Deduction of the temperature-dependent structure of the four-layer intermediate smectic phase using resonant X-ray scattering

• Published in: The European physical journal. E, Soft matter and biological physics Vol. 23; no. 3; pp. 281 - 287
• Main Authors: BRIMICOMBE, P. D, ROBERTS, N. W, JARADAT, S, SOUTHERN, C, WANG, S.-T, HUANG, C.-C, DIMASI, E, PINDAK, R, GLEESON, H. F
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 01.07.2007
• Subjects: Complex Mixtures - chemistry; Computer Simulation; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Liquid crystals; Liquid Crystals - chemistry; Models, Chemical; Phase Transition; Physics; Selenium - chemistry; Structure of solids and liquids; crystallography; Temperature; X-Ray Diffraction - methods; X-ray scattering; Resonance scattering; Smectic crystals; Phase transformations; Temperature effects; Chirality; Doping; Binary mixtures; Antiferroelectric liquid crystals; Structural analysis
• ISSN: 1292-8941; 1292-895X
• DOI: 10.1140/epje/i2007-10189-0

A binary mixture of an antiferroelectric liquid-crystal material containing a selenium atom and a highly chiral dopant is investigated using resonant X-ray scattering. This mixture exhibits a remarkably wide four-layer intermediate smectic phase, the structure of which is investigated over a temperature range of 16K. Analysis of the resonant X-ray scattering data allows accurate measurement of both the helicoidal pitch and the distortion angle as a function of temperature. The former decreases rapidly as the SmC* phase is approached, whilst the latter remains constant over the temperature range studied at 8 degrees +/-3 degrees. We also observe that the senses of the helicoidal pitch and the unit cell of the repeating four-layer structure are opposite in this mixture and that there is no pitch inversion over the temperature range studied.