Theoretical Predictions on Normal Stresses under Shear Flow in Transient Networks of Telechelic Associating Polymers
Theoretical Predictions on Normal Stresses under Shear Flow in Transient Networks of Telechelic Associating Polymers
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DOI：
10.1021/ma902191e
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发表时间：
2010-03
期刊：
影响因子：
5.5
通讯作者：
T. Koga;F. Tanaka
中科院分区：
文献类型：
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作者：
T. Koga;F. Tanaka
本文基于瞬态网络理论，研究了定常剪切流作用下遥爪聚合物缔合网络中正应力的行为。我们数值计算表明，第一和第二法向应力系数揭示增厚作为剪切速率的函数，和第二法向应力系数的变化取决于链张力的非线性，从路口的关联组的解离速率，和剪切速率的符号。通过解析计算，我们证明了在小剪切速率的极限下，缔合基团的非线性伸缩与解离之间的竞争导致了符号反转。因此，符号反转的分子机制被证明是类似的剪切粘度的增稠。我们还表明，增厚的第一法向应力系数有一个类似的分子起源。对第一正应力系数的增厚和第二正应力系数的正值进行了理论预测。
This paper studies the behavior of the normal stresses in associated networks composed of telechelic polymers under steady shear flow on the basis of a transient network theory. We numerically show that the first and second normal stress coefficients reveal thickening as a function of shear rate, and that the sign of the second normal stress coefficient changes depending on the nonlinearity in the chain tension, the dissociation rate of the associative groups from junctions, and the shear rate. By analytic calculation, we show that, in the limit of small shear-rate, the sign inversion occurs by the competition between the nonlinear stretching and dissociation of associative groups. Thus, the molecular mechanism of the sign inversion is shown to be similar to that of thickening of the shear viscosity. We also show that thickening of the first normal stress coefficient has a similar molecular origin. The theoretical predictions on thickening of the first normal stress coefficient, and on the positivity of t...