Liquid crystal elastomer balloons

We describe a setup for mechanical measurements of smectic liquid crystal e lastomers and study two materials with different network topologies. The el astic response of macroscopically oriented smectic elastomers to a two-dime nsionally isotropic stress in the film plane is measured. The experimental method is based upon the measurement of the inner excess pressure of elasto mer balloons, produced by inflation of thin freely suspended films of the s mectic material to spherical shape and subsequent photo-cross-linking. We d iscuss the effects of entropic rubber elasticity and smectic layer compress ion in the experiment and analyze influences of the network topology (2D or 3D) on the elastic behavior.