Dry‐jet wet electrospinning of native cellulose microfibers with macroporous structures from ionic liquids

Abstract

In this study, we have provided a review of electrospun cellulose micro/nanofibers from ionic liquids (ILs) and cosolvents from which we identify a lack of previous studies focusing on the structural morphology of the dry-jet wet electrospun native cellulose fibers from ILs. We have therefore aimed to investigate factors influencing the structural morphology of cellulose/IL electrospun fibers and investigate the coagulation parameters on this morphology. The electrospinning of 10% w/v cellulose/([C2MIM][OAc]/MIM) (1/1, v/v) solution was shown to produce macroporous fibers with average diameters of 2.8 AE 1.4 μm with pore sizes from 100 to 200 nm. We have found that coagulation bath type and immersion time affect the morphological structure of the electrospun fibers. The fiber spinnability, formation, and morphological structure are mainly dependent on the method used to collect and coagulate/solidify the fibers. The physical properties of the dissolved cellulose were measured and these are discussed in terms of the solution spinnability. The structural morphology of the electrospun cellulose fibers was characterized by scanning electron microscopy, and finally the extraction of IL from the fiber body was confirmed by nuclear magnetic resonance. The electrospun cellulose fibers morphology shows the formation of both micron and nanometer sized fibers with different morphological "macroporous" structures.

Cellulose-based fiber spinning processes using ionic liquids

“…Given that cellulose is one of the oldest polymers used in manufacture of fibers, it has been taken into consideration and proposed for production of nanofibers. Regenerated cellulose ultrafine fibers in the nanometer range due to special morphology and geometrical dimensions, possess improved properties different from conventional micro fibers, interesting for industrial applications (Bazbouz et al 2019;Otsuka et al 2017;Zhang et al 2019c). Electrospinning is a simple and effective process to produce the polymeric nanofibrous materials for a wide range of applications.…”

“…The nanofibrous structures composed of electrospun cellulose fibers generally exhibit several excellent characteristics, likely very large surface area over volume ratio, high porosity with a very small pore size, mechanical reinforcement, and enhanced surface reactivity, which make them appropriate candidates for diverse technical, industrial, and biomedical applications such as functional textiles, filtration membranes, tissue engineering scaffolds, wound healing, drug delivery, etc. (Ahn et al 2012a, b;Bazbouz et al 2019;de Campos et al 2019;Devarayan et al 2013;Freire et al 2011;Kang et al 2013;Liu et al 2017;Mokhena and John 2019;Nechyporchuk et al 2016;Norrrahim et al 2018;Otsuka et al 2017;Zhang et al 2019c;Zheng et al 2014). In contrast to the advantages, due to the poor solubility of cellulose in volatile solvents, the electrospinning of cellulose is chalenging.…”

“…Cellulose fibers slowly solidify in the coagulation bath in which the IL is replaced by a coagulant solvent like water or alcohol. This solvent is then removed from these hydrogel fibers by either standard desiccation or freeze-drying (Bazbouz et al 2019;Frey 2008;Mahmood et al 2017;Zheng et al 2014). Parallel copper wires rotating drum or a rotating cylinder partially submerged in a coagulation bath, have been also used as collectors (Härdelin et al 2013;Işık et al 2015).…”

“…Such researches have suggested to use a co-solvent beside ILs to modulate the viscosity, and surface tension of the solvent, to decrease the entanglement density of the system, and to enhance electrical conductivity, and processability of cellulose in the solvent (Ahn et al 2012a;Freire et al 2011;Härdelin et al 2012;Quan et al 2010;Xu et al 2008). In some other experimental works, the parameters affecting the spinning process and structural morphology of cellulose/IL electrospun fibers, including the type of the cellulose (Ahn et al 2012b;Bazbouz et al 2019;Kang et al 2013;Polaskova et al 2013), solution features (concentration and viscosity, cellulose molecular weight, IL solvent system) (Ahn et al 2012a;Freire et al 2011;Härdelin et al 2012;Quan et al 2010;Xu et al 2008), and coagulation parameters (coagulant liquid type, immersion time, and method to collect and solidify the fibers) (Bazbouz et al 2019), have been investigated.…”

“…Depending on the molecular weight, polymer solutions can be electrospun within a specified concentration range. An optimal solution concentration gives an adequate viscosity for the formation of continuous uniform bead free fibers (Bazbouz et al 2019). Quan et al (2010) reported that the diameter and morphology of the electrospun cellulose fibers were affected by the concentration of cellulose in the IL ([Bmim]Cl) by influencing the viscosity of the solution.…”