Department of Polymer Science and Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA.
J Chem Phys. 2012 Sep 14;137(10):104911. doi: 10.1063/1.4752198.
We study the phase behavior of diblock copolymer melts with one block possessing orientation-dependent segmental interactions using self-consistent field theory. A generalized coarse-grained description is introduced based on the local (polar) orientational order parameter and K, an effective Frank elastic constant for orientational gradients. To explore the role played by orientational interactions in assembly thermodynamics, we apply the theory to two-dimensional melt morphologies for a range of K. As microphase segregation necessarily introduces splay deformations of the segment orientation, we find that increasing the stiffness K raises the critical χN at the onset of microphase separation. Furthermore, we find that strong orientational interactions in one block give rise to highly asymmetric phase diagrams due to the large penalty for high-splay morphologies, such as the cylindrical phase. Finally, we analyze the costs of inter-segmental splay as well as the size dependence of domain spacing on K based on a strong-segregation picture of morphologies.
我们使用自洽场理论研究了具有一个具有取向相关的分段相互作用的嵌段共聚物熔体的相行为。基于局部（极性）各向异性取向有序参数和 K（用于取向梯度的有效弗兰克弹性常数），引入了广义的粗粒化描述。为了探索取向相互作用在组装热力学中的作用，我们将理论应用于 K 范围内的二维熔体形态。由于微相分离必然会引入分段取向的展曲变形，我们发现增加刚度 K 会提高微相分离开始时的临界 χN。此外，我们发现一个嵌段中的强取向相互作用会由于高展曲形态（例如圆柱相）的高代价而导致高度不对称的相图。最后，我们根据形态的强分离图像分析了段间展曲的代价以及域间距对 K 的尺寸依赖性。
