Temperature dependences of the twist viscosity coefficient for solutions of comb-like mesogenic polymer in a nematic solvent : estimation of the anisotropy and rotational relaxation time of chains

Evgeniy E. Pashkovsky; Tamara G. Litvina; Sergei G. Kostromin; Valery P. Shibaev

doi:doi:10.1051/jp2:1992223

Numéro		J. Phys. II France Volume 2, Numéro 8, August 1992


Page(s)		1577 - 1587
DOI		https://doi.org/10.1051/jp2:1992223

DOI: 10.1051/jp2:1992223
J. Phys. II France 2 (1992) 1577-1587

Temperature dependences of the twist viscosity coefficient for solutions of comb-like mesogenic polymer in a nematic solvent : estimation of the anisotropy and rotational relaxation time of chains

Evgeniy E. Pashkovsky¹, Tamara G. Litvina¹, Sergei G. Kostromin² and Valery P. Shibaev²

¹ Institute of Macromolecular Compounds of the Russian Academy of Sciences, Bolshoi 31, St.-Petersburg, 199004, Russia
² Chemical Department, Moscow State University, Leninskye Gory, Moskow, 119899, Russia

(Received and revised 28 April 1992, accepted 4 May 1992)

Abstract
The dynamic of Freederiks transition at bend deformation is used to study the viscoelastic properties of dilute solutions for three fractions of the side-chain mesogenic polyacrylate in the nematic solvent, pentylcyanobiphenyl (5CB). Values of the bend elastic constant K₃ for polymer solutions are higher than for pure 5CB, especially for solutions of fractions with a relatively high degree of polymerization. The strong effect of polymer molecules on twist viscosity is also observed, but this effect has only a slight dependence on the degree of polymerization. Analysis of obtained experimental data based on the Brochard theory gives the values of the anisotropy of chain dimensions $R_{\perp}/R_{\parallel}$ (where $R_{\perp}$ and $R_{\parallel}$ are the dimensions perpendicular and parallel to the nematic axis, respectively). Values of the rotational relaxation time of the polymer chains are also obtained.