FLUCTUATIONS AND LONG-RANGE ORDER IN SMECTIC ELASTOMERS

In a crosslinked polymer network, which has a lamellar or liquid cryst alline smectic-A order, layer deformations are penalized by an underly ing rubber elasticity. By integrating out phonon modes of the network, we obtain an effective smectic-A elastic free energy in which there i s an energy cost for rotating smectic layers relative to the elastic n etwork. As a result, there is long-range translational smectic order w ith true Bragg peaks in the X-ray scattering intensity with Debye-Wall er factors depending on the crosslink density of the network. There is also a very anisotropic diffuse scattering.