Synthesis and Characterization of a Novel Liquid Crystalline Polymer Showing a Nematic Columnar to Nematic Discotic Phase Transition

Abstract

A novel liquid crystalline polyacrylate, exhibiting a nematic columnar and a nematic discotic phase, the latter not found in any polymer previously, has been synthesized using a polymer analogous reaction, substituting the discotic mesogens on a reactive polymer. The highly flexible concept of the polymer analogous reaction enables us to introduce structural variations and to create and control molecular architectures. The mesophases of polymer 1, bearing the pentakis(methylphenylethynyl)benzene mesogen via a flexible undecanoxy spacer, as well as its low molar weight homologue 2, were fully characterized by optical polarizing microscopy, differential scanning calorimetry and powder X-ray diffraction. The thermal behavior of both compounds is qualitatively similar. Both materials exhibit a nematic discotic phase (N D) at higher temperatures, which is unique for the polymer, as this phase has only been observed in low molar mass materials so far. At lower temperatures 2 crystallizes, whereas 1 undergoes a transition into the nematic columnar phase (Ncol).

Gold‐Catalyzed Intermolecular Addition of Carbonyl Compounds to 1,6‐Enynes: Reactivity, Scope, and Mechanistic Aspects

“…Table 3 lists the structure spacings obtained from the respective diffractograms for the whole set of copolymers A1 – A4 . The X‐ray pattern of the copolymers is compatible with a nematic columnar mesophase 56. The lowest spacing corresponds to the planar distance between disks ( d 001 ), whereas the higher ones ( d 100 , d 200 ) correspond to the lateral distance between columns.…”

Multiple glass transitions in the plastic crystal phase of triphenylene derivatives

“…The molecular architecture of DLC typically comprises a rigid, aromatic core like a triphenylene [1,2] or a pentakis(methylphenylethynyl)benzene unit [3], which is laterally substituted by several flexible tails. Due to their disk-shaped mesogenic units, DLC form specific mesophases that range from various nematic structures (nematic discotic, N D nematic columnar, N Col ), having only orientational order, to hexagonally arranged columnar phases (Col h ) characterized by two-dimensional positional order.…”

Stable, Low‐Temperature Discotic Nematic Superstructures by Incorporating a Laterally Substituted Sidearm in Hexakis(phenylethynyl)benzene Discogens

“…Taking into account the POM and XRD results, a discotic nematic phase was unequivocally assigned to the mesophase of 2-10. This assignment was further supported by the considerably small mesophase-to-isotropic transition enthalpies that were similar to those values for discotic nematic phases [13,15] and significantly smaller than values for columnar nematic phases. [12c,16] Triphenylene compounds have the advantage of showing absorption at wavelengths shorter than 400 nm, rendering them transparent in the visible region, which is important for applications as compensating films.…”