Eur. Phys. J. E (2005) 16: 97-107
https://doi.org/10.1140/epje/e2005-00012-3

Regular Articles

Hairpin rubber elasticity

Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge, CB3 0HE, UK

^* e-mail: jma39@hermes.cam.ac.uk

Received: 31 August 2004
Published online: 31 January 2005

Abstract

We model the elastic properties of main chain liquid crystalline elastomers, formed by cross linking chains in a strongly nematic state, when they have hairpin defects. We study the response of the elastomer to imposed uniaxial extension along the nematic direction, and employ a microscopic model of how the deformation is distributed non-affinely amongst the hairpin and straight chain populations. The rubber shows a plateau in the stress as a function of the elongation imposed along the director. It is a consequence of the depletion of the actively stretching population of hairpin chains and should not be confused with soft elasticity effects associated with director rotation.