Recent Advances on Supramolecular Gels: From Stimuli-Responsive Gels to Co-Assembled and Self-Sorted Systems

Abstract

Gels prepared from low-molecular-weight gelators (LMWGs) represent versatile soft materials. Self-assembly of LMWGs forms nanofibers and above critical gelation concentrations, the entanglement of which leads to self-supporting gels. Owing to the dynamic properties of the self-assembly process, stimuli-responsive LMWGs have prospered in the last decade. In addition, incorporating multiple LMWGs into one system brings the opportunity to achieve sophisticated designs and functions. This review covers recent advances in the field of supramolecular gels, from stimuli-responsive gelators to multicomponent systems that are self-sorting and/or co-assembling.

Varying the hydrophobic spacer to influence multicomponent gelation

“…A subtle change in the intermolecular interactions can significantly influence the gel properties; perturbation of non-covalent forces may even lead to destruction of gels and formation of sols. 5 In spite of reasonable progress in gel chemistry, it is still a difficult task to design molecules that form gels. 4 Although computational techniques have been developed to predict gelation propensities of compounds, their use is still limited.…”

“…6 As an alternative approach, it is common to adapt the properties of known gelators by following different approaches: first, by varying the route of self-assembly, specifically the self-assembly kinetics, keeping the final composition of the material identical; 4,7 second, by exposing a pre-formed gel to an external stimulus like heat, pH, UV-light, or ions to thereby modify its properties. ; 5,8 third, by varying the chemical structure of the gelator. 9 Compounds with very similar chemical structures may have significantly different gel properties.…”

“…10 A fourth approach, which has been getting increasing interest in recent years, is to synthesize multicomponent gels by mixing of two or more gelator building blocks. 5,11 Multicomponent gels have several advantages over single component systems. The properties of multicomponent gels can often not be predicted from either of the individual components.…”

Making and Breaking of Gels: Stimuli-Responsive Properties of Bis(Pyridyl-N-oxide Urea) Gelators

“…The stimuli-responsive properties of LMWGs [1][2][3][4][5]56] were studied in the presence salts/ions, for example, making or breaking of the gel network. Xu et al have synthesized an organogel with pyrene fluorophore and urea-sulfonamide anion binding sites to show the effect of ion s size in gelation [57].…”

“…Stimuli-responsive low molecular weight gelators (LMWGs) [1][2][3][4][5] are an excellent class of soft materials because the gelation properties can be switched on/off by an external stimulus, such as heat, light, sound, redox, pH, and salts/ions. These semi-solid materials with unique physical properties display various applications [6][7][8][9][10][11][12][13] in catalysis, cell culture, crystal growth media, drug delivery, tissue engineering, and sensing and dynamic gels.…”