Nonlinear Branch-Point Dynamics of Multiarm Polystyrene
Nonlinear Branch-Point Dynamics of Multiarm Polystyrene
复制标题
多臂聚苯乙烯的非线性分支点动力学
DOI：
10.1021/ma061476r
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发表时间：
2006
期刊：
影响因子：
5.5
通讯作者：
O. Hassager
中科院分区：
文献类型：
--
作者：
J. Nielsen;H. K. Rasmussen;M. Denberg;K. Almdal;O. Hassager
合成了两种具有窄摩尔质量分布的支化聚苯乙烯熔体：多臂An-C-C-Anpom-pom聚苯乙烯和An-C不对称星星聚苯乙烯，其中n是臂数。pom-pom和不对称星星的摩尔质量分别为Mw = 300 kg/mol和Mw = 275 kg/mol。据估计，pom-pom平均有2.5个臂，而非对称星星的估计是3.3个。每个臂的摩尔质量为约27 kg/mol。熔体的特征在于在线性粘弹性制度和拉伸流变仪在非线性制度。对于不对称的星星聚苯乙烯，测得的瞬态拉伸粘度是不一致的流变本构方程，是可分离的时间和应变。然而，与这种情况相反，对于pom-pom聚苯乙烯，瞬时拉伸粘度可以通过时间-应变可分离的本构方程来描述，其伸长率大于逆蠕动时间。到2.6的Hencky菌株，C.
Two branched polystyrene melts with narrow molar mass distribution have been synthesized: a multiarm An−C−C−An pom-pom polystyrene and an An−C asymmetric star polystyrene where n is the number of arms. The pom-pom and the asymmetric star have molar masses of Mw = 300 kg/mol and Mw = 275 kg/mol, respectively. The pom-pom was estimated to have 2.5 arms on average, while the estimate is 3.3 for the asymmetric star. The molar mass of each arm is about 27 kg/mol. The melts were characterized in the linear viscoelastic regime and by elongational rheometry in the nonlinear regime. For asymmetric star polystyrene, the measured transient elongational viscosity is not consistent with a rheological constitutive equation that is separable in time and strain. Contrary to this situation, however, for pom-pom polystyrene, the transient elongational viscosity may be described by a time−strain separable constitutive equation for elongation rates larger than the inverse reptation time. Up to a Hencky strains of 2.6, the c...