Novel liquid crystalline structures of a chiral side chain polymer and its phase transitions

L. S. Li, X. J. Hong, S. I. Stupp*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Two novel smectic bilayer structures have been identified in an enantiomerically enriched chiral side chain polymer containing the highly dipolar nitrile group at stereocentres. The structures were characterized by electron diffraction, electron microscopy, and X-ray diffrac­tion. In both phases each smectic layer has a bilayer structure with backbones and spacers confined in a thin disordered region between two sublayers of mesogenic segments. One of the structures which we denote as CrE* has the unusual feature of having its side chains arranged parallel to the layer normal in spite of its enantiomeric bias and twisted nature. In the second structure side chains are tilted by 34 8° with respect to the layer normal and we denote this phase as (formula presented). In both structures each sublayer contains three different orientations of orthorhombic (CrE*) or monoclinic (formula presented) lattices which are related to one another by rotations of ±60° about the c-axis. In both the (formula presented) and the CrE* phases, lattices in each sublayer are regularly rotated about the c-axis by 5-9° relative to those in the adjacent sublayer. The observation of a chiral CrH phase is uncommon and in this specific case the structure is unique since the rotation between adjacent layers occurs about the side- chain axis (c-axis) (formula presented) and not about the layer normal (c*-axis) (CrH*). We believe the system undergoes a change in molecular organization from (formula presented) to CrE* as a result of a chemical reaction which joins a fraction of the stereocentres through covalent bonds. With increasing temperature the CrE* structure was found to transform to a special orthorhombic untwisted smectic phase in which a = 31/2b, denoted here as CrEh. The structure then transforms to a hexatic SB phase and finally to a SA phase at yet higher temperatures.

Original languageEnglish (US)
Pages (from-to)469-483
Number of pages15
JournalLiquid Crystals
Volume21
Issue number4
DOIs
StatePublished - Jan 1 1996

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

Fingerprint Dive into the research topics of 'Novel liquid crystalline structures of a chiral side chain polymer and its phase transitions'. Together they form a unique fingerprint.

Cite this