Effects of fluctuations of cross-linking points on viscoelastic properties of associating polymer networks
Effects of fluctuations of cross-linking points on viscoelastic properties of associating polymer networks
复制标题
交联点波动对缔合聚合物网络粘弹性的影响
DOI：
10.1007/s00397-012-0656-4
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发表时间：
2012
期刊：
影响因子：
2.3
通讯作者：
J. Takimoto
中科院分区：
文献类型：
--
作者：
T. Indei;J. Schieber;J. Takimoto
在单链方法的基础上，我们研究了交联点或结的波动对多黏贴缔合聚合物形成的聚合物网络的动态力学和粘弹性性能的影响。通过引入虚拟弹簧来实现结点的波动。我们考虑了处理虚拟弹簧的两种可能情况：虚拟弹簧的直接贡献要么被忽略，要么被包括在应力中。我们表明，如果忽略，结的波动降低（或软化）动态模量在很宽的频率范围内。这一结果与几种预测静态或平台模量下降的多链模型的结果在质量上一致。我们还表明，波动加速了低频下由黏贴的联想/分离过程产生的联想劳斯模式。这些结果显然是合理的，但预计由于忽略了总应力对虚弹簧的贡献而违反虚功原理和热力学第二定律，因此热力学不一致性会产生一些误差。另一方面，如果应力中包含虚拟弹簧的直接贡献，则热力学满足，但平台模量不变，与多链预测相反。软化只发生在低频区。因此，每种方法都有优点和缺点，因此在单链方法的框架下处理结波动需要谨慎和进一步的研究。
We study the effects of fluctuations of cross-linking points, or junctions, on the dynamic mechanical and viscoelastic properties of polymer networks formed by multisticker associating polymers on the basis of a single-chain approach. Fluctuations of junctions are implemented by introducing virtual springs. We consider two possible cases for the treatment of virtual springs: the direct contribution from virtual springs is either neglected or included in the stress. We show that, if neglected, the fluctuation of junctions decreases (or softens) the dynamic modulus over a wide range of frequencies. This result agrees qualitatively with the result of several multichain models that predicts the decrease of the static or plateau modulus. We also show that the fluctuation accelerates the associative Rouse mode at low frequencies originating from the association/dissociation process of stickers. These results are apparently reasonable, but it is expected that there are some errors arising from thermodynamical inconsistency due to the neglect of virtual-spring contribution from the total stress against the virtual work principle and the second law of thermodynamics. On the other hand, if the direct contribution from the virtual springs is included in the stress, thermodynamics is satisfied but the plateau modulus does not change, contrary to the multichain prediction. The softening occurs only at the low-frequency regime. Thus, each method has both merits and demerits, and hence the treatment of junction fluctuations in the framework of single-chain approaches requires care and further investigation.