Calix[4]arene-based low molecular mass gelators to form gels in organoalkoxysilanes

Abstract

Three calix[4]arene derivatives (CMA, CDA and CTA) appended with one, two or four carboxyl acid structures were prepared. Gelation behaviours of the compounds and calix[4]arene itself in ten common organoalkoxysilanes were studied. It was found that at a concentration of 2% (w/v), only the compound with the most carboxyl groups (CTA) functions as a gelator, and only this compound gels with three of the liquids tested; however, the as created gels possess smart thixotropic and thermo-reversible phase transition properties. In particular, the CTA/trimethoxyphenylsilane (PTMS) gel exhibits superior mechanical strength with a storage modulus (G′) greater than 1.9 × 10⁶ Pa and a yield stress exceeding 3600 Pa at a concentration of 6.0% (w/v). Further testing demonstrated that the gel could be used as a substrate for sensing film fabrication, injection molding and melting-free deposition molding. Moreover, the objects from the molding and fabrication could be turned into permanent structures through further hydrolysis and condensation reactions. It is believed that the LMMGs based organoalkoxysilane gels have the potential to be used as smart materials for 3D printing and pre-cursors to a functionality-oriented solid matrix.