Microstructure and aggregation behavior of methylcelluloses prepared in NaOH/urea aqueous solutions

详细信息    查看全文

• 作者：Jinping Zhou ; Yanli Xu ; Xiaolu Wang ; Ye Qin ; Lina Zhang
• 关键词：Methylcellulose ; Microstructure ; Aggregation ; Molecular weight ; Light scattering
• 刊名：Carbohydrate Polymers
• 出版年：2008
• 出版时间：21 November 2008
• 年：2008
• 卷：74
• 期：4
• 页码：901-906
• 全文大小：370 K

文摘

Three water-soluble methylcelluloses (MCs) were prepared through homogeneous reaction in NaOH/urea aqueous solution, using dimethyl sulfate as a methylation reagent. The microstructure of the MC samples was characterized by IR, GC/MS, NMR, while dilute solution properties were measured by SEC–LLS, DLS and viscometer. The total degrees of substitution (DS) of the MC samples were 1.09, 1.42 and 1.56, respectively. However, we found that the relative DS value varies with the position of the hydroxyl group, i.e., C-2 > C-3 ≈ C-6, indicating the difference of reaction activity of different hydroxyl groups. In aqueous solution, MC has a trendency to form aggregates and hard to form actual solution, even at low concentration and low temperature, which was confirmed by the SEC–LLS and DLS result that isolated MC chains and large aggregates coexisted in the dilute aqueous solution. MC aqueous solutions showed two-stage temperature dependence of hydrodynamic radius. In the first stage, i.e., the temperature ranges from 20 to 65 °C, the hydrodynamic radius of MC displayed bimodal distribution, corresponding to the single chains and large aggregates. While in the second stage, i.e., the temperature higher than 70 °C, only large aggregates appeared. The results also proved that the microstructure of MC had a great influence on its physical properties.