Azomethine mesogens

Mallon JJ, Adams PM (1993) Synthesis and characterization of novel epoxy monomers and liquid crystal thermosets. J Polym Sci Polym Chem 31 2249-2260 Mija A, Cascaval CN (2009) Liquid crystalline epoxy thermoset with azomethine mesogen. Polimery 54 786-789... 

Solid-State Structures of a Homologous Series of Mesogenic Aromatic—Aliphatic Azomethine Ether Polymers... 

The solid state structure of a homologous series of mesogenic aromatic-aliphatic azomethine ether polymers (AZMEP-n), with n (=1-16) methylene spacers in the main chain, has been studied by X-ray fiber diffraction techniques. Unit cell parameters determined from the fiber patterns of heat-treated single filaments have been used to classify the polymers into distinct groups having different chain conformations and crystal systems. The even members of the. series, where n = 2 4, have C-centered monoclinic unit cells while the unit cells for polymers with n = 6 8 are I-centered monoclinic. When n is even and 10 the unit cells are (primitive) triclinic. The fiber repeat, in the triclinic cells correspond to one chemical moiety while in the monoclinic cells the fiber repeat corresponds to two chemical residues. In addition, the fiber repeat distances are consistent with the methylene spacers adopting an all-trans conformation for all even AZMEP-n polymers. 

BISWAS ET AL. Mesogenic Aromatic—Aliphatic Azomethine Ether Polymers 257... 

This paper deals with the study of the mechanism of orientation process, the guest-host effect and the elec-trohydrodynamic (EHD) instabilities in LC comb-like polymers with azomethine and cyandiphenyl mesogenic groups. 

Liquid crystals exhibit a partially ordered state (anisotropic) which falls in-between the completely ordered solid state and completely disordered liquid state. It is sometimes referred to as the fourth state of matter . In recent years, interest in liquid crystalline thermosets (especially liquid crystalline epoxy) has increased tremendously [33-44]. If the liquid crystal epoxy is cured in the mesophase, the liquid crystalline superstructure is fixed permanently in the polymer network, even at higher temperature. Liquid crystal epoxies are prepared using a liquid crystal monomer [33-38] or by chemical modification of epoxy resin [43] which incorporates liquid crystal unit in the epoxy structure. Liquid crystalline epoxy resins with different types of mesogen such as benzaldehyde azine [33], binaphthyl ether [34, 35], phenyl ester [36, 37] and azomethine ethers [38, 39] have been reported. Depending on the chemical nature of the mesogen, the related epoxies display a wide range of thermomechanical properties. The resins can be cured chemically with an acid or amine [40, 41] or by photochemical curing in the presence of a photo-initiator [3]. Broer and co-workers [42] demonstrated the fabrication of uniaxially oriented nematic networks from a diepoxy monomer in the presence of a photo-initiator. 

Mieczkowski, J. Szydlowska, J. Matraszek, J. Pociecha, D. Gorecka, E. Donnio, B. Guihon, D. Bent-shaped mesogens without an azomethine joint J. Mater. Chem. 2002,... 

However, despite showing promising thermal stability, this type of mesogen fell from widespread use simply because the azomethine linkage (-CH = N-) imparts colour to the material and proved too sus-... 

Marin L, Zabulica A, Sava M (2013) Symmetric liquid crystal dimmers containing a luminescent mesogen synthesis, mesomorphic behavior, and optical properties. Soft Mater 11 32-39 Shukla U, Rao KV, Rakshit AK (2003) Thermotropic liquid-crystalline polymers synthesis, characterization and properties of poly(azomethine esters). J Appl Polym Sci 88 153-160 Shukla SR, Harad AM, Mahato D (2006) Depolymerization of nylon 6 waste fibers. J Appl Polym Sci 100(1) 186-190... 

Vasanthi BJ, Ravikumar L (2013) Synthesis and characterization of poly(azomethine ester)s with a pendent dimethoxy benzylidene group. Open J Polym Chem 3 70-77 Zifa L, Zhang S, Shaokui CAO, Chen Z, Zhou Q (1996) Synthesis and characterization of liquid crystal polymers with T-shaped two-dimensional mesogenic units. Chin J Polym Sci 14 (l) 71-79... 

Mormann W, Broche M, Schwarz P (1997) Mesogenic azomethine based diepoxides— monomers for the synthesis of liquid crystal thermoset networks. Macromol Chem Phys 198 3615-3626 Mossety-Leszczak B, Wlodarska M (2011) Liquid crystallinity in polymers—liquid crystalline epoxy resins. In Iwan A, Schab-Balcerzak E (eds) Liquid crystalline organic compounds and polymers as materials of the XXI century from synthesis to applications. Transworld Research Network, Kerala... 

The former mesogen was utilized in combination with polyesters which give nematic structures in the melt, with the exception of the / -terphenyl-containing polyester that shows a smectic C phase. The latter optically active mesogen was used in combination with the nematogenic azomethine polymer and with the /7-terphenyl polyester. The last polymer displays, on admixture over a significant range of composition, a twisted smectic C phase, whereas induced cholesteric structures were observed in all other cases. ... 

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