DYNAMIC VISCOELASTIC MODULUS OF ASSOCIATIVE POLYMER NETWORKS - OFF-LATTICE SIMULATIONS, THEORY AND COMPARISON TO EXPERIMENTS
DYNAMIC VISCOELASTIC MODULUS OF ASSOCIATIVE POLYMER NETWORKS - OFF-LATTICE SIMULATIONS, THEORY AND COMPARISON TO EXPERIMENTS
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DOI：
10.1021/ma00122a041
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发表时间：
1995-08-28
期刊：
影响因子：
5.5
通讯作者：
AGTEROF, WGM
中科院分区：
文献类型：
--
作者：
GROOT, RD;AGTEROF, WGM
最近引入的缔合聚合物凝胶的离格模拟模型（Groot, R. D.; Agterof, W. G. M. J. Chem. Phys. 1994, 100, 1649）已被应用于获得作为频率和聚合物浓度的函数的机械谱，使用时间相关模量的 Green-Kubo 关系。在我们的模拟中可以观察到两个放松阶段。早期衰减符合-2/3幂律，其形式对聚合物浓度、缔合寿命和缔合度的大变化不敏感。后期像劳斯模型中的端到端矢量一样松弛，具有与浓度的立方成比例的特征应力和与单体-单体解离速率成正比的松弛时间。模拟结果与文献中针对几种物理凝胶的实验进行了比较。这种定量一致性对涉及流体动力相互作用或蠕动的其他假设机制提出了质疑，因为模拟不包含这些特征。作为观察到的早期衰减的另一种解释，给出了幂律指数和聚合物分形维数之间的明确关系。
An off-lattice simulation model for associative polymer gels as introduced recently (Groot, R. D.; Agterof, W. G. M. J. Chem. Phys. 1994, 100, 1649) has been applied to obtain the mechanical spectrum as a function of frequency and polymer concentration, using a Green-Kubo relation for the time-dependent modulus. Two stages of relaxation are observable in our simulations. The early-time decay is consistent with a -2/3 power law, whose form is insensitive to large variations in polymer concentration, association lifetime, and degree of association. The late stage, which relaxes like the end-to-end vector in the Rouse model, has a characteristic stress that scales as the cube of the concentration and a relaxation time that is proportional to the monomer-monomer dissociation rate. The simulation results have been compared with experiments found in the literature for several physical gels. The quantitative agreement calls into question other postulated mechanisms involving hydrodynamic interaction or reptation, since the simulation contains neither of these features. As an alternative explanation for the observed early-time decay, an explicit relation between the power law exponent and the polymer fractal dimension is given.