Synthesis of xylan carbonates - An approach towards reactive polysaccharide derivatives showing self-assembling into nanoparticles.

Xylan phenyl carbonate (XPC) derivatives were prepared and characterized comprehensively. By conversion of xylan with phenyl chloroformate either in dipolar aprotic solvents with LiCl or in an ionic liquid, XPC with degrees of substitution (DS) of up to 2.0, i.e., fully functionalized derivatives, could be obtained. The synthesis was studied with respect to the influence of different reaction parameters. It was found that the reaction medium as well as the type of starting xylan strongly affected the efficiency of the derivatization. The derivatives obtained were characterized by FT-IR- and NMR spectroscopy. Surprisingly, it was found that C-3 is the most reactive position in this particular reaction while substitution in position C-2 only occurred if the neighboring position C-3 already carried a phenyl carbonate group. XPC were found to form spherical nanoparticles (NP) of well-defined shape with diameters around 158 nm. These materials possess unique potential as activated NP for advanced applications.