Rheological properties and conformation of a side-chain liquid crystal polysiloxane dissolved in a nematic solvent

Yiqiang Zhao, Shaosheng Dong, Alex M. Jamieson*, Xuesong Hu, Jyotsana Lal, Sergei Nazarenko, Stuart J. Rowan

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)


We report measurements of the change in electrorheological response of the low molar mass nematic pentylcyanobiphenyl (5CB) on dissolution of small amounts of a side-chain liquid crystal polymer (SCLCP). From the ratio of the intrinsic viscosities with the field on and off, [η on] and [η off], respectively, we deduce a value for the ratio of the rms end-to-end distances of the SCLCP parallel and perpendicular to the nematic director, R par;/R = 1.17 ± 0.02 via application of the Brochard hydrodynamic model, which indicates that the polymer has a slightly prolate shape. Small-angle neutron scattering measurements reveal a numerically similar value for the corresponding ratio of apparent rms radii of gyration, R g∥R g⊥ = 1.12 ± 0.06, for the SCLCP dissolved in deuterated 5CB. Observations of the shear stress transient response of a homeotropic monodomain indicate that, at a concentration between 0.01 and 0.02 g/mL, the solution exhibits a transition from director-aligning to director-tumbling behavior. This result is inconsistent with the Brochard model, which predicts such a transition only for a polymer with an oblate shape but agrees with a modified version, which assumes an additional contribution to viscous stress arises due to elastic coupling between the solvent and polymer directors.

Original languageEnglish
Pages (from-to)5205-5213
Number of pages9
Issue number12
Publication statusPublished - 2005 Jun 14
Externally publishedYes

ASJC Scopus subject areas

  • Materials Chemistry


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