Materials Today Communications 7 (2016) 1–10 Contents lists available at ScienceDirect Materials Today Communications journal homepage: www.elsevier.com/locate/mtcomm Carbon fibers prepared from ionic liquid-derived cellulose precursors Johanna M. Spörl a,b , Antje Ota b , Sunghee Son c , Klemens Massonne c , Frank Hermanutz b , Michael R. Buchmeiser a,b,∗ a Lehrstuhl für Makromolekulare Stoffe und Faserchemie, Institut für Polymerchemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany b Institut für Textilchemie und Chemiefasern (ITCF), Körschtalstr. 26, D-73770 Denkendorf, Germany c BASF SE, 67056 Ludwigshafen, Germany a r t i c l e i n f o Article history: Received 29 January 2016 Accepted 3 February 2016 Available online 23 February 2016 Keywords: Cellulose Ionic liquids Dry–wet-spinning Carbon fibers TGA-MS TGA-IR Raman spectroscopy WAXS a b s t r a c t Cellulose derivative fibers were prepared via phosphorylation of cellulose with the ionic liquid (IL) 1,3- dimethylimidazolium methyl-H-phosphonate [MMIM] + [MMP] − in the spinning dope and subsequent fiber formation in a dry–wet-spinning process. The thus obtained precursor fibers were carbonized at different temperatures. In order to receive carbon fibers in high carbonization yields, the degree of sub- stitution (DS) was adjusted. The rheological behavior of the spinning dope was studied and the spinning and carbonization parameters were optimized. Moreover, the precursor fiber tensile and structural prop- erties were compared to pure cellulose fibers. According to thermal analysis coupled with evolved gas analysis (TGA-EGA) of the derivative and pure cellulose fibers, the carbonization yields could be almost doubled via the applied functionalization of cellulose and differences in the relative amounts of released gases during carbonization were studied. Both, precursor and carbon fibers were analyzed by, wide-angle X-ray scattering (WAXS), Raman spectroscopy, scanning electron microscopy (SEM), and tensile testing. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction The demand for carbon fibers (CFs) is expected to increase within the next years from 51,000 t in 2015 to 8900 t in 2020 [1]; however, to establish CF-based materials in price-sensitive prod- ucts, e.g. in automotive industry’s large-scale production, their production costs have to be significantly reduced. Due to ris- ing raw material and energy costs, worldwide research efforts address the development of alternative precursors besides of poly(acrylonitrile)- (PAN-) based precursor fibers from which cur- rently up to 98% of all CFs are prepared of [1–3]. An additional drawback of PAN-based CFs is that large amounts of toxic pyrolysis products are formed during pyrolysis, which requires an extensive exhaust-gas after treatment. In this respect, precursor polymers from biogenic resources are of special interest because they are available inexpensively from renewable resources. Cellulose is the oldest known CF-precursor material. Substantial research activ- ity on cellulosic precursors was observed in the 1950–1970s, but disadvantages such as high production costs at low yields ∗ Corresponding author at: Lehrstuhl für Makromolekulare Stoffe und Faserchemie, Institut für Polymerchemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany. E-mail address: michael.buchmeiser@ipoc.uni-stuttgart.de (M.R. Buchmeiser). and the much more promising findings with PAN-based precur- sors ultimately resulted in casing research on this technology. Today, interest in producing CFs from cellulose has arisen again for economic and ecological reasons. Recent developments such as processing cellulose from ionic liquids (ILs) open new possibilities in chemical and physical modification of fibers and promote latest research activities to study cellulosic precursors for CFs. Because of their discontinuous character, natural cellulose fibers cannot be used as precursors for high-performance CFs. In contrast, possible precursor materials are man-made regenerated cellulose fibers, like viscose or lyocell, which can be produced as endless fil- aments of well-defined dimension and high purity. Viscose rayon is produced by xanthation of alkali cellulose with CS 2 in order to dissolve it in aqueous NaOH. When the solution is spun into a coag- ulation bath containing H 2 SO 4 and Na 2 SO 4 , CS 2 is eliminated and mostly reused in the process. However, the process requires huge efforts in waste treatment, not only because of the large amounts of waste water, but also because of residual H 2 S and CS 2 in the exhaust-gas [4]. Zinc salts in the coagulation bath enable the for- mation of skin/core structures, whereby the thickness of the skin depends on the diffusion of zinc ions into the fiber. The skin con- tains many small crystallites imparting strength, whereas the core contains fewer but larger crystallites. These rayon fibers are tech- nically used as tire cords [5,6]. Viscose rayon suffers from a porous morphology, an irregular fiber cross-section and transversal cracks. http://dx.doi.org/10.1016/j.mtcomm.2016.02.002 2352-4928/© 2016 Elsevier Ltd. All rights reserved.