With the depletion of fossil oil, a major feedstock for polymers, increased attention has been paid towards the development of sustainable materials derived from renewable resources. Cellulose, the most abundant biomass component, has raised lot of interest to develop new materials used for various applications, ranging from packaging materials, such as the well-known (but currently not produced) cellophane, via textile fibers (i.e. artificial silk) to high tech nano-composites.

Cellulose is an organic polymer consisting of a linear chain of several hundred to over ten thousand ß(1->4) linked D-glucose units, which impart cellulose with unique physical and chemical properties, such as hydrophilicity, degradability and broad chemical variability originating from the high reactivity of OH groups. However, the insolubility of cellulose in water or common organic solvents is the main obstacle limiting the modification of cellulose and its application.

The key to an effective dissolution of cellulose in a solvent lies in the ability of the solvent to disrupt the hydrogen bonding, especially in the crystalline regions of cellulose. Among the different solvents developed in the last decade, ionic liquids (IL), such as BMIMCl, can dissolve up to 25 wt% of cellulosic materials. In this project, we will use cellulose dissolved in ILs to develop (i) novel and sustainable cellulose derivatization protocols and (ii) a new CO2-based process for cellulose regeneration. Both new approaches will consider all metrics of green chemistry and will develop processes that are significantly more sustainable than the state of the art. In this study, we will avoid toxic reagants and large amounts of waste by using simple catalytic procedures (i.e. transesterifications, urethanizations) and thus avoid the commonly employed activated carboxylic acids derivatives used for cellulose modification.[1] Plant oils and their derivatives will be used for the transesterification reactions and supercritical CO2 will be also investigated as reagent in Ugi multicomponent and urethanization reactions.[2, 3, 4]

Another advantage of ionic liquids is their low vapor pressure in agreement with the green chemistry principles. However, it is also a disadvantage, since ionic liquids cannot be recovered by distillation similarly to a “normal” organic solvent. There is therefore a huge interest in developing techniques to efficiently regenerate the ionic liquid from the crude mixtures. For this purpose, supercritical CO2 appears to be promising, since it can efficiently extract organic residues from certain ionic liquids and thus regenerate the pure IL solvent [5] and therefore increase the sustainability of the overall process of cellulose regeneration and modification in ionic liquids.

 

In summary, this project will investigate the modification and regeneration of solubilized cellulose using sustainable approaches in order to obtain new cellulosic materials. Moreover, the new materials will be chemically, thermally as well as mechanically characterized.

The research will be performed in a close collaboration between two academic research groups [at the Karlsruhe Institute of Technology (KIT) in Germany and at the University of Bordeaux (UB) in France]. Both institutions have a strong expertise in the synthesis and characterization of bio-based materials and are academic leaders in sustainable polymer science. The third partner, Solvay, is a world leader in cellulose acetate business. The PhD student will share his/her time between these 3 partners.

[1] A. Schenzel, A. Hufendiek, C. Barner-Kowollik, M.A.R. Meier, Green Chem. 2014, 16, 3266
[2] M. A. R. Meier, J. O. Metzger, U. S. Schubert, Chem. Soc. Rev. 2007, 36, 1788-1802
[3] A. Sehlinger, R. Schneider, M. A. R. Meier, Macromol. Rapid Commun. 2014, 35, 1866
[4] D. B. Dell’Amico, F. Calderazzo, L. Labella, F. Marchetti, G. Pampaloni, Chem. Rev. 2003, 103, 3857
[5] M. C. Kroon, J. van Spronsen, C. J. Peters, R. A. Sheldon, G-J. Witkamp, Green Chem. 2006, 8, 246

Project Partners

Institute of Organic Chemistry, Karlsruhe Institute of Technology, Germany

Laboratory for Chemistry of Organic Polymers (LCPO) Bordeaux, France

Industry Partner: Solvay, Belgium/France

Host Country (employment): Germany


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