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首页> 外文期刊>Journal of Physics, D. Applied Physics: A Europhysics Journal >Influence of hydrogen bonds on glass transition and dielectric relaxations of cellulose
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Influence of hydrogen bonds on glass transition and dielectric relaxations of cellulose

机译：氢键对纤维素玻璃化转变和介电弛豫的影响

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The molecular dynamics in hydrated cellulose has been investigated by a combination of thermal analyses and dielectric spectroscopy. Differential scanning calorimetry shows the dependence upon hydration of the glass transition temperature T_g. A physical ageing phenomenon has been observed. At the molecular scale, bound water is hydrogen bonded to polar sites of cellulose macromolecules. At the macroscopic scale, water molecules play the role of a plasticizer for cellulose lowering its T_g. Dynamic dielectric spectroscopy combined with thermostimulated currents have allowed us to follow more localized molecular mobility. The ? relaxation mode is characterized by activation entropies that vanish for higher water contents indicating molecular mobility localization. It is plasticized by water like the glass transition. This analogy is explained by a common origin of both mechanisms: the mobility of the cellulose backbone. The evolution of the λ mode upon hydration follows an anti-compensation law. Water acts as an anti-plasticizer in a hydrogen bonded network.
机译：水合纤维素的分子动力学已通过热分析和介电谱的结合进行了研究。差示扫描量热法显示对玻璃化转变温度T_g的水合作用的依赖性。已经观察到物理老化现象。在分子规模上，结合水是氢键合到纤维素大分子的极性位点。在宏观上，水分子起着增塑剂的作用，可降低纤维素的T_g。动态介电谱结合热刺激电流使我们能够追踪更多的局部分子迁移率。 ？弛豫模式的特征在于活化熵对于较高的水含量消失，表明分子迁移率局部化。它像玻璃过渡一样被水塑化。用两种机制的共同来解释这一类比：纤维素骨架的移动性。水合作用时λ模式的演变遵循反补偿定律。水在氢键网络中充当抗增塑剂。

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