ABSTRACT
1,3:2,4-Dibenzylidene-d-sorbitol (DBS), a simple, commercially relevant compound, was found to self-assemble as a result of intermolecular noncovalent interactions into supramolecular gels in deep eutectic solvents (DESs) based on choline chloride combined with alcohols/ureas. DBS formed gels at a loading of 5 % w/v. Rheology confirmed the gel-like nature of the materials, electron microscopy and X-ray diffraction indicated underpinning nanofibrillar DBS networks, and differential scanning calorimetry showed the DES nature of the liquid-like phase was retained. The ionic conductivities of the gels were similar to those of the unmodified DESs, thus proving the deep eutectic nature of the ionic liquid-like phase. Gelation was tolerant of ionic additives Li+ , Mg2+ , and Ca2+ ; the resulting gels had similar conductivities to electrolyte dissolved in the native DES. The low-molecular-weight gelator DBS is thus a low-cost additive that forms gels in DESs from readily available constituents, with conductivity levels suitable for practical applications.
ABSTRACT
Dibenzylidene-D-sorbitol (DBS) has been a well-known low-molecular-weight gelator of organic solvents for over 100 years. As such, it constitutes a very early example of a supramolecular gel--a research field which has recently developed into one of intense interest. The ability of DBS to self-assemble into sample-spanning networks in numerous solvents is predicated upon its 'butterfly-like' structure, whereby the benzylidene groups constitute the 'wings' and the sorbitol backbone the 'body'--the two parts representing the molecular recognition motifs underpinning its gelation mechanism, with the nature of solvent playing a key role in controlling the precise assembly mode. This gelator has found widespread applications in areas as diverse as personal care products and polymer nucleation/clarification, and has considerable potential in applications such as dental composites, energy technology and liquid crystalline materials. Some derivatives of DBS have also been reported which offer the potential to expand the scope and range of applications of this family of gelators and endow the nansocale network with additional functionality. This review aims to explain current trends in DBS research, and provide insight into how by combining a long history of application, with modern methods of derivatisation and analysis, the future for this family of gelators is bright, with an increasing number of high-tech applications, from environmental remediation to tissue engineering, being within reach.
