A novel and highly efficient polymerization of sulfomethylated alkaline lignins via alkyl chain cross-linking method
2015
Hong, Nanlong | Yu, Wei | Xue, Yuyuan | Zeng, Weimei | Wong, Kim Hoh | Xie, Wenqin | Qiu, Xueqing | Li, Yuan
A new family of water-soluble lignosulfonate polymers with ultrahigh molecular weight (Mw) was developed based on alkali lignin (AL) as starting material in a one-pot reaction in two steps: sulfomethylation of AL as raw material led to AL-S and this material was subsequently cross-linked via alkylation with 1,6-dibromohexane (alkAL-S). Gel permeation chromatography showed a significant increase of Mw from 5200 Da of AL-S to 201 000 Da of alkAL-S with high degree of alkylation. Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance spectroscopy and functional group analysis confirmed the efficient polymerization by a nucleophilic substitution reaction mechanism. Additionally, alkAL-S with high Mw showed unexpected viscosity-reducing effect, stability and good rheological properties on a low-rank coal-water slurry (CWS), which are even better than those obtained by naphthalene sulfonate formaldehyde (NSF) as additive. The adsorption properties of the new products were also characterized via a quartz crystal microbalance combined with dissipation monitoring (QCM-D method). Cross-linked structure, large steric hindrance from high Mw and suitable amphiphilic properties of alkAL-S polymers contribute together to the highly improved dispersion performances for CWS.
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