Viscoelasticity and extensional rheology of model Cayley-tree polymers of different generations
Viscoelasticity and extensional rheology of model Cayley-tree polymers of different generations
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DOI：
10.1122/1.3368724
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发表时间：
2010-05
影响因子：
3.3
通讯作者：
E. Ruymbeke;E. B. Muliawan;S. Hatzikiriakos;T. Watanabe;A. Hirao;D. Vlassopoulos
中科院分区：
文献类型：
--
作者：
E. Ruymbeke;E. B. Muliawan;S. Hatzikiriakos;T. Watanabe;A. Hirao;D. Vlassopoulos
我们研究了一系列阴离子合成的，模型对称凯莱树聚（甲基丙烯酸甲酯）具有从1到4代相同的摩尔质量的流变学。通过考虑平台模量和特征弛豫时间，从线性数据评估不同代的分级弛豫。采用基于运动层次概念的管模型时间推进分析方法，定量描述了不含可调参数的频谱。我们还使用Sentmanat拉伸流变仪夹具进行单轴拉伸测量。在较低和中等Hencky应变速率下，测试的样品与其线性类似物相比表现出显著的应变硬化。随着世代数的增加，这种硬化更加明显，因此出现了分支点。提取的有效稳定拉伸粘度被发现与拉伸速率成比例，幂指数约为-0.5，与线性聚苯乙烯的早期研究结果一致。我们还扩展了时间推进算法来预测这些聚合物的拉伸行为使用的概念框架最近开发的pom-pom和凯莱树聚合物。理论和实验结果之间的比较是令人满意的最大拉伸时，可以支持的分子估计占最近提出的链间压力的影响。(C)2010流变学学会。[DOI 10.1122/1.3368724]
We investigated the rheology of a series of anionically synthesized, model symmetric Cayley tree poly(methylmethacrylates) having from 1 to 4 generations of identical molar mass. The hierarchical relaxation of the different generations was assessed from the linear data by accounting for both the plateau modulus and the characteristic relaxation times. Using a tube-model time-marching analysis based on the concept of hierarchy of motion, we described quantitatively the frequency spectra without adjustable parameters. We also performed uniaxial extensional measurements using the Sentmanat extensional rheometer fixture. The samples tested exhibited significant strain hardening compared to their linear analogs at lower and intermediate Hencky strain rates. This hardening was more pronounced with increasing number of generations, hence branch points. The extracted effective steady extensional viscosity was found to scale with the extensional rate with a power exponent of about -0.5, in agreement with earlier findings with linear polystyrenes. We also extended the time-marching-algorithm to predict the extensional behavior of these polymers using the conceptual framework developed recently for pom-pom and Cayley-tree polymers. Comparison between theoretical and experimental results was satisfactory when the maximum stretch which can be supported by the molecule was estimated by accounting for the recently proposed inter-chain pressure effects. (C) 2010 The Society of Rheology. [DOI: 10.1122/1.3368724]