NEMATIC ELASTOMERS - A NEW STATE OF MATTER

Recent experimental and theoretical work shows that nematic elastomers have a highly mobile director, despite being nominally solid liquid c rystals. We review this work and show that such a system represents an essentially new state of matter with non-symmetric elasticity, new ne matic transitions, discontinuous stress-strain relations and an abilit y to behave like liquids for some special class of deformations. These phenomena have been seen in large monodomain samples made in nematic fields or by multistage crosslinking under stresses. Modelling of mono domain elastomers is straightforward and successfully explains the unu sual mechanical behaviour observed. The theory is a direct extension o f the classical theory of conventional rubbers; we call it the neo-cla ssical theory of elastomers. Being a molecular theory, it describes th e very large extensions at which the new transitions occur. We outline problems for the future, principally those of polydomains. Copyright (C) 1996 Elsevier Science Ltd.