Europhys. Lett.
Volume 63, Number 1, July 2003
Page(s) 76 - 82
Section Condensed matter: structure, mechanical and thermal properties
Published online 01 June 2003
DOI: 10.1209/epl/i2003-00480-8
Europhys. Lett., 63 (1) , pp. 76-82 (2003)

Phase transitions of nematic rubbers

P.-G. de Gennes1 and K. Okumura1, 2

1  Laboratoire de Physique de la Matière Condensée, Collège de France 75231 Paris Cedex 05, France
2  Department of Physics, Graduate School of Humanities and Sciences Ochanomizu University - 2-1-1, Otsuka, Bunkyo-ku, Tokyo 112-8610, Japan

(Received 17 March 2003; accepted in final form 2 May 2003)

Single-crystal nematic elastomers undergo a transition from a strongly ordered phase N to an "isotropic" phase I. We show that: a) samples produced under tension by the Finkelmann procedure are intrinsically anisotropic and should show a small (temperature-dependent) birefringence in the high-temperature I phase; b) for the $I\rightarrow N$ transition via cooling there is a spinodal limit but for the $N\rightarrow I$ transition via heating there is no soft mode at the standard spinodal temperature; c) the $N\rightarrow I$ transition is reminiscent of a martensitic transformation: nucleation of the I phase should occur in the form of platelets, making a well-defined angle with the director.

64.70.Md - Transitions in liquid crystals.
64.60.Qb - Nucleation.
61.30.Vx - Polymer liquid crystals.

© EDP Sciences 2003