The Research Of Multistimuli Responsive Organogels Based On New Gelators Featuring Hydrazide And Anthraquinone

Organogels are composed of a self-assembled suprastructure of low molecular-mass organic gelators (LMOGs) through weak intermolecular interactions (such as hydrogen bonds etc) and a large volume of liquid immobilized therein. Because of their unique structures and wide applications in templated synthesis of nano-scale inorganic materials, oil recovery, organic soft materials, optical sensors, slow drug-delivery systems and so on, studies on organogels have been the subject of increasing attention in materials science and supramolecular chemistry in recent years. Recently, the development of "smart" or "responsive" gels has been especially appealing for potential applications. Thus, some examples on the sol-gel transition tuned by the environmental stimuli, such as light, ionic strength, electric or magnetic fields, mechanical stress, pH changes, molecular recognition and ultrasound have been reported.The reversible nature of supramolecular gels seems ideal for the use of stimulus-controlled catalytic systems by environmental stimuli.This paper contains the following sections:1 The synthesis of small molecule organic gels factor based on hydrazine, anthraquinone and study of its organic gel systemThe novel low-molecular-weight organogelators(LMOGs) lb-le composed of an anthraquinone unit, a hydrazide group, and long alkyl chains were synthesized. Studies on their structure-property relationship are intensified. They could form stable gels at concentrations as low as 0.1 wt% in tested solvents. Chloroalkanes and aromatic solvents tend to result in transparent gels, while alcohol and other solvents yield opaque gels. Interestingly, we further found that the achiral gelator could form supramolecular structures with well-defined helical ribbons. The FT-IR, PXRD, Uv-vis and 1H NMR spectral studies revealed that hydrogen bonding andπ-πinteractions were the main driving forces for formation of the gels. 2 This gel system of multi-responsive and its application:(1) Acid and Alkali Responsive PropertiesThe intermolecular hydrogen bond plays an important role in the forming gel process. By adding the TFA to the gel, the intermolecular hydrogen bonds can be damaged leading to the conversion of gel to the solution, and then adding TEA can return to gel state.(2) Anion Responsive PropertiesAlthough the hydrazide unit and the anthraquinone group were connected by the a-bond, the chloroform gel of lc could be changed into a red solution upon the addition of anion (F-, AcO- and H2PO4-) due to the disruption of the intermolecular hydrogen-bondings. Moreover, the red color clearly faded at once and the solution re-gelated upon the addition of methanol.(3) Ultrasound Responsive PropertiesAlthough compounds lc-le could not form gels in strong polar solvents, such as DMSO, methanol etc, Ultrasound promotes lc-le to form organogels when cooling its hot solution. The morphologies of the xerogels prepared from these gelators are strongly affected by ultrasound stimuli.(4) The application of organogelsThese organogelators could selectively gelate organic solvents from their mixtures with water. Furthermore, the xerogels prepared from the organogels showed a striking property of adsorbing dyes such as crystal violet from water. This dye-adsorption ability of gelators can be utilized in water purification by removing toxic dyes from wastewater.