A second columnar liquid crystalline phase formed by polymers with highly tapered side chains

Previous work has shown that polymethacrylates with highly tapered side gro ups, such as poly{2-{2-[2-(2-methacryloyloxy ethoxy)-ethoxy]ethoxy}ethyl-3, 4,5-tris-(p-dodecyloxy-benzyloxy)benzoate} (H12-ABG-4EO-PMA), form columnar hexagonal (Col(h), previously designated phi(h)) liquid crystalline struct ures. The small angle X-ray data for drawn fibers of H12-ABG-4EO-PMA, and a lso those of its hydroxy-terminated monomer precursor and decyloxy-homologu e, contain several weak equatorial Bragg reflections in addition to those c haracteristic of the Col, phase. The intensities of these extra reflections decline progressively on heating and disappear before the temperature of t he Col(h)-to-isotropic transition is reached. It is proposed that the as-dr awn fibers contain a second phase, which is probably a columnar liquid crys talline structure in view of the decreases in the observed d-spacings with increasing temperature. The additional reflections are indexed by a two dim ensional monoclinic lattice, which probably contains columns with elliptica l cross-section. The lower symmetry is consistent with the formation of a t ilted columnar phase analogous to those formed by certain low molecular wei ght discotic materials.