Glycidyl methacrylate derivatized xylan-rich hemicelluloses: synthesis and characterizations

In this paper, a novel type of hemicellulosic derivative containing polymerizable double bonds (C=C) was synthesized by chemical reaction of xylan-rich hemicelluloses and glycidyl methacrylate (GMA) in dimethyl sulfoxide (DMSO) in presence of catalysts. The chemical structure, reaction mechanism, and rheological properties of the derivative were investigated by means of FT-IR, H-1 and C-13-NMR, DEPT 135 NMR, GC-MS and rheometer. The influence of the reaction conditions including reaction time, temperature, catalysts, and the amount of reagents on the degree of substitution were investigated in detail. Results showed that the chemical reaction of xylan-rich hemicelluloses with GMA was transesterification, which resulted in direct attachment of methacrylate (MA) groups to xylan-rich hemicelluloses, instead of GMA. A maximum degree of substitution of 0.94 could be achieved under the optimum reaction condition (40 A degrees C, 1.8 equiv of GMA to per xylose unit, 36 h, 20 % DMAP). Results from rheological analysis indicated that the aqueous solutions of the methacrylated xylan-rich hemicelluloses (MAXH; 0.5, 1.0 and 2.0 wt%) exhibited typical shear-thinning behavior in the range of shear rates tested. The viscoelasticity of MAXH solutions increased with the increasing concentration and DS.