Smectic liquid crystals that tilt without layer contraction

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.