synthesized a rigid rod epoxy monomer containing the long mesogenic unit
of biphenyl and the aromatic ester group.
The two signals centered at 4.42 and 4.24 ppm correspond to the two methylenic carbon c' protons in the modified monomeric unit; the signal centered at 3.90 ppm corresponds to the methylene attached to the oxygen in the alkyl chains of the mesogenic unit
and to the methynic proton b'.
Figure 4 presents the molecular model of the mesogenic unit
of HBA-ETP (37, 38) and Fig.
The diol monomer was designed to carry the mesogenic unit
, which was selected to be the cyanobiphenyl group to produce materials with a strong dipole positioned along the long axis of the mesogenic unit
Dielectric response of liquid crystalline epoxy compounds is quite complex due to the presence of polar, rigid mesogenic units
. It is known that dielectric spectra of a liquid crystal consist of different relaxation processes which depend on the direction of the electric field with respect to the orientation of the mesogens.
The literature describes various ways of modifying the resins in order to improve their elasticity: introduction of substituents into the mesogenic units
, (5) introduction of a flexibility spacer between the mesogenic units
, (6,7) introduction of a flexibility spacer which decouples the reactive end-functional group from the rigid-rod mesogenic group, (8) or curing reaction of rigid-rod mesogenic epoxy monomers with aliphatic dicarboxylic acids.
Blumstein, "Mematic and chlosteric thermotropic polyesters with azoxybenzene mesogenic units
and flexible spacers in the main chain, " J.
Comparison of the properties of aromatic polyesters with different mesogenic units
and a common flexible spacer," Journal of Polymer Science A-1, Polymer Chemistry, vol.
Xu, "Synthesis, characterization and properties of high molecular weight poly(butylenes succinate) reinforced by mesogenic units
," European Polymer Journal, vol.
In this study, we synthesized a novel LC dicarboxylic acid curing agent (DACA), which is composed of 2,6-naphthalene and 1,4-phenylene mesogenic units
. LCTs of DACA and epoxy resins with different functionalities were prepared, and 2-methyl imidazole (2MI) was used as a catalyst.
It has been indicated that the degree of overlapping between two mesogenic units
depends on their spacer lengths.
Liquid crystalline epoxies, which contain rigid mesogenic units
in place of the kinked and flexible structure of bisphenol-A, can be cured so that the resulting network has a liquid crystalline structure consisting of ordered domains of various sizes.