Self‐Assembled Fibers Containing Stable Organic Radical Moieties: Alignment and Magnetic Properties in Liquid Crystals

Abstract

Macroscopically oriented stable organic radicals have been obtained by using a liquid-crystalline (LC) gel composed of an l-isoleucine-based low molecular weight gelator containing a 2,2,6,6-tetramethylpiperidine 1-oxyl moiety. The LC gel has allowed magnetic measurements of the oriented organic radical. The gelator has formed fibrous aggregates in liquid crystals via intermolecular hydrogen bonds. The fibrous aggregates of the radical gelator are formed and oriented on cooling by applying a magnetic field to the mixture of liquid crystals and the gelator. Superconducting quantum interference device (SQUID) measurements have revealed that both oriented and nonoriented fibrous aggregates exhibited antiferromagnetic interactions, in which super-exchange interaction constant J is estimated as -0.89 cm(-1) .

Functional Liquid Crystals towards the Next Generation of Materials

“…[163] Since the solvents are anisotropic for these materials,c ooperation of liquid crystals and selfassembled fibers leads to the enhancement of properties and the induction of new properties.T he electrooptical and magnetic properties of the anisotropic gels based on nematic and cholesteric liquid crystals have been examined. [176][177][178][179][180] Mixtures of polymerizable lysine-based gelator 24 and an ematic liquid crystal, 4-cyano-4'-pentylbiphenyl (5CB), are applied for the formation of fibrous polymerized networks (Figure 7c). [178,179] These polymerized LC gels show improved light-scattering properties compared with non-polymerized LC gels.A ligned self-assembled fibers of organic radical gelators exhibiting magnetic properties were also developed.…”

“…[178,179] These polymerized LC gels show improved light-scattering properties compared with non-polymerized LC gels.A ligned self-assembled fibers of organic radical gelators exhibiting magnetic properties were also developed. [180] Photo-responsive properties have been exploited for nematic liquid crystals for the past three decades. [72,181,182] Fore xample,p olarized light was used as an external stimuli for the alignment of nematic liquid crystals.…”

p‐Quaterphenylene as an Aggregation‐Induced Emission Fluorogen in Supramolecular Organogels and Fluorescent Sensors

“…[1][2][3][4][5][6][7][8][9] To enhancet he stabilitya nd robustness of the sophisticateda ssemblies, multi-noncovalenti nteractions should be delicately incorporated by rational design on am olecular scale. [10][11][12][13][14] Various noncovalent interactions (such as hydrogen bonding, p-p stacking,a nd van der Waals forces) have been utilized to hold the small buildingb locks together, [15,16] and numerous artificial supramolecular architectures of different sizes, shapes, and functions have been achieved, [17][18][19][20][21][22][23][24][25][26] among which gelation is ap owerful methodl eading to welldefined supramolecular nanostructures. The gelation process generally involves hierarchical self-assembly of the gelator molecules to form long, fibrousa ggregates, followed by further entanglementf orming as olid-like matrix that traps solvent within the 3D network.…”

Functional liquid-crystalline polymers and supramolecular liquid crystals

“…260,261 Other functional LC physical gels have been prepared. 241,242,[262][263][264][265][266] For example, a triphenylene columnar LC gel have been reported to show charge carrier transport. 264 Remarkably, the gelated columnar structure exhibits improved transport abilities compared to the pure discotic liquid crystal due to the repression of molecular fluctuations, which increases the columnar order and the hole mobiles.…”

“…In this case, gelators bearing 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) groups have been utilized. 262,263 Use of photofunctional gelators bearing azobenzene groups leads to the photoswitching of the LC gel structures. 267,268 CONCLUSIONS An overview of the development of functional LC polymers are described in this review.…”