Zhang Zunmin, Guo Hongxia, Nies Erik
Beijing National Laboratory for Molecular Sciences, Joint Laboratory of Polymer Sciences and Materials, State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences Beijing 100190 China
Division of Polymer Chemistry and Materials, Department of Chemistry, KU Leuven Celestijnenlaan 200F B-3001 Heverlee Belgium
RSC Adv. 2018 Dec 18;8(73):42060-42067. doi: 10.1039/c8ra09490j. eCollection 2018 Dec 12.
Dissipative particle dynamics simulations have been applied to study the temperature dependent anchoring and wetting behavior of thermotropic liquid crystals (LCs) in the presence of a rod-coil amphiphilic monolayer at the aqueous-LC interface. Upon cooling in the nematic phase, a thermally-induced anchoring transition from homeotropic through tilted to planar has been observed. The growth and propagation of smectic order from the interfaces to the bulk nematic LCs are demonstrated to be mainly responsible for this novel transition sequence. In particular, when a complete smectic layer in the amphiphile monolayer is induced around the bulk transition of nematic-smectic-A, the propagation of homeotropic alignment fails instantly and a unique planar anchoring configuration is formed instead. While heating towards the isotropic phase, simulation results show that the nematic-isotropic transition of confined LCs is slightly shifted to a higher temperature, and a nematic wetting layer with homeotropic alignment appears in the rod block monolayer when the bulk LCs is isotropic. Our systematic simulations throughout the whole phase regimes of LCs provide important molecular-level insight into how the coupling between the ordering of LCs and adsorbents and their temperature dependencies affect the anchoring behavior in this complex system, which should be instrumental in the rational design and application of advanced LC-based biosensors with optimal operating temperature range.
耗散粒子动力学模拟已被用于研究热致液晶（LCs）在水-LC界面存在棒-线圈两亲单层时的温度依赖性锚定和润湿行为。在向列相冷却过程中，观察到了从垂直取向通过倾斜取向到平面取向的热诱导锚定转变。从界面到体相向列型液晶的近晶有序的生长和传播被证明是这种新颖转变序列的主要原因。特别是，当在向列-近晶-A体相转变附近诱导两亲单层中形成完整的近晶层时，垂直取向的传播立即失效，取而代之的是形成独特的平面锚定构型。在向各向同性相加热时，模拟结果表明，受限液晶的向列-各向同性转变略微向较高温度偏移，并且当体相液晶为各向同性时，在棒状嵌段单层中出现垂直取向的向列润湿层。我们在液晶的整个相区进行的系统模拟为液晶和吸附剂的有序性及其温度依赖性之间的耦合如何影响这个复杂系统中的锚定行为提供了重要的分子水平见解，这对于合理设计和应用具有最佳工作温度范围的先进液晶基生物传感器应该是有帮助的。
