Electrospinning Biopolymers from Ionic Liquids Requires Control of Different Solution Properties than Volatile Organic Solvents

We report the correlation between key solution properties and spinability of chitin from the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([C(2)mim][OAc]) and the similarities and differences to electrospinning solutions of nonionic polymers in volatile organic compounds (VOCs). We found that when electrospinning is conducted from ILs, conductivity and surface tension are not the key parameters regulating spinability, while solution viscosity and polymer concentration are. Contrarily, for electrospinning of polymers from VOCs, solution conductivity and viscosity have been reported to be among some of the most important factors controlling fiber formation. For chitin electrospun from [C(2)minn][OAc], we found both a critical chitin concentration required for continuous fiber formation (>0.20 wt %) and a required viscosity for the spinning solution (between ca. 450-1500 cP). The high viscosities of the biopolymer IL solutions made it possible to electrospin solutions with low, less than 1 wt %, polymer concentration and produce thin fibers without the need to adjust the electrospinning parameters. These results suggest new prospects for the control of fiber architecture in nonwoven mats, which is crucial for materials performance.