Discotic liquid crystals of transition metal complexes 58†: Novel phthalocyanine-based mesogenic monomers and polymers exhibiting spontaneous homeotropic alignment and helical tetragonal columnar structure

Two synthetizations of a novel series of phthalocyanine-based discotic liquid crystals substituted by a polymerizable group, acryloyl group or a norbornene group: 2-(12-acryloyloxydodecyloxy)-3-methoxy-9,10,16,17,23,24-hexalcis (3,4-dialkoxyphenoxy)phthalocyaninato copper(II) [abbreviated as (n,12)PcCu(OCH3)(Acryloyl) (7: e (n = 10), f (n = 12), g (n = 14))] and 2-(12-norborn-2-enecarbonyloxydodecyloxy)-3-methox y-9,10,16,17,23,24- hexalcis(3,4-dialkoxyphenox y)-phthalocyaninato copper(II): [abbreviated as (n, 12)PcCu(OCH3)(Norb) (9e, f, g)]. Their liquid crystalline properties and homeotropic alignment were investigated using a polarizing microscope, a differential scanning calorimetry (DSC), and a temperature-variable X-ray diffractometer. As a result, each of the derivatives gave a Col(tet), mesophase in the higher temperature region, displaying perfect homeotropic alignment between the two glass plates. In order to obtain the thin film while keeping their homeotropic alignment at room temperature, attempts to polymerize the monomers, 7 and 9, in the Col(tet), phase showed homeotropic alignment. The polymerization of the acryloyl-substituted monomers (7) was not successful in any of the methods, whereas the polymerization of norbornene-substituted monomers (9) was quite successful by ring-opening metathesis polymerization with a Grubbs catalyst to obtain the novel polymers, poly-(n, 12)PcCu(OCH3)(Norb) (10e, f, g). Each of the polymers (10) were found to show a perfect homeotropic alignment from room temperature to ca. 200 degrees C of the decomposition temperature. Moreover, it was also revealed from temperature-variable small-angle X-ray diffraction studies that each of the polymers 10 showed a helical Col(tet), (helical tetragonal columnar) structure. The helical Col(tet), phase structure may be able for use in organic electroltuninescent devices and solar cells in the future.

Automated summary

Two novel series of phthalocyanine-based discotic liquid crystals substituted by a polymerizable group, acryloyl group or a norbornene group were synthesized and investigated for their liquid crystalline properties and homeotropic alignment. The derivatives showed perfect homeotropic alignment and successful polymerization of norbornene-substituted monomers led to the formation of polymers with a helical Col(tet) structure, which may have potential applications in organic electroluminescent devices and solar cells in the future.