Abstract:

Calixarenes, as the third generation of host molecules in supramolecular chemistry due to their facile modification and unique molecular or ion recognition ability, have received great attention during the last few decades. In the present work, three carboxyl acid-appended calix[4]arene derivatives were prepared. The compounds are characterized by four tert-butyl groups appended at the upper rim of the main body of the compounds, and one, two or four carboxyl acid moieties appended at the lower rim, of which they are denoted as CMA, CDA and CTA, respectively. The as-prepared compounds possess surfactant-like structure but insoluble in water. Gelation tests reveal that the compound with more carboxyl groups shows stronger gelation ability. For example, among the seventeen organic liquids and ten monomeric liquids tested, CTA gels seven of them, CDA gels one of then, but CMA and the control C4, which possesses none of the carboxyl acid structure, gel none of them. Further studies demonstrate that the CTA gels with monomeric liquids as solvents have good heat reversibility and can be emulsified with water, resulting in gel-emulsions. Polymerization of the gel-emulsions results in low density polymeric monoliths with porous internal structures. Preliminary test shows that the porous materials as produced are good adsorbents of organic liquids such as benzene, and heavy metal ions such as Cr(Ⅲ). Moreover, the materials can be reused via simple washing and drying process and have potential application in water purification.

Key words: calix[4]arene derivatives, low-molecular mass gelators, molecular gels, gel-emulsions, porous polymeric monoliths