Supramolecular gels based on organic diacid monoamides of cholesteryl glycinate

The effect of meta versus para substitution on the aggregation of bis-cholesteryl appended 2,6-disubstituted pyridine-based gelators

The self assembly of bent core isomers comprising pyridine-cholesteryl units connected through meta- and para-substituted benzene as linkers were studied and their gelation and aggregation phenomena were compared with respect to the substitution effect.

Novel Tri-Cholesteryl Derivatives-Based Low Molecular Mass Organic Gelators with Multi-Stimuli Responsive Properties

Two novel tri-cholesteryl derivatives 1 and 2 have been designed and prepared. Gelation tests in 30 liquids revealed that 1 is a more efficient gelator than 2. Interestingly, the gel of 1/cyclohexane shows a reversible sol–gel phase transition in response to a variety of disparate stimuli such as temperature, stress, and HCl gas. In particular, a fully reversible thixotropic property was observed, which has been rarely reported before. Fourier transform infrared spectroscopy and 1H NMR measurements revealed that hydrogen bonding is an important driving force for the formation of the gel networks. The network structures of 1 and 2 in their cyclohexane gels were studied by scanning electron microscopy and X-ray diffraction analyses, and possible packing models were proposed accordingly. The findings demonstrated in the present work suggest that there is a big potential for developing tri-cholesteryl derivatives into extraordinary low molecular mass gelators.

Biodegradable, multiple stimuli-responsive sodium deoxycholate–amino acids–NaCl mixed systems for dye delivery

Multiple stimuli-responsiveness of NaDC–amino acid–NaCl mixed systems.

New triangular steroid-based A(LS)3 type gelators for selective fluoride sensing application

A new series of triangular steroid-based A(LS)₃ type gelators has been developed which exhibited selective fluoride sensing abilities. The gelation, self-assembly and anion sensing properties of these gelators could be controlled by systematically altering their molecular structures.

Novel dimeric cholesteryl derivatives and their smart thixotropic gels

Three novel LS(2)-type dimeric-cholesteryl derivatives (1-3), where S is a steroidal residue and L stands for a linker connecting the two S residues and contains three benzene rings and two amide and two carbamate groups, were designed and prepared. The compounds can gel a wide variety of organic solvents via three different ways, including mixing at room temperature, a heating-cooling cycle, and ultrasound treatment. SEM measurements revealed that the structures and the concentrations of the gelators, the nature of the solvent, and the preparation method employed have a great effect on the morphologies of the gel networks. It was revealed that 1 is a supergelator for DMSO (cgc = 0.04% w/v) and that the 1/DMSO gel can be prepared via any of the three methods mentioned above. Furthermore, the gel possesses excellent mechanical strength and a very smart thixotropic property. FT-IR and temperature- and concentration-dependent (1)H NMR spectroscopy studies revealed that hydrogen bonding and π-π stacking among the molecules of 1 are two important driving forces for the physical gelation of DMSO. In addition, XRD analysis confirmed the layered packing structure of 1 in its DMSO gel.

Design, synthesis and stimuli responsive gelation of novel stigmasterol-amino acid conjugates

An efficient synthesis of three novel stigmasterol-amino acid (glycine, L-leucine and L-phenylalanine) conjugates as stimuli responsive gelators is reported. The gelation properties of the prepared compounds were investigated in a variety of organic as well as aqueous solvents. The most striking finding of our investigation was that the hydrochloride salts of the prepared conjugates acted as gelators, whereas the neutral conjugates were either non-gelators or formed only a weak gel in anisole. The hydrochloride salts of stigmasteryl glycinate and L-leucinate form gels in n-alcohols (n=4-10) and in ethane-1,2-diol, and that of stigmasteryl L-phenylalaninate forms gels in aromatic solvents and in tetrachloromethane. These unique properties of the gelators were explored to prepare stimuli responsive, "acid-base" triggered reversible sol-gel transitions. The gelators and their gels were characterized by liquid and solid-state NMR as well as FT-IR. The morphology of their corresponding xerogels was investigated by SEM.

Glucose-based fluorescent low-molecular mass compounds: creation of simple and versatile supramolecular gelators

Five novel glucose-based naphthalene derivatives with linkers containing hydrazine, ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, and 1,6-hexanediamine, respectively (1, 2, 3, 4, and 5) were designed and prepared. The gelation test revealed the following points: (1) within the 30 solvents tested, 1 gels water only; (2) in contrast, 2 gels not only water, but also 11 of the organic solvents tested, a typical "ambidextrous gelator"; (3) 3, 4, and 5, however, gel organic solvents only, and the numbers of solvents gelled are 11, 11 and 13, respectively. Clearly, these compounds are effective low-molecular mass gelators, and show transitions from a low-molecular mass hydrogelator to an ambidextrous gelator and then to low-molecular mass organogelators with a slight increase in the length of the spacers. Interestingly, 5 is a super gelator to acetonitrile, of which the minimum gelation concentration is only 0.07%, w/v. The morphology, microstructure and molecular aggregation of the system strongly depend on the transition, as revealed by SEM, contact angle, energy dispersive X-ray spectroscopy, and XRD measurements. More interestingly, an aggregation-induced enhanced emission was observed along with gelation. Furthermore, the system appeared as a supramolecular chiroptical switch in the sol-gel process that is the chirality disappeared when the gel was heated to solution, whereas it reappeared when cooled to a gel.