Publication details

Synthesis of Organosilicate Gels by Non-Hydrolytic Reactions of Silicon Acetate

Authors

PINKAS Jiří KEJÍK Martin MORAVEC Zdeněk BARNES Craig

Year of publication 2013
Type Conference abstract
MU Faculty or unit

Central European Institute of Technology

Citation
Description A non-hydrolytic sol-gel synthesis of new mesoporous organosilicate materials containing phenolic and bisphenolic structural motifs was developed. Xerogels are formed in polycondensation reactions of multifunctional phenols, such as hydroquinone, 4,4-dihydroxybiphenyl, bisphenol A, and phloroglucinol with silicon acetate in polar ether solvent. Acetic acid was identified as an elimination reaction byproduct. Xerogels were obtained upon drying in vacuo and the produced materials contain residual acetoxy and phenolic hydroxyl groups allowing for later grafting and surface modification. An impact of employed spacer molecule and reaction conditions on the degree of condensation and xerogel porosity was studied. Condensation degree was established by gravimetric techniques and appears to be independent of reaction temperature but strongly depends on the nature of the spacer molecule. Hydroquinone provided gels with the highest value of 91%. Surface area of xerogels depends both on reaction temperature and the phenol ligand. A higher reaction temperature leads to a larger surface area; phloroglucinol providing gel with up to 790 m2/g of surface. Additionally a study of grafting 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 AlR3 and 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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