26 ] In fact, GISAXS was used on samples prepared by spray deposition to study the structural changes of nanoparticles during thermal annealing.…”

Molecular‐Scale Design of Cellulose‐Based Functional Materials for Flexible Electronic Devices

“…For example, Li et al. [ 116 ] dripped a DMAc/LiCl solution with cellulose dissolved in ethanol to obtain solidified cellulose spherical droplets, which provided an efficient separation technique for impurities and large particles (Figure 6c). Mystek et al.…”

“…Reproduced with permission. [ 116 ] Copyright 2020, American Chemical Society. d) In situ modification process and SEM images of cellulose microbeads.…”

“…Combining cellulose dissolution systems with molecular hybridization and self-assembly has been used to develop other cellulose-based functional materials, such as ionic gels, microspheres, and fibers. [4,[114][115][116][117][118] Cellulose-based ionic gels are ionically conductive and flexible, allowing them to be directly used as substrates and conductors in sensors and electronic skin. [4,119] Wang et al [29] fabricated a cellulose/chitosan supramolecular ionic gel using a simple two-step method involving chemical cross-linking in a homogeneous solution.…”

“…[29] Cellulose-based nanospheres have emerged in chromatographic separation processes and biological carriers. For example, Li et al [116] dripped a DMAc/ LiCl solution with cellulose dissolved in ethanol to obtain solidified cellulose spherical droplets, which provided an efficient separation technique for impurities and large particles (Figure 6c). Mystek et al [120] developed an in situ modification technology called the drop precipitation method that could easily and conveniently control the composition and structure of Reproduced with permission.…”