ELASTICITY AND PHASE-BEHAVIOR OF NEMATIC ELASTOMERS

We describe the molecular basis of unusual phenomena displayed by nematic networks including phase transitions, spontaneous shape changes, discontinuous stress-strain relations, and nonlinear stress-optical laws. Such rubbers are composed of polymer chains of stiff rods either linked by flexible spacers to form a backbone polymer or, in the case of comb polymers, linked as pendants. We describe the polymers as wormlike chains in a nematic field. We also calculate deviations from classical behavior of conventional (nonnematic) elastomers due to residual nematic interactions.