Porous organosilicates by non-hydrolytic sol-gel routes
| Authors | |
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| Year of publication | 2013 |
| Type | Conference abstract |
| MU Faculty or unit | |
| Citation | |
| Description | New non-hydrolytic sol-gel reactions providing hybrid organosilicate materials containing various polyphenolic structural motifs were developed. Mesoporous gels are formed in polycondensation reactions of multifunctional phenols, such as hydroquinone, 4,4-dihydroxybiphenyl, bisphenol A, and phloroglucinol with silicon(IV) acetate in polar ether solvent. Acetic acid was identified as a byproduct in elimination reactions. Xerogels were obtained by drying under vacuum. The produced materials contain residual acetoxy and phenolic hydroxyl groups allowing for subsequent grafting and surface modification. An impact of the employed spacer molecules and reaction conditions on the degree of condensation and xerogel porosity was studied. The condensation degree was established by gravimetric techniques and appears to be independent of reaction temperature but strongly depends on the nature of the spacer molecules. Hydroquinone provided gels with the highest value of 91%. The surface area of xerogels depends both on reaction temperature and the nature of polyphenolic ligand. A higher reaction temperature leads to a larger surface area. Phloroglucinol provided a xerogel with 790 m2/g of surface. Additionally a study of grafting of organic groups on the gel surface by the reactions with alcohols and phenols and anchoring of aluminum species by treating the gels with compounds such as aluminum alkyls AlR3 and aluminum halides AlX3 was performed. All the prepared xerogels and modified materials were characterized by elemental analyses, solid-state 13C, 27Al, and 29Si NMR, IR spectroscopy, surface area analysis, thermal analysis TG/DSC, and XRD. |
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