Compressible porous hybrid monoliths: preparation via a low molecular mass gelators-based gel-emulsion approach and exceptional performances

Abstract

A cholesteryl derivative, BuDphe, which is a low molecular mass gelator (LMMG), was synthesized and used as a stabilizer for the creation of a number of water/oil gel-emulsions, of which the oil could be a mixture of butyl methacrylate (t-BMA) and p-divinylbenzene (DVB), a mixture of t-BMA, DVB and polydimethylsilane (PDMS), or that of t-BMA, DVB, PDMS and trimethoxymethylsilane (MTMS). Polymerization of these mixtures resulted in porous polymeric or hybrid monoliths, M-1, M-2, M-3, M-4 and M-5, respectively, of which the first is a pure poly-t-BMA monolith, the second to the fourth ones contain an increasing amount of PDMS, and the last is a hybrid of poly-t-BMA, PDMS and hydrolyzed MTMS. The hybrid monoliths, in particular M-5, as prepared possess not only hydrophobicity, porosity, and low-density, but also an unprecedented flexibility in the dry state with a maximum shape recovery corresponding to 100% of the original thickness after more than 70% compression strain. Moreover, silylanization also improves the thermo-stability of the porous materials. An absorption test demonstrated that M-5 is an excellent absorbent for a number of organic solvents and oils. The material after absorption can be re-generated and the liquids absorbed can be recovered by simple squeezing. Furthermore, the absorption-separation process with CH₂Cl₂ as an example solvent could be repeated at least 10 times with no significant reduction of its absorption capacity. Combination of the excellent flexibility, great absorptivity, easiness in preparation, and low-energy consumption in drying makes the hybrid monoliths, in particular M-5, possess the potential to find real-life applications.