California State University, Sacramento, 6000 J Street, Sacramento, California 95819, USA.
Université de Picardie Jules Verne, 80039 Amiens, France.
Phys Rev E. 2017 May;95(5-1):052706. doi: 10.1103/PhysRevE.95.052706. Epub 2017 May 31.
We measured the Rapini-Papoular polar anchoring strength coefficient W for 4^{'}-pentyl-4-cyanobiphenyl (5CB) on alignment layers formed by the reactive mesogen photopolymers RM 257, RM 82, and RM 84 [4,4^{'}-bis(acryloyl)biphenyl] (by Merck). These materials are commonly used for the photostabilization of the liquid crystal (LC) director in the bulk as well as at the surface of the LC layer via the formation of a loose polymer network that captures the director orientation. We developed a method of fabrication of alignment layers from these polymers, and estimated W from the measurements of the optical retardation as a function of applied voltage in uniformly aligned cells. We found that RM 257 yielded W of about 6×10^{-4}J/m^{2}, whereas RM 82 and RM 84 provided anchoring strengths of about 2×10^{-4} and 4×10^{-4}J/m^{2}, respectively. Subsequent heating of the sample either destroyed the alignment layer, or substantially decreased W to about 1×10^{-4}J/m^{2}, which was comparable to the anchoring strength of weakly rubbed commercial polyimides.
我们测量了反应性介晶光聚合物 RM 257、RM 82 和 RM 84 [4,4'-双（丙烯酰基）联苯]（默克公司）形成的取向层上 4'-戊基-4-氰基联苯（5CB）的拉皮尼-帕波ular 极向锚定强度系数 W。这些材料通常用于通过形成松散的聚合物网络来稳定液晶（LC）的指向矢，该聚合物网络捕获指向矢的方向，从而在 LC 层的体相和表面稳定 LC 的指向矢。我们开发了一种从这些聚合物制备取向层的方法，并通过在均匀取向的单元中测量光学延迟与施加电压的函数关系来估计 W。我们发现 RM 257 的 W 值约为 6×10^{-4}J/m^{2}，而 RM 82 和 RM 84 的 W 值分别约为 2×10^{-4}和 4×10^{-4}J/m^{2}。随后对样品进行加热，要么破坏了取向层，要么使 W 显著降低至约 1×10^{-4}J/m^{2}，这与弱摩擦商用聚酰亚胺的锚定强度相当。
