Issue 6, 2009

Siloxanes and carbosilanes as new building blocks for T-shaped bolaamphiphilic LC molecules

Abstract

T-shaped bolaamphiphiles composed of a 4,4′-disubstituted biphenyl core and terminal diol groups with laterally attached oligo(siloxane) and carbosilane units were synthesized and investigated with respect to their self-assembly into liquid crystalline superstructures (thermotropic mesophases). Two different types of bolaamphiphiles were investigated: one has two identical glycerol groups at both ends of the biphenyl core, which are connected by ether linkages and in the other type one of the ether linkages is replaced by an amide group. The position of the lateral groups on the biphenyl core was also varied. In addition to these silylated compounds two different types of n-alkyl substituted compounds were investigated and compared with the silylated bolaamphiphiles. A hexagonal cylinder phase and three distinct types of lamellar phases were observed and a phase sequence Colhex–LamSm–LamN–LamIso was found by increasing the size of the lateral substituent. The silyl units organize into distinct compartments either within columns or between layers. The increased flexibility of the silyl units compared to linear alkyl chains and perfluorinated chains leads to materials with phase transitions in convenient temperature ranges. For one of the carbosilanes an unusually broad region of the LamN phase was achieved. It turned out that an additional amide group leads to a significant mesophase destabilization which is attributed to a competition between intramolecular and intermolecular hydrogen bonding. The position of the lateral chain is also important, as it influences hydrogen bonding as well as the conformation of the biphenyl unit.

Graphical abstract: Siloxanes and carbosilanes as new building blocks for T-shaped bolaamphiphilic LC molecules

Supplementary files

Article information

Article type
Paper
Submitted
24 Oct 2008
Accepted
24 Dec 2008
First published
11 Feb 2009

Soft Matter, 2009,5, 1214-1227

Siloxanes and carbosilanes as new building blocks for T-shaped bolaamphiphilic LC molecules

R. Kieffer, M. Prehm, K. Pelz, U. Baumeister, F. Liu, H. Hahn, H. Lang, G. Ungar and C. Tschierske, Soft Matter, 2009, 5, 1214 DOI: 10.1039/B818871H

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements