Polygonal Cylinder Phases of 3-Alkyl-2,5-diphenylthiophene-Based Bolaamphiphiles: Changing Symmetry by Retaining Net Topology

Abstract

Novel bolaamphilic triblock molecules consisting of a bent 2,5-diphenylthiophene unit, two terminal glycerol units, and a lateral n-alkyl chain have been synthesized via Ni-and Pd-catalyzed coupling reactions as key steps. The thermotropic liquid crystalline behavior of these compounds was investigated by polarized light optical microscopy, DSC, and X-ray scattering and the influence of the length of the lateral alkyl chains on the mesomorphic properties was studied. With elongation of the lateral alkyl chains, three different columnar phases (Col squ /p4mm, Col squ /p4gm and Col hex /p6mm), representing polygonal cylinder structures were found, where the cells have a square, pentagonal, and hexagonal cross-section, respectively. In the observed phase sequence, the change of the net topology is the same as seen for related linear biphenyl derived bolaamphiphiles, but the symmetry is increased, i.e, rectangular phases are replaced by square lattices.

Hydrogen Bonding for Supramolecular Liquid Crystals

“…In order to realize practical applications of these complex LC phases, for example to organize π-conjugated aromatics into functional organic electronic devices [153][154][155][156], series oligothiophene-based bolaamphiphiles are studied [157][158][159]. Because oligothiophenes are an interesting class of organic semiconductors Reproduced from Ref.…”

“…[136] by permission of The Royal Society of Chemistry [160][161][162][163][164][165][166][167][168][169][170][171], their derivatives have been employed as active layers in field-effect transistors (FETs) [172][173][174] and in p-n-hetero-junctions with ZnO nanowires in solar cells [175]. For one thiophene-based bolaamphilic triblock molecules consisting of a bent 2,5-diphenyl thiophene unit, two terminal glycerol units, and a lateral n-alkyl chain [158], it is observed that with the elongation of the lateral alkyl chains, three different columnar phases (Col squ /p4mm, Col squ /p4gm, and Col hex /p6mm), representing polygonal cylinder structures, were found, in which the cells have a square, pentagonal, and hexagonal cross section, respectively (Fig. 5.26).…”

Synthesis and self-assembly behavior of 2,5-diphenylethynyl thiophene based bolaamphiphiles

“…The phase transition temperatures and associated enthalpy values of the synthesized compounds 1ET/n together with the previously reported compounds 1T/n [9] and 1EP/n [17] are summarized in Table 1. Compounds 1ET/n are all crystals without liquid crystalline properties in their pure states.…”

“…[7,8,5]. In order to introduce functionality into such soft nanostructures for their potential applications, oligothiophene segments [9][10][11][12][13] and ethynlene [14] units have been employed respectively as rod-like building blocks. Till now honeycomb-type columnar phases with triangular, square, and hexagonal cells have been found for functional bolaamphiphiles based on bithiophene [10b,11], tetrathiophene [10a,12] and sexithiophene [13] cores by varying the length and number of the lateral alkyl chains, and recently even the honeycomb-type columnar phase with noncentrosymmetric trigonal p3m1 symmetry (Col hex-3 /p3m1), which is of potential interest for nonlinear optics applications [15] has been found for bolaamphiphiles with p-conjugated 1,3-bis(ethynyl)benzene bent-core [16,17].…”

“…As part of our research work on functional bolaamphiphiles, herein we have further introduced both thienyl and acetylene units into the rigid core simultaneously and obtained a new series of bentshaped 2,5-diphenylethynyl thiophene based bolaamphiphiles 1ET/n and compared them with the related compounds 1T/n [9] without ethynyl units and compounds 1EP/n [17] with phenyl instead of thienyl as the central unit in the rigid core (see Scheme 1).…”