Paranematic order of nano-confined nCFPB liquid crystals

Spatial confinement on the micro- and nanoscale can markedly affect the physics of liquid crystals (LCs). There is no ‘‘true’’ isotropic-nematic (I-N) transition for LCs confined in geometries spatially restricted in at least one direction to a few nanometres. The anchoring at the confining walls, quantified by a surface field, imposes a partial orientational, that is, a partially nematic ordering of the confined LCs, even at temperatures T far above the bulk I-N transition temperature. The strong first-order I-N transition is replaced by a weak continuous paranematic-nematic (P-N) transition, depending on the strength of the surface orientational field in nanoscopic straight channels in anodic aluminum oxide (AAO) membranes. We propose studies of the self-organization of nCFPB LC molecules in confinement via a series of SANS measurements at thermodynamically characteristic temperatures to provide important structural information for both soft matter theory and practical applications of certain LCs in displays and sensors.

微纳尺度下的空间限域会显著影响液晶（liquid crystals, LCs）的物理特性。当液晶被限域在至少一个方向尺寸仅为数纳米的几何结构中时，不存在"真正的"各向同性-向列相（isotropic-nematic, I-N）转变。由表面场量化的限域壁面锚定作用，即使在远高于本体I-N转变温度的温度T下，也会迫使被限域的液晶产生部分取向，即形成部分向列相序。在阳极氧化铝（anodic aluminum oxide, AAO）膜的纳米直通道中，强烈的一级I-N转变会被微弱的连续预向列相-向列相（paranematic-nematic, P-N）转变所取代，这一过程取决于表面取向场的强度。我们提出通过在热力学特征温度下开展一系列小角中子散射（Small Angle Neutron Scattering, SANS）测量，研究限域环境中nCFPB液晶分子的自组织行为，以期为软物质理论以及特定液晶在显示与传感器领域的实际应用提供重要的结构信息。