Department of Polymer Science and Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, People's Republic of China.
J Chem Phys. 2012 Feb 21;136(7):074902. doi: 10.1063/1.3685220.
In this study, we apply a self-consistent field theory of polymers to study the structures of a symmetric diblock copolymer in parallel substrates filled with square-pillar arrays in which the substrates and pillars exhibit a weak preference for one block of the copolymer. Three classes of structures, i.e., lamellae, perpendicular cylinders, and bicontinuous structures, are achieved by varying the polymer film thickness, the pillar pitch (the distance between two centers of the nearest neighboring pillars), the gap and rotation of the pillars. Because of the confinement along horizontal directions imposed by the pillar array, eight novel types of perpendicular lamellar structures and eight novel types of cylindrical structures with various shapes and distributions occur. In the hybridization states of the parallel and perpendicular lamellar structures, several novel bicontinuous structures such as the double-cylinder network, pseudo-lamellae, and perforated lamellar structure are also found. By comparing the free energies of the various possible structures, the antisymmetric parallel lamellae are observed to be stable with the larger pillar gap at a certain film thickness. The structural transformations between the alternating cylindrical structures (alternating cross-shaped, square-shaped, and octagonal perpendicular cylinders) and parallel lamellae with increasing film thickness or pillar gap are well explained by the modified strong separation theory. Our results indicate that array confinement can be an effective method to prepare novel polymeric nanopattern structures.
在这项研究中，我们应用聚合物的自洽场理论来研究对称两嵌段共聚物在填充有正方形柱状阵列的平行基底中的结构，其中基底和柱状物对共聚物的某一嵌段表现出微弱的偏好。通过改变聚合物膜的厚度、柱状物的间距（最近邻柱状物中心之间的距离）、间隙和柱状物的旋转，可以实现三种结构，即层状结构、垂直圆柱结构和双连续结构。由于柱状物阵列沿水平方向的限制，出现了八种新型的垂直层状结构和八种具有各种形状和分布的新型圆柱结构。在平行和垂直层状结构的杂交状态下，还发现了几种新型的双连续结构，如双圆柱网络、拟层状结构和穿孔层状结构。通过比较各种可能结构的自由能，发现具有较大柱状物间隙的非对称平行层状结构在一定膜厚下是稳定的。随着膜厚或柱状物间隙的增加，交替圆柱结构（交替十字形、方形和八角形垂直圆柱）和平行层状结构之间的结构转变可以通过改进的强分离理论很好地解释。我们的结果表明，阵列限制可以成为制备新型聚合物纳米图案结构的有效方法。
