120 research outputs found
Isotropic-Cholesteric Transition of a Weakly Chiral Elastomer Cylinder
When a chiral isotropic elastomer is brought to low temperature cholesteric
phase, the nematic degree of freedom tends to order and form a helix. Due to
the nemato-elastic coupling, this also leads to elastic deformation of the
polymer network that is locally coaxial with the nematic order. However, the
helical structure of nematic order is incompatible with the energetically
preferred elastic deformation. The system is therefore frustrated and
appropriate compromise has to be achieved between the nematic ordering and the
elastic deformation. For a strongly chiral elastomer whose pitch is much
smaller than the system size, this problem has been studied by Pelcotivs and
Meyer, as well as by Warner. In this work, we study the isotropic-cholesteric
transition in the weak chirality limit, where the pitch is comparable or much
larger than system size. We compare two possible solutions: a helical state as
well as a double twist state. We find that the double twist state very
efficiently minimizes both the elastic free energy and the chiral nematic free
energy. On the other hand, the pitch of the helical state is strongly affected
by the nemato-elastic coupling. As a result this state is not efficient in
minimizing the chiral nematic free energy.Comment: 7 pages, 2 eps figure
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