The present study investigates rheological properties of microphase-separated lamellar structures formed by unentangled and weakly entangled diblock copolymer melts under a finite amplitude oscillatory shear flow and a steady shear flow. To simulate such a system, dissipative particle dynamics (DPD) simulation is employed to reproduce the lamellar structures, where a multi-chain slip-spring model is combined with DPD simulation to mimic entanglement effects. By imposing an oscillatory shear flow, this model enables us to measure storage and loss moduli for three different (parallel, perpendicular, and transverse) lamellar orientations with respect to the flow direction. These orientations display distinctive rheological behaviors, and especially the transverse orientation exhibits a peculiar behavior owing to a finite expansion of the lamellar interfaces, which differs from a previous study. In a steady shear flow, steady shear viscosities of parallel and perpendicular orientations are evaluated. In this case, the orientations of lamellar domains and the local orientation and stretching of bonds near the lamellar interfaces affect the steady shear viscosities. A spatial distribution of entanglements also affects the steady shear viscosities differently from another previous study.

中文翻译：

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形成薄片的二嵌段共聚物的流变特性

本研究调查了由未缠结和弱缠结的二嵌段共聚物熔体在有限振幅振荡剪切流和稳定剪切流下形成的微相分离层状结构的流变特性。为了模拟这样的系统，采用耗散粒子动力学 (DPD) 模拟来重现层状结构，其中多链滑动弹簧模型与 DPD 模拟相结合以模拟纠缠效应。通过施加振荡剪切流，该模型使我们能够测量相对于流动方向的三种不同（平行、垂直和横向）层状取向的存储和损失模量。这些取向显示出独特的流变行为，特别是由于层状界面的有限扩展，横向取向表现出一种特殊的行为，这与之前的研究不同。在稳定剪切流中，评估平行和垂直方向的稳定剪切粘度。在这种情况下，层状域的取向和层状界面附近的局部取向和键的拉伸会影响稳态剪切粘度。缠结的空间分布也与之前的另一项研究不同地影响稳定剪切粘度。层状畴的取向和层状界面附近的局部取向和键的拉伸影响稳态剪切粘度。缠结的空间分布也与之前的另一项研究不同地影响稳定剪切粘度。层状域的取向和层状界面附近的局部取向和键的拉伸影响稳态剪切粘度。缠结的空间分布也与之前的另一项研究不同地影响稳定剪切粘度。