Both increasing the Iso-to-Col transition and lowering the solidifying temperatures of a triazine-based dendrimer by introducing CN polar groups in the dendritic core

Abstract

The CN polarity in the linker effectively broadens the mesogenic range and lowers the solidifying temperature of the dendrimer.

Unconventional Approaches to Prepare Triazine-Based Liquid Crystal Dendrimers

“…As dendrimer 11 has already been observed to exhibit a columnar phase on thermal treatment, a strong CN polar group was incorporated in the central linker to investigate its influence on the mesogenic behavior. Dendrimers 15 and 16 were therefore further prepared for studying their LC properties ( Figure 10 ) [ 65 ]. Dendrimer 15 exhibited a columnar phase between ~102 and ~118 °C on heating and between ~115 and ~82 °C on cooling.…”

“…Intermolecular H-bond interactions can also be applied to prepare 1,3,5-triamino- s -triazine-based dendrimers with the columnar phase. Figure 13 shows an example of a central core with a C 2 symmetry that can be efficiently prepared according to the literatures [ 62 , 63 , 64 , 65 , 66 , 67 ]. Incorporating special functional groups at the periphery of dendrons can give desired physical properties to the LC triazine-based dendritic mixtures.…”

Converting non-Mesogenic to Mesogenic Stacking of Amino-s-Triazine-Based Dendrons with p-CN Phenyl Unit by Eliminating Peripheral Dipole

“…However, preparation of dimeric dendrimers with some particular functionality in the central linker may not be easy because of the steric effect from both dendronic halves. As we previously reported [48], the yields of the synthesis of dimeric dendrimers consisting of coupling two identical G-3 chloro-dendrons by means of N,N'dibenzylpropane-1,3-diamine based central linker are only about 35%. Therefore, in order to simplify the synthesis and improve the yields of DC liquid crystals, we turn our attention to dendron-precursors, by introducing a strong polar CN functionality to the dendritic skeleton and thus hoping to lead the dendrons to exhibit a broader mesogenic range on thermal treatment.…”

“…Surprisingly, though dendrimers as mesogens in liquid crystals have been extensively investigated because of their uniform packing and non-grained boundaries in the LC states [18][19][20][21][22][23][24][25][26][27][28][29][30], dendrons in the related studies are rather limited [31][32][33][34][35]. Possibly, dendrimers are rather symmetrical in chemical structures, which is advantageous for the easy formation of columnar phases [36][37][38][39][40][41][42][43][44][45][46][47][48][49]. The symmetrical structural feature favoring mesophase formation of dendrimers was adopted for several dendrons which self-assembled into dendrimers through H-bond interaction [50][51][52][53][54][55][56].…”

“…We previously demonstrated that the addition of phenyl-CN lateral units in the central linker of dimeric G-3 dendrimers not only effectively broadened the range of columnar phase but also lowered the temperature of solidification on cooling [48], which can be important on the point of view of further practical applications. Discotic columnar (DC) liquid crystals possess good self-assembling ability in a long-range domain; DC materials with broad mesogenic range should be useful as solvating candidates in opto-electronic devices [23,54,[57][58][59].…”