the twofold symmetry axis and perpendicular to it. Thus, both refractive indices are large, and An is small. With an applied field E > E", the sample switches to the bistable blue surface-stabilized structure with markedly increased birefringence. This texture appears to have the layers normal to the surfaces (6 = 0, parallel to the applied field) (Fig. 5B) . The system is driven to this bookshelf layer geometry by the tendency of the polarization to orient parallel to the applied field.

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... the polarization is in the layer plane, this preferred orientation of the polarization parallel to the field cannot be achieved with tilted layers. The "straightening" of tilted layers in this case is similar to the formation of quasibookshelf alignment with chevron SmC* materials upon application of large electric fields and is not surprising (20). The bistable nature of the bookshelf-aligned system is in accord with the "monostable" behavior of the known AFE SmCP phases and is evidence that director alignment parallel to the surfaces is preferred. The birefringence increase is due to the highly biaxial nature of the molecules and the phase. In the bookshelf geometry (Fig. 5B) , the conjugated aromatic units contribute to the polarizability only for light polarized along the director. All of the EO and current response characteristics of known B7 materials are consistent with a simplified model in which the B2 and B7 phases are actually diastereomeric SmCP structures, as shown in Fig. 2 . The classic bow-phase mesogens in the B2 phase form an AFE SmC,P, racemate, and other known B7 materials are AFE SmC,P, conglomerates. By using interlayer clinicity as a stereochemical control element, we have created a bow-phase mesogen exhibiting a conglomerate SmC,P, structure with desirable FE order. However, the natural rule requiring at least one twofold symmetry axis normal to the director in smectic liquid crystals remains apparently intact.