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 chainsEvgeniy 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)
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 (where and are the dimensions perpendicular and parallel to the nematic axis, respectively). Values of the rotational relaxation time of the polymer chains are also obtained.
61.30G - 61.40K - 62.10
© Les Editions de Physique 1992