琼脂凝胶化结构形成过程动力学的新认识
New insight into kinetics behavor of the structural formation process in Agar gelation
摘要：
利用自制的扭转共振器，对凝胶化琼脂水溶液中结构形成过程的动力学和弛豫进行了时间分辨实验研究。该研究基于对琼脂浓度为0.75%、1.0%和2.0% w/w的三种自然冷却溶液的测量。结果表明，根据结构发育速率（SDR）随时间/温度的变化规律，自然冷却琼脂凝胶化过程可分为溶胶阶段（第一阶段）、凝胶区阶段（第二阶段）和凝胶阶段（第三阶段）。在第二阶段和第三阶段观察到SDR的一个有趣的波动衰减行为，表明多重弛豫过程的总和，并通过一个多阶类高斯方程很好地描述：更有趣的是，在第二阶段和第三阶段的Wn拟合值的温度依赖性被发现遵循不同的Arkenius定律，具有不同的活化能EaII= 39-74 KJ/mol和EaIII~7.0 KJ/mol。这两种不同的类Arrhenius行为分别表明，第二阶段的分散体是由于琼脂分子自组装的松弛或凝胶化过程中连接区的生长，其中氢键相互作用的形成或分裂起着重要作用;并且第III阶段中的分散体归因于从各种尺寸域释放的水的松弛动力学，所述尺寸域接近于脱水收缩过程中的水。
英文摘要：
A time-resolved experimental study on the kinetics and relaxation of the structural formation process in gelling Agar-water solutions was carried out using our custom-built torsion resonator. The study was based on measurements of three naturally cooled solutions with agar concentrations of 0.75%, 1.0% and 2.0% w/w. It was found that the natural-cooling agar gelation process could be divided into three stages, sol stage (Stage I), gelation zone (Stage II) and gel stage (Stage III), based on the time/temperature evolutions of the structural development rate (SDR). An interesting fluctuant decaying behavior of SDR was observed in Stage II and III, indicative of a sum of multiple relaxation processes and well described by a multiple-order Gaussisn-like equation: . More interestingly, the temperature dependences of the fitted values of Wn in Stage II and Stage III were found to follow the different Arrhenius laws, with different activation energies of EaII= 39-74 KJ/mol and EaIII~7.0 KJ/mol. The two different Arrhenius-like behaviors respectively suggest that dispersions in Stage II be attributed to the relaxation of the self-assembly of agar molecules or the growth of junction zones en route to gelation, in which the formation or fission of hydrogen bonding interactions plays an important role; and that dispersions in Stage III be attributed to the relaxation dynamics of water released from various size domains close to the domain of the viscous flow of water during the syneresis process.
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