Structure and Properties of New de Vries SmA* Liquid Crystals

Abstract

We synthesized a chiral mesogen AC11 and two different siloxanes MSi2-AC11 and DSi3-AC11 derived from it by a hydrosilylation reaction. The effects of varying the molecular architecture were investigated with special attention being devoted to the occurrence of the de Vries SmA* phase. Strong hints that all the three molecules follow the scenario suggested by de Vries were found in the behavior of the susceptibility by studies of their electrooptical response in the SmA* phase. In particular, DSi3-AC11 containing two mesogens interconnected by a siloxane spacer presented a critical exponent γ as high as 1.97, indicating a practically pure de Vries behavior. Temperature-dependent X-ray analysis revealed that the three materials underwent a small layer shrinkage at the SmA*–SmC* transition.

Keywords:

• de Vries
• electrooptics
• phase structure
• siloxane liquid crystal
• smectic A

Acknowledgement

This work was supported by the EU Contract HPRN-CT-2002-00202 SAMPA.