Preparation of Biopolymer Fibers by Electrospinning from Room Temperature Ionic Liquids

Abstract

Electrospinning is a versatile process used to prepare micro-and nano-sized fibers from various polymers dissolved in volatile solvents. In this report, cellulose and cellulose-heparin composite fibers are prepared from nonvolatile room temperature ionic liquid (RTIL) solvents by electrospinning. RTILs are extracted from the biopolymer fiber after the fiber formation using a cosolvent. Micron to nanometer sized, branched fibers were obtained from 10% (w/w) concentration of polysaccharide biopolymer in RTIL solution with an applied voltage of 15-20 kV. Cellulose-heparin composite fibers showed anticoagulant activity, demonstrating that the bioactivity of heparin remained unaffected even on exposure to a high voltage involved in electrospinning. IntroductionElectrospinning is a widely used simple technique to prepare micron-to nanometer-sized fibers of various polymers. 1 Electrospun fibers find applications in the making of fiber-reinforced composites, membranes, biosensors, electronic and optical devices, and as enzyme and catalytic supports. 2 The electrospinning technique is useful even in large-scale manufacturing environments such as textile industries. 3 A variety of novel tissue engineering scaffolds have been prepared by electrospinning various synthetic and natural biodegradable polymers. 4 However, the range of the polymers that can be electrospun is still limited by the availability of volatile solvents and their limited capability of dissolving polymers of different types. In this report, we conceive of making electrospun fibers from a relatively novel solvent system: room temperature ionic liquids (RTILs). RTILs have become more important in a wide array of chemical processes owing to their capability of dissolving both polar and nonpolar compounds. 5 Other desirable properties of RTILs include low or zero vapor pressure, low melting point, large liquidus range, high thermal stability, large electrochemical window, and recyclability. 6 Further, the properties of an RTIL can be modified by adjusting the structures of its anion or cation or both, and hence, RTILs are also called designer solvents. RTILs have proven to be a promising solvent system for the reactions involving biopolymers such as enzymes 7 and carbohydrates. [8][9][10] The successful application of RTILs in electrospinning could increase the number and types of materials from which the fibers can be made.Electrospinning can be considered as a derivative of the electrospray process, as both use high voltage to form a liquid jet. In the electrospinning process, a polymer solution is held by its surface tension at the end of a capillary. When a sufficiently large electric field is applied, the solution at the tip of the capillary elongates to form a cone because of coupled effects of the electrostatic repulsion within the charged droplet and attraction to a grounded electrode of opposite polarity. As the strength of the electric field is increased, the charge overcomes the surface tension, and a fine jet is ejected from the apex of the cone...

Effect of methylimidazole on cellulose/ionic liquid solutions and regenerated material therefrom

“…In the last decade, ILs as solvents for biomass in general and cellulose in particular have been widely investigated [5][6][7] since 2002 when Swatloski published the pioneering work on dissolution of cellulose in 1-butyl-3-methylimidazolium chloride (BMIMCl) [8]. This relatively new solvent class has shown great versatility in the field of cellulose technology, including dissolution for regeneration purposes [9,10], homogeneous derivatization [11,12], and biomass processing including wood component separation [13][14][15]. The ILs that are able to dissolve cellulose include several classes of cations and a multitude of anions.…”

Cellulose modification and shaping – a review

“…Several groups have studied the possibility to produce cellulose nanofibers by applying different solvents including NMMO, DMAc/LiCl, and ILs [86][87][88][89]. As an example, fibers produced from cellulose dissolved in ILs were coagulated in water or ethanol and had diameters in the range of a few hundred nanometers up to some micrometers, depending on cellulose concentration.…”

Green Composites from Ionic Liquid-Assisted Processing of Sustainable Resources: A Brief Overview

“…100-200 μm with higher thermal stability than that of gel made from the same biopolymers in [bmim] [Cl]. Branched fibers with the size range of micro-to nanometer were extruded from 10 % (w/w) of celluloseheparin solution in the IL by using electrospinning technique [40]. …”