Smectic liquid crystals that tilt without layer contraction

在传统的近晶液晶（LC）中，向倾斜的smc相转变伴随着近晶层间距的减小。这对于基于铁电和反铁电密晶LC的电光显示器来说是一个非常不利的因素，因为层压缩导致层在v形几何中屈曲。这将导致此类设备的质量严重下降。最近已经发现了一些几乎没有层压缩的新型近晶材料。这些材料引起了工业界和学术界的极大兴趣；它们似乎代表了一种新型的倾斜转变，这种转变也可以在其他软物质系统中观察到，包括有机单层，人工和生物膜。一种新的SmA - Sm - C跃迁的分子理论将被开发出来，解释为什么有些材料不显示层收缩，而有些材料却显示层收缩，以及分子结构如何影响倾斜跃迁的性质。该理论将解释现有的实验数据，包括低取向顺序和弱层间相关性的作用。基于模型相互作用势，将提出无层压缩的近晶材料的分子模型，并确定分子参数，使人们能够区分传统和新型近晶材料。

In conventional smectic liquid crystals (LC) the transition into thetilted Sm C phase is accompanied by a decrease of smectic layerspacing. This is a very negative factor for electro-optic displaysbased on ferro- and antiferroelectric smectic LC because the layercompression leads to a buckling of layers in a chevron geometry.This results in a serious degrade of the quality of such devices.Recently a number of novel smectic materials have been discoveredwith practically no layer compression. These materials attract asignificant interest from industry and academia; they seem torepresent a novel type of tilting transition which may also beobserved in other soft matter systems including organic monolayers,artificial and biological membranes. A novel molecular theory of SmA - Sm C transition will be developed which explains why somematerials do not show a layer contraction, and why others do, andhow the molecular structure can affect the nature of the tiltingtransition. The theory will explain the existing experimental dataincluding the role of low orientational order and weak interlayercorrelations. Molecular models for smectics without layercompression will be proposed, based on model interaction potentials,and molecular parameters will be identified which enable one todistinguish between conventional and novel smectic materials.